retinol-acetate and Vitamin-A-Deficiency

The availability of synthetic vitamin A and its esters in unlimited quantities, has enabled populations around the world, consuming inadequate amounts of this vital micro-nutrient and hence subject to potential loss of sight or other manifestations of vitamin A deficiency, to have hope for a better future life. A technology exists for the preparation of synthetic vitamin A in various application forms. Many commonly-consumed foods may be used as carriers or vehicles of vitamin A to assure deficient populations of a sufficient intake of this antixerophthalmic and anti-infective vitamin.

Topics: Animals; Dietary Fats; Diterpenes; Edible Grain; Food, Fortified; Global Health; Humans; Margarine; Milk; Palmitates; Retinyl Esters; Sodium Chloride; Sodium Glutamate; Sucrose; Tea; Technology, Pharmaceutical; Vitamin A; Vitamin A Deficiency

Vitamin A (VA)-fortified rice is a potential intervention strategy to prevent VA deficiency in at-risk populations. Hot-extruded, triple-fortified rice grains with added VA, zinc, and iron were produced by hot extrusion technology and their ability to improve VA status was tested in Thai schoolchildren. The fortification levels were 10 mg of iron, 9 mg of zinc, and 1.05 mg of VA/g extruded rice. A paired stable isotope dilution technique with labeled ¹³C₂-retinyl acetate (¹³C-RID) was used to quantify VA pool size at the beginning and end of the feeding period. Fifty healthy schoolchildren with a serum retinol (SR) concentration of >0.7 μmol/L were randomly assigned to 2 groups to receive either triple-fortified rice (n = 25) or natural rice (n = 25) for 2 mo as part of the daily school meal. The fortified grains, mixed 1:50 with regular rice, were estimated to provide an extra 890 μg of VA/d, 5 d/wk. ¹³C₂-retinyl acetate (1.0 μmol) was administered orally to each child before and at the end of the feeding period to estimate total body reserves (TBRs) of VA, which increased significantly (P < 0.05) in the intervention group from 153 ± 66 μmol retinol at baseline to 269 ± 148 μmol retinol after 2 mo of feeding. There was no change in the TBRs of VA in the control group (108 ± 67 vs. 124 ± 89 μmol retinol) (P = 0.22). Serum retinol remained unchanged in both groups. We conclude that VA-fortified, hot-extruded rice is an efficacious vehicle to provide additional VA to at-risk populations, and that the efficacy of VA-fortified foods can be usefully monitored by the ¹³C-RID measurement of TBRs of VA but not by changes in SR concentration.

Topics: Carbon Isotopes; Child; Child, Preschool; Diterpenes; Double-Blind Method; Female; Food Handling; Food, Fortified; Humans; Iron, Dietary; Liver; Male; Oryza; Prevalence; Retinyl Esters; Risk; Seeds; Severity of Illness Index; Suburban Health; Thailand; Vitamin A; Vitamin A Deficiency; Zinc

In north India, vitamin A deficiency (retinol <0·70 μmol/L) is common in pre-school children and 2-3% die at ages 1·0-6·0 years. We aimed to assess whether periodic vitamin A supplementation could reduce this mortality.. Participants in this cluster-randomised trial were pre-school children in the defined catchment areas of 8338 state-staffed village child-care centres (under-5 population 1 million) in 72 administrative blocks. Groups of four neighbouring blocks (clusters) were cluster-randomly allocated in Oxford, UK, between 6-monthly vitamin A (retinol capsule of 200,000 IU retinyl acetate in oil, to be cut and dripped into the child's mouth every 6 months), albendazole (400 mg tablet every 6 months), both, or neither (open control). Analyses of retinol effects are by block (36 vs 36 clusters). The study spanned 5 calendar years, with 11 6-monthly mass-treatment days for all children then aged 6-72 months. Annually, one centre per block was randomly selected and visited by a study team 1-5 months after any trial vitamin A to sample blood (for retinol assay, technically reliable only after mid-study), examine eyes, and interview caregivers. Separately, all 8338 centres were visited every 6 months to monitor pre-school deaths (100,000 visits, 25,000 deaths at ages 1·0-6·0 years [the primary outcome]). This trial is registered at ClinicalTrials.gov, NCT00222547.. Estimated compliance with 6-monthly retinol supplements was 86%. Among 2581 versus 2584 children surveyed during the second half of the study, mean plasma retinol was one-sixth higher (0·72 [SE 0·01] vs 0·62 [0·01] μmol/L, increase 0·10 [SE 0·01] μmol/L) and the prevalence of severe deficiency was halved (retinol <0·35 μmol/L 6%vs 13%, decrease 7% [SE 1%]), as was that of Bitot's spots (1·4%vs 3·5%, decrease 2·1% [SE 0·7%]). Comparing the 36 retinol-allocated versus 36 control blocks in analyses of the primary outcome, deaths per child-care centre at ages 1·0-6·0 years during the 5-year study were 3·01 retinol versus 3·15 control (absolute reduction 0·14 [SE 0·11], mortality ratio 0·96, 95% CI 0·89-1·03, p=0·22), suggesting absolute risks of death between ages 1·0 and 6·0 years of approximately 2·5% retinol versus 2·6% control. No specific cause of death was significantly affected.. DEVTA contradicts the expectation from other trials that vitamin A supplementation would reduce child mortality by 20-30%, but cannot rule out some more modest effect. Meta-analysis of DEVTA plus eight previous randomised trials of supplementation (in various different populations) yielded a weighted average mortality reduction of 11% (95% CI 5-16, p=0·00015), reliably contradicting the hypothesis of no effect.. UK Medical Research Council, USAID, World Bank (vitamin A donated by Roche).

Topics: Adjuvants, Immunologic; Albendazole; Antiprotozoal Agents; Child; Child Mortality; Child, Preschool; Cluster Analysis; Dietary Supplements; Diterpenes; Female; Follow-Up Studies; Humans; India; Infant; Male; Retinyl Esters; Rural Health; Treatment Outcome; Vitamin A; Vitamin A Deficiency

A survey indicated that high-dose vitamin A (HD-VA) supplements had no apparent effect on vitamin A (VA) status, assessed by serum retinol concentrations, of Zambian children lt 5 y of age. To explore possible reasons for the lack of response, we quantified absorption, retention, and urinary elimination of either a single HD-VA supplement (209.8 micromol; 60 mg) or a smaller dose of stable isotope (SI)-labeled VA (17.5 micromol; 5 mg), which was used to estimate VA pool size, in 3- to 4-y-old Zambian boys (n = 4 for each VA dose). A tracer dose of [(14)C(2)]-labeled VA (0.925 kBq; 25 nCi) was coadministered with the HD-VA supplement or SI-labeled VA, and 24-h stool and urine samples were collected for 3 and 7 consecutive days, respectively, and 24-h urine samples at 4 later time points. Accelerator MS was used to quantify (14)C in stool and urine. Estimates of absorption, retention, and the urinary elimination rate (UER) were 83.8 +/- 7.1%, 76.3 +/- 6.7%, and 1.9 +/- 0.6%/d, respectively, for the HD-VA supplement and 76.5 +/- 9.5%, 71.1 +/- 9.4%, and 1.8 +/- 1.2%/d, respectively, for the SI-labeled VA. Mean estimates of absorption, retention, and the UER did not differ by size of the VA dose administered. Estimated absorption and retention were negatively associated with reported fever (r = minus 0.83; P = 0.011). The HD-VA supplement and SI-labeled VA were adequately absorbed, retained, and utilized in apparently healthy Zambian preschool-age boys; absorption and retention may be affected by recent fever.

Topics: Child, Preschool; Dietary Supplements; Diterpenes; Humans; Male; Mass Spectrometry; Particle Accelerators; Retinyl Esters; Vitamin A; Vitamin A Deficiency; Vitamins; Zambia

Genetically engineered "Golden Rice" contains up to 35 microg beta-carotene per gram of rice. It is important to determine the vitamin A equivalency of Golden Rice beta-carotene to project the potential effect of this biofortified grain in rice-consuming populations that commonly exhibit low vitamin A status.. The objective was to determine the vitamin A value of intrinsically labeled dietary Golden Rice in humans.. Golden Rice plants were grown hydroponically with heavy water (deuterium oxide) to generate deuterium-labeled [2H]beta-carotene in the rice grains. Golden Rice servings of 65-98 g (130-200 g cooked rice) containing 0.99-1.53 mg beta-carotene were fed to 5 healthy adult volunteers (3 women and 2 men) with 10 g butter. A reference dose of [13C10]retinyl acetate (0.4-1.0 mg) in oil was given to each volunteer 1 wk before ingestion of the Golden Rice dose. Blood samples were collected over 36 d.. Our results showed that the mean (+/-SD) area under the curve for the total serum response to [2H]retinol was 39.9 +/- 20.7 microg x d after the Golden Rice dose. Compared with that of the [13C10]retinyl acetate reference dose (84.7 +/- 34.6 microg x d), Golden Rice beta-carotene provided 0.24-0.94 mg retinol. Thus, the conversion factor of Golden Rice beta-carotene to retinol is 3.8 +/- 1.7 to 1 with a range of 1.9-6.4 to 1 by weight, or 2.0 +/- 0.9 to 1 with a range of 1.0-3.4 to 1 by moles.. Beta-carotene derived from Golden Rice is effectively converted to vitamin A in humans. This trial was registered at clinicaltrials.gov as NCT00680355.

Topics: Adult; Aged; Area Under Curve; beta Carotene; Diterpenes; Female; Humans; Male; Middle Aged; Oryza; Plants, Genetically Modified; Reference Values; Retinyl Esters; Vitamin A; Vitamin A Deficiency; Vitamins

The retinol isotope dilution (RID) method has been used to evaluate vitamin A (VA) status in healthy adults and children in low- and middle-income countries (LMIC) and to assess the efficacy of various VA interventions.. The study was designed to examine whether dried serum spots (DSS) can be applied to RID when conducting VA total body store (TBS) assessments in community settings.. Four days after an oral dose of 0.4 mg [13C10]retinyl acetate was administered to Filipino children (12-18 mo), a single blood draw was divided to isolate both serum and plasma. Serum (40 μL) was spotted and dried on Whatman 903 cards and shipped at ambient temperature whereas liquid plasma (LP) was frozen at -80°C and shipped on dry ice. The VA tracer to tracee ratio from DSS and LP was quantified by LC-MS/MS. Comparisons between DSS and LP paired samples (n = 72) were made for [13C10]retinol specific activity (SAp) by Pearson's correlation and for VA TBS by Bland-Altman analysis.. The sum of 3 coextracted DSS were required to consistently detect [13C10]retinol above the LC-MS/MS limit of quantitation (LOQ). [13C10]retinol SAp from DSS was highly correlated with SAp from LP (r = 0.945; P < 0.01). A comparison of methods for TBS determination using Bland-Altman analysis indicated agreement with an intraindividual difference of 24.7 μmol (4.6%). Mean total liver reserve (TLR) values from DSS and LP were 1.7 μmol/g (± 0.6 SD) and 1.6 μmol/g (± 0.6 SD), respectively.. VA TBS can be determined from DSS thereby reducing the logistics and cost of maintaining a cold chain by shipping samples at ambient temperature and, thus, making the RID technique more feasible in LMIC community settings. This trial was registered at https://clinicaltrials.gov as NCT03030339.

Topics: Chromatography, Liquid; Developing Countries; Diterpenes; Female; Humans; Indicator Dilution Techniques; Infant; Isotopes; Liver; Male; Nutrition Assessment; Nutritional Status; Philippines; Plasma; Refrigeration; Reproducibility of Results; Retinyl Esters; Serum; Tandem Mass Spectrometry; Temperature; Vitamin A; Vitamin A Deficiency

Topics: Administration, Oral; Burkina Faso; Carbon Isotopes; Child; Diterpenes; Humans; Liver; Radioisotope Dilution Technique; Retinyl Esters; Time Factors; Vitamin A; Vitamin A Deficiency

Retinol isotope dilution (RID) indirectly estimates vitamin A (VA) status. Multicompartment modeling of RID data is used to refine study designs and equations to calculate VA stores. Previous studies suggest that VA in slowly turning over pools is not traced if follow-up is not long enough; however, shorter RID studies are being investigated. Few long-term models have been published.. We determined the effect of time on mathematical models of VA kinetics, model parameters, and outcomes.. In this longitudinal study, women (mean ± SD age: 22 ± 3 y; n = 7) were given 2.0 µmol [14,15]-13C2-retinyl acetate. Blood samples were staggered from 4 h to 152 d; the fraction of dose in serum was modeled with compartmental models. Four model-time categories were created: full models that used all data (median: 137 d; range 97-152 d) and truncated shorter studies of 14, 27, and 52 d (range: 42-62 d). Outcomes included number of compartments to adequately model serum data, kinetic parameters, total traced VA mass, and time-to-dose equilibration. To gain insight into longer follow-up, an additional participant was given 17.5 µmol 13C4-VA, and data were modeled as long as enrichment was above baseline (5 y).. Longer follow-up times affected kinetic parameters and outcomes. Compared with the 14-d models, long-term full models required an additional compartment for adequate fit (14.3% compared with 100%; P = 0.0056) and had longer [median (quartile 1, quartile 3)] whole-body half-life [15.0 d (10.5, 72.6 d) compared with 135 d (115, 199 d); P = 0.0006], time-to-dose equilibration [3.40 d (3.14, 6.75 d) compared with 18.9 d (11.2, 25.7 d); P < 0.0001], and total traced mass [166 µmol VA (162, 252 µmol VA) compared with 476 µmol VA (290, 752 µmol VA); P = 0.0031].. Extended RID sampling alters numerous mathematically modeled, time-dependent outcomes in women. Length of study should be considered when using mathematical models for calculating total-body VA stores or kinetic parameters related to VA turnover. This study is registered at www.clinicaltrials.gov as NCT03248700.

Topics: Adult; Carbon Isotopes; Diterpenes; Female; Humans; Indicator Dilution Techniques; Kinetics; Longitudinal Studies; Models, Biological; Models, Theoretical; Nutritional Status; Retinyl Esters; Time Factors; United States; Vitamin A; Vitamin A Deficiency; Young Adult

The aim of this study was to describe anthropometric, biochemical, co-morbidity, and vitamin A nutritional status in severely obese adolescents before and 30, 180, and 365 days after Roux-en-Y gastric bypass (RYGB).. Federal University of Rio de Janeiro, Rio de Janeiro, Brazil.. Sixty-four adolescents (15-19 years old) with a body mass index≥40 kg/m. Before surgery, 26.6% of the sample group experienced vitamin A deficiency (VAD). Serum retinol levels dropped significantly 30 days after surgery and then returned to basal levels. There was a significant increase in the prevalence of β-carotene deficiency and night blindness throughout the postsurgery period. A significant reduction in blood glucose, insulin resistance, lipid profile, and anthropometric parameters was observed.. The finding that oral daily supplementation with 5000 IU retinol acetate failed to reverse VAD and night blindness after RYGB is highly significant. We recommend assessment of VAD and night blindness in extremely obese adolescents before and after RYGB. We further recommend monitoring for an additional 180 days (for VAD) and 365 days (for night blindness) after surgery, with particular attention to daily supplementation needs.

Topics: Adolescent; Anthropometry; Blood Glucose; Cholesterol, LDL; Diterpenes; Epidemiologic Methods; Female; Gastric Bypass; Humans; Male; Medication Adherence; Obesity, Morbid; Pediatric Obesity; Retinyl Esters; Triglycerides; Vitamin A; Vitamin A Deficiency; Vitamins; Young Adult

The WHO estimates that 190 million preschool children have vitamin A deficiency (VAD). Serum retinol (SR) concentration is a common indicator of vitamin A (VA) status, but SR is homeostatically controlled and suppressed during inflammation, which may lead to misdiagnosis.. The sensitivity and specificity of SR compared with VA total liver reserves (TLRs) were evaluated for VAD in children from Thailand (n = 37) and Zambia (n = 128). SR was adjusted for inflammation in the Zambian children.. Each child was classified as VA-deficient or not based on cutoffs of <0.1 μmol VA/g liver with the use of retinol isotope dilution and <0.7 μmol/L for SR concentrations. Four categories of infection status in the Zambian children were based on elevated C-reactive protein (CRP) and α1-acid glycoprotein (AGP). Sensitivity and specificity were calculated with the use of unadjusted and inflammation marker-adjusted SR cutoffs.. VAD was 65% and 0% according to TLRs and SR, respectively, in Thai children and 0% and 17%, respectively, in Zambian children. No true positive VAD cases occurred; thus, sensitivity was 0% and indeterminable, respectively; specificity was 100% and 82.8%, respectively. CRP was elevated in 26.6% of Zambian children, whereas 97.7% had elevated AGP, categorizing them as having no infection (2.3%) or in early (26.6%) or late (58.6%) convalescence. With the use of marker-adjusted SR cutoffs of 0.6 μmol/L for late convalescence and 0.5 μmol/L for early convalescence, the adjusted prevalence of SR deficiency was 2.3%, increasing specificity to 97.3%.. No cases of VAD were identified by both TLRs and SR (true positives) in Thai or Zambian children. Specificity of SR to evaluate VAD was high, but additional research is needed to investigate sensitivity. Adjusting SR cutoffs for inflammation improved specificity by reducing false positives. SR as a VAD indicator may depend on infection rates, which should be taken into consideration. These studies were registered at clinicaltrials.gov as NCT01061307 (for Thailand) and NCT01814891 (for Zambia).

Topics: Algorithms; C-Reactive Protein; Carbon Isotopes; Child; Child Nutritional Physiological Phenomena; Child, Preschool; Diterpenes; Female; Humans; Indicator Dilution Techniques; Inflammation Mediators; Liver; Male; Nutritional Status; Orosomucoid; Prevalence; Retinyl Esters; Rural Health; Sensitivity and Specificity; Thailand; Vitamin A; Vitamin A Deficiency; Zambia

Provitamin A biofortification of staple crops may decrease the prevalence of vitamin A (VA) deficiency if widely adopted in target countries. To assess the impact of processing methods on the VA value of plant foods, the unique bioefficacies of cis-βC isomers (formed during cooking) compared with all-trans (at) β-carotene (βC) must be determined. The bioefficacies of 9-cis (9c)- and 13-cis (13c)-βC isomers were compared with those of the at-βC isomer and VA positive (VA+) and negative (VA - ) controls in VA-depleted Mongolian gerbils (Meriones unguiculatus) in two experimental studies (study 1, n 56; study 2, n 57). A 3- or 4-week depletion period was followed by a 3- or 4-week treatment period in which the groups received oral doses of the 9c-, 13c- or at-βC isomers in cottonseed oil (study 1, 15 nmol/d; study 2, 30 nmol/d). In study 1, the βC isomers did not maintain baseline liver VA stores in all groups (0.69 (SD 0.20) μmol/liver) except in the VA+group (0.56 (SD 0.10) μmol/liver) (P= 0.0026). The βC groups were similar to the VA+group, but the 9c- and 13c-βC groups did not differ from the VA - group (0.39 (SD 0.09) μmol/liver). In study 2, the βC isomers maintained baseline liver VA stores in all the βC groups (0.35 (SD 0.13) μmol/liver), and in the VA+group, the VA supplement (0.54 (SD 0.19) μmol/liver) exceeded the baseline VA status (0.38 (SD 0.15) μmol/liver) (P< 0.0001); however, the 9c-βC group did not differ from the VA - group (0.20 (SD 0.07) μmol/liver). In vivo isomerisation of βC was confirmed in both experimental studies. Lower VA bioconversion factor values were obtained for the cis-βC isomers in study 2 when compared with study 1, but higher values were obtained for the at-βC isomer. Dose and VA status clearly affect bioconversion factors. In conclusion, the cis-βC isomers yielded similar liver VA stores to the at-βC isomer in Mongolian gerbils, and liver VA stores of the 9c- and 13c-βC groups did not differ when the doses were provided at physiological levels over time in two studies.

Topics: Animals; beta Carotene; Biotransformation; Chromatography, High Pressure Liquid; Dietary Supplements; Disease Models, Animal; Diterpenes; Gerbillinae; Liver; Male; Molecular Structure; Retinyl Esters; Stereoisomerism; Vitamin A; Vitamin A Deficiency

Topics: Adjuvants, Immunologic; Albendazole; Anthelmintics; Dietary Supplements; Diterpenes; Feces; Female; Helminthiasis; Humans; Male; Retinyl Esters; Vitamin A; Vitamin A Deficiency

A strategy to reduce the incidence of vitamin A deficiency is to improve precursor bioavailability from meals. Since vitamin A precursors are fat-soluble, we noted that carotenoids are more easily absorbed from food if prepared in such a way that the food matrix containing provitamin A (β-carotene) is sufficiently fat rich. To quantify this effect, we have developed a stable isotope methodology. By regular watering with 2H-labelled water, we were able to produce several kg of intrinsically labelled carrots, with carotenoids labelled to 0.63 % excess 2H. These were divided into 100 g portions and fed to a small group of healthy subjects both raw and stir-fried. To normalise for inter-individual variation in absorption and subsequent metabolism, small quantities of extrinsically 13C-labelled β-carotene and 2H-labelled retinol acetate were also incorporated into the meal. After ingestion of the carrots, blood lipids were monitored for a period of 3 d in order to determine the kinetics of β-carotene and retinol. From kinetic data, it was estimated that the bioavailability of carrot-derived β-carotene compared with pure β-carotene was about 11 % for raw carrots, but 75 % when the carrots were stir-fried. Conversely, there was a slight reduction in the bioconversion to retinol from β-carotene when the latter was derived from the stir-fried meal compared with that from raw carrots. When these two factors are combined, the yield of retinol from the carotene in carrots was found to be enhanced by a factor of 6.5 by stir-frying.

Topics: Adult; Antioxidants; beta Carotene; Biological Availability; Carbon Isotopes; Carotenoids; Cooking; Daucus carota; Deuterium; Diterpenes; Female; Humans; Male; Middle Aged; Nutritive Value; Reproducibility of Results; Retinoids; Retinyl Esters; Time Factors; Vitamin A; Vitamin A Deficiency

Relationships between increased adiposity and fat-soluble vitamin storage and metabolism are poorly understood. To examine these associations, 6% or 21% dietary fat was fed to rats for 11 weeks and tissue vitamin A storage determined. Two levels of supplemental vitamin A were administered. At the end of the tenth week, 3,4-didehydroretinol (DR) was administered orally, and its kinetics were followed for 1 week in serum and tissues. Model-based compartmental analysis was applied to these data. Kidney total retinol (R) concentrations were elevated in rats fed 6% compared with 21% dietary fat (n = 24/group). The fractional transfer coefficient (FTC) describing the movement of tracer from plasma to extravascular stores was two times higher in the 6% compared with the 21% fat group. Consistent with the elevated renal R in 6% fat fed rats, there was a 2-fold increase in the FTC representing tracer distribution from plasma to kidney in the 6% compared with 21% fat group. Taken together with a fat main effect on renal vitamin A, our data support the evidence that faster turnover of kidney R may help set the mechanism governing vitamin A tissue distribution during deficiency. Rats fed 21% versus 6% dietary fat conserved hepatic R more efficiently.

Topics: Adipose Tissue; Adiposity; Animals; Body Weight; Dietary Fats; Diterpenes; Liver; Male; Models, Biological; Obesity; Rats; Rats, Sprague-Dawley; Retinoids; Retinyl Esters; Vitamin A; Vitamin A Deficiency

While studying Guerin's carcinoma development under conditions of different vitamin A provision in the period of tumor growth and before it appearance, it was established, that strengthened saturation of an organism with a tumor by vitamin A hyper doses can both stimulate and inhibit tumor progression. The effect depends on duration of vitamin A administration and on the level of preliminary provision of an organism with this vitamin. The hyper doses administration for 7 days on the normal vitamin A provision background and the normal doses administration to vitamin A-deficient animals which is especially expressed antitumor effect. The continuation of hyper doses administration to 14 days leads to rising of tumor sizes, especially expressed in vitamin A-deficient animals.

Topics: Animals; Antineoplastic Agents; Diterpenes; Dose-Response Relationship, Drug; Drug Resistance, Neoplasm; Female; Neoplasm Transplantation; Neoplasms, Experimental; Rats; Retinyl Esters; Vitamin A; Vitamin A Deficiency

The deuterated-retinol-dilution technique provides a quantitative estimate of total-body vitamin A (TBVA) stores in adults. To apply the technique to children, information on plasma retinol kinetics in this age group is needed.. We described the plasma retinol kinetics of an oral dose of [(2)H(4)]retinyl acetate in a population of Peruvian children (12-24 mo of age) in order to examine the relation between TBVA stores and individual plasma isotopic ratios 3 d after the dose and to estimate 1) the time required for the isotope dose to mix with endogenous vitamin A, 2) the fractional catabolic rate for retinol, and 3) TBVA stores.. An oral dose of [(2)H(4)]retinyl acetate (14 micromol retinol equivalents) was administered to children (n = 107) to construct a population-level kinetic curve of the plasma ratio of [(2)H(4)]retinol to retinol to estimate equilibration time and the fractional catabolic rate. TBVA stores were estimated by using a modification of the isotope dilution equation for adults.. The dose of [(2)H(4)]retinyl acetate fully mixed with endogenous vitamin A 8 d after the dose. The fractional catabolic rate was 0.022/d (95% CI: 0.014, 0.030/d). Mean (+/- SD) TBVA stores were estimated as 0.097 +/- 0.081 mmol (range: 0.016-0.392 mmol). Plasma ratios of [(2)H(4)]retinol to retinol 3 d after the dose were correlated with the inverse of estimated TBVA stores (r = -0.74, P < 0.0001).. Compared with previous results in adults, the equilibration time occurred earlier and the estimated system fractional catabolic rate was higher in this population of children. The modified isotope dilution equation provided estimates of hepatic vitamin A concentration that are similar to values reported in US children at autopsy.

Topics: Administration, Oral; C-Reactive Protein; Child, Preschool; Deuterium; Diterpenes; Female; Humans; Infant; Liver; Male; Metabolic Clearance Rate; Nutritional Status; Peru; Retinyl Esters; Vitamin A; Vitamin A Deficiency

Vitamin A assessment methods that indirectly determine liver reserves are still in development. The deuterated vitamin A assay has been successfully applied in several population groups, but large doses of vitamin A must be used and the gas chromatography/mass spectrometry analysis is not very sensitive. Therefore, 10,11,14,15-(13)C(4)-retinyl acetate was synthesized using a modified Wittig-Horner procedure. Thereafter, female Sprague-Dawley rats (n = 47) were fed a vitamin A-deficient diet and divided into three groups: low (L), moderate (M) and high (H) vitamin A. Groups L, M and H were supplemented with 35, 70 and 350 nmol of unlabeled retinyl acetate/d for 17 d. On d 18, three rats from each group were killed to determine baseline (13)C levels. Serum was prepared, and livers were collected and stored at -70 degrees C until analyzed with HPLC and gas chromatography/combustion/isotope ratio mass spectrometry. The remaining rats were supplemented with 52 nmol of (13)C(4)-retinyl acetate. Rats were killed on d 1, 2, 4 and 10. The calculated and measured values of total body reserves (TBR) of vitamin A were within 7% of each other overall, and the relationship was linear (r = 0.98, P < 0.0001). The calculated mean TBR were 0.49 +/- 0.03, 0.82 +/- 0.007 and 3.72 +/- 0.40 micromol, and the measured mean TBR were 0.50 +/- 0.045, 0.69 +/- 0.10 and 3.6 +/- 0.29 micromol for groups L, M and H, respectively. In contrast, serum retinol concentrations did not show a difference among the dietary groups: 1.32 +/- 0.14, 1.35 +/- 0.17 and 1.28 +/- 0.15 micromol/L for groups L, M and H, respectively (P = 0.25). In conclusion, this method offers more sensitivity than traditional methods and may be applicable to human vitamin A status assessment when TBR estimations are desired.

Topics: Adjuvants, Immunologic; Analysis of Variance; Animals; Chromatography, High Pressure Liquid; Diet; Diterpenes; Female; Gas Chromatography-Mass Spectrometry; Liver; Nutritional Status; Rats; Rats, Sprague-Dawley; Retinyl Esters; Vitamin A; Vitamin A Deficiency

The deuterated retinol dilution technique is an indirect method for quantitatively estimating total body stores of vitamin A by using the postequilibration plasma isotopic ratio [2H4]retinol:retinol and the prediction model described by Furr et al (Am J Clin Nutr 1989;49:713-6). Limited data are available on the time required for an oral dose of labeled vitamin A to mix with vitamin A body stores in human subjects. This article describes the plasma retinol kinetics of an oral dose of [2H4] retinyl acetate in 4 healthy adults (2 men and 2 women) and 1 healthy female child in the United States and in 4 Bangladeshi women. After an oral dose of [2H4]retinyl acetate was administered, plasma samples were collected at 6, 12, and 24 h postdose during the first day and at 15 time points during the subsequent 90-d period for measurement of plasma [2H4]retinol:retinol. The mean respective plasma isotopic ratios on day 20 for US and Bangladeshi subjects (0.02 +/- 0.02 and 0.17 +/- 0.12, P = 0.03) and estimated total body vitamin A reserves (1.03 +/- 0.45 and 0.10 +/- 0.11 mmol, P = 0.003) were significantly different. The fraction of dose in plasma was plotted against time, and biexponential equations were fit to the kinetic data by using the time points from 24 h through day 90. The mean equilibration time (time required for the fraction of dose in plasma to reach a plateau) for all subjects was 16.6 +/- 3.8 d (11-23 d). There was no difference in estimated equilibration time between the group of US and Bangladeshi adult subjects (17.5 +/- 4.4 and 16.3 +/- 3.9 d, respectively, P = 0.69). Thus, the size of hepatic vitamin A reserves does not appear to affect equilibration time within the range of values observed.

Topics: Adolescent; Deuterium; Diterpenes; Female; Humans; Kinetics; Male; Nutritional Status; Retinyl Esters; Vitamin A; Vitamin A Deficiency

Maintenance of rats on a vitamin A-deficient diet resulting in undetectable levels of plasma retinol and significant reductions in relative testes weight compared to age-matched controls leads to the loss of liver membrane-bound low affinity glucocorticoid binding site (LAGS) activity without any effects on the levels of constitutively expressed CYP3A2 protein. Subsequent daily administration of retinol acetate to vitamin A-deficient rats results in the re-expression of LAGS activity to control levels by 7 days. To determine any role for the LAGS in the modulation of CYP3A2 expression by glucocorticoids, a single dose of dexamethasone 21-phosphate was administered to vitamin A-deficient rats and vitamin A-deficient rats induced to re-express LAGS by daily retinol acetate treatment. Retinol acetate administration alone induces CYP3A2 protein to apparent maximal levels since dexamethasone 21-phosphate does not further increase the induction response. However, CYP3A2 remains inducible to dexamethasone 21-phosphate in vitamin A-deficient rats. These data suggest that vitamin A status affects the expression of LAGS and CYP3A2 but that glucocorticoids regulate the induction of CYP3A2 by a mechanism(s) independent of their interaction with the LAGS.

Topics: Animals; Binding Sites; Cytochrome P-450 Enzyme System; Dexamethasone; Diterpenes; Male; Microsomes, Liver; Rats; Rats, Sprague-Dawley; Retinyl Esters; Steroid Hydroxylases; Vitamin A; Vitamin A Deficiency

The effect of vitamin A deficiency and vitamin A replacement on spermatogenesis in golden hamsters was studied using a light microscope. Male golden hamsters were fed a vitamin A deficient (VAD) diet from 3 weeks of age. Hamsters with a VAD diet reached maximum body weight at about 13 weeks. After 17 weeks, the body weight of the hamsters began to decrease. When their body weight decreased to 70 g, only Sertoli cells, spermatogonia, and a few spermatocytes were present within the seminiferous tubules. Administering retinol acetate (vitamin A) combined with a conventional diet to the VAD hamsters induced a reinitiation of spermatogenesis with stage-synchronization. At 9, 10, and 11 weeks after vitamin A replacement, the testes with active spermatogenesis possessed only a few successive stages of the seminiferous epithelial cycle.

Topics: Animals; Body Weight; Cell Cycle; Cricetinae; Diterpenes; Epithelium; Male; Mesocricetus; Reference Values; Retinyl Esters; Seminiferous Tubules; Sertoli Cells; Spermatocytes; Spermatogenesis; Spermatogonia; Vitamin A; Vitamin A Deficiency

Recently, we have reported that retinoic acid (RA), similarly to retinol acetate, is able to reinitiate spermatogenesis in vitamin A-deficient rats. Here, we investigated the expression of RA receptors RAR alpha, RAR beta, RAR gamma, and retinoid X receptor RXR alpha by Northern blot analysis of poly(A)+ RNA of testes of vitamin A-deficient rats before and after reinitiation of spermatogenesis induced by injection of retinol acetate or RA and testes of 21-day-old and 10-week-old normal rats. In the testis of vitamin A-deficient rats 1.9-, 2.8-, and 3.8-kilobase (kb) transcripts of RAR alpha; 2.8- and 3.3-kb transcripts of RAR beta; 1.8-, 2.8-, and 3.4-kb transcripts of RAR gamma; and two transcripts of RXR alpha of 2.5 and 4.8 kb are expressed. When vitamin A-deficient rats receive RA or retinol acetate, a 3-fold increase in the amount of poly(A)+ RNA per testis can be observed after 8 h, while the amounts of glyceraldehyde-3-phosphate dehydrogenase and sulfated glycoprotein-1 mRNA hardly change. Also, the expression of several transcripts of each RAR type is significantly increased from 1.8- up to 3.6-fold. Moreover, additional transcripts of RAR beta and RXR alpha (1.8 and 1.0 kb, respectively) can be detected. In the testes of 21-day-old rats, three transcripts of each RAR type and two RXR alpha transcripts are expressed. In contrast, in the normal adult rat testis the expression of all RARs, if present, is lower than that in the 21-day-old rat testis or the adult vitamin A-deficient rat testis. The expression of all transcripts of each RAR in the testis of 21-day-old rats shows great similarity with the expression in the testis of the vitamin A-deficient rat after replacement of retinol acetate or RA. These changes in expression indicate that RARs and RXR alpha may play a role in the process of proliferation and differentiation of A spermatogonia, which is induced in vitamin A-deficient rats shortly after replacement of RA or retinol acetate.

Topics: Animals; Blotting, Northern; Carrier Proteins; Diterpenes; Gene Expression; Male; Rats; Rats, Inbred Strains; Receptors, Retinoic Acid; Retinoids; Retinyl Esters; RNA, Messenger; Spermatogenesis; Testis; Transcription, Genetic; Tretinoin; Vitamin A; Vitamin A Deficiency

Vitamin A-deficient (A-) mice produce poor IgG antibody responses due to a helper T cell dysfunction. We performed retinoid repletion studies to determine the minimum dietary retinyl acetate dose and the most active retinoid for supporting immune function. Dietary retinyl acetate repletion at 2 (R2 group) or 4 (R4 group) microgram/g diet restored serum retinol in A- mice to vitamin A-sufficient (A+) control levels within 24 h. However, in R4 mice, liver retinyl palmitate was restored about twofold faster than in R2 mice; liver retinyl palmitate reached A+ control levels by d 30 in R4 mice but not in R2 mice. We challenged the mice with antigen 24 h post repletion; the R4 mice gave an IgG1 response equal to that of A+ controls, but the R2 mice were comparable with the A- controls. We also compared four retinoids for IgG1 response restoration in vitro; 1 nmol/L retinoic acid fully repleted A- cell IgG1 responses and helper T cell frequencies to the unsupplemented A+ control levels. Retinoic acid was at least 10-fold more active than retinyl acetate or retinaldehyde, and 100-fold more active than retinol. Collectively, our results suggest that retinoic acid is probably the physiologically important metabolite for sustaining IgG immune responses in vivo. We discuss the possible relationship between liver retinyl palmitate levels and availability of retinoic acid to support immune function.

Topics: Animals; Antibody Formation; B-Lymphocytes; Cells, Cultured; Diet; Diterpenes; Female; Immunoglobulin G; Male; Mice; Retinyl Esters; T-Lymphocytes; Tretinoin; Vitamin A; Vitamin A Deficiency

Topics: Animals; Chromatography, High Pressure Liquid; Diterpenes; Mathematics; Models, Theoretical; Radioisotope Dilution Technique; Rats; Retinol-Binding Proteins; Retinyl Esters; Tritium; Vitamin A; Vitamin A Deficiency

Short-term parenteral application of vitamin A was examined in rats. Retinyl margarinate, which is chemically similar to physiological retinyl esters, was used in vitamin A-depleted rats to study uptake, distribution, and storage of retinyl esters in tissues. Vitamin A-depleted and Vitamin A-sufficient rats were infused with a micellar suspension of retinyl margarinate for 7 h and then killed at different times. Retinyl margarinate was directly taken up by all tissues examined. It appears that infusion of retinyl esters in micellar form provides a direct way to supply vitamin A to peripheral, vitamin A-dependent tissues. Therefore, a short-term infusion of retinyl esters with an emulsifier may be an effective means of preventing development of vitamin A-deficiency during long-term application of TPN, particularly in cases of liver dysfunction.

Topics: Animals; Chromatography; Chromatography, High Pressure Liquid; Diterpenes; Intestinal Mucosa; Liver; Lung; Male; Parenteral Nutrition, Total; Rats; Retinyl Esters; Spleen; Testis; Tissue Distribution; Trachea; Vitamin A; Vitamin A Deficiency

Many tissues which require vitamin A store the vitamin as long-chain fatty acyl esters of retinol. As part of a study designed to characterize vitamin A metabolism in the lacrimal gland, which transports retinol from blood to lacrimal gland fluid, extracts from lacrimal glands of rabbits and rats were analyzed by non-aqueous high performance liquid chromatography. Retinyl linoleate, retinyl palmitate, and retinyl stearate were identified in these extracts by their co-elution with standards, their retention time relative to retinyl palmitate, and their susceptibility to hydrolysis by saponification. Retinyl palmitate was present in rabbit lacrimal gland at 51.0 +/- 10.1 ng/g tissue. After treatment of vitamin A-deficient rabbits with orally administered [11,12-3H] retinyl acetate, the radiolabeled esters retinyl linoleate, palmitate, and stearate were extracted from the lacrimal glands. These data show that the lacrimal gland stores vitamin A as fatty acyl esters of retinol.

Topics: Animals; Chromatography, High Pressure Liquid; Diterpenes; Lacrimal Apparatus; Rabbits; Retinoids; Retinyl Esters; Vitamin A; Vitamin A Deficiency

Post-mortem concentrations of hepatic retinol and retinyl esters were determined in 40 subjects aged over 65 years to assess the effects of disease and malnutrition on vitamin A reserves. Three groups of patients (mean age 79.6 years) were studied: (1) previously healthy, (2) chronically ill, (3) chronically ill and wasted. There was no significant difference in height or age between the groups, but group 3 was lighter than both group 1 (P less than 0.001) and group 2 (P less than 0.05). Free retinol and retinyl esters were measured by high pressure liquid chromatography, and the total hepatic retinol calculated. Analysis of variance showed that the three groups differed significantly (P less than 0.02) with regard to total retinol, retinyl palmitate and total retinyl ester content.

Topics: Aged; Aged, 80 and over; Animals; Autopsy; Chromatography, High Pressure Liquid; Chronic Disease; Diterpenes; Female; Humans; Liver; Male; Nutrition Disorders; Retinoids; Retinyl Esters; Vitamin A; Vitamin A Deficiency

Mice fed a semipurified, vitamin A-deficient diet (A- mice) and control animals fed the same diet with added retinyl acetate (A+ mice) were used to investigate the effect of vitamin A deficiency on primary immunoglobulin responses to protein antigens. At age 6 weeks, A- mice had serum retinol concentrations that were 46% of A+ controls. When immunized with a single antigen dose, these mice produced an antigen-specific IgM response equivalent to controls, but their IgG1 and IgG3 responses were sharply diminished (less than 30% of A+ controls). At age 8 weeks, A- mice had 20% of A+ serum retinol concentrations and less than 17% of A+ liver retinyl palmitate levels. Responding to a single antigen dose, A- mice produced approximately equal to 70% as much IgM as A+ controls. Their IgG1 response was less than 30% and their IgG3 response less than 3% of A+ controls. The IgG1 response kinetics were identical in A- and A+ mice. Diminished serum antibody responses in A- mice were attributable to fewer immunoglobulin-secreting plasma cells rather than to a decline in IgM or IgG secretion rate per cell. Total serum IgG3 levels, irrespective of antigen specificity, were slightly elevated in A- mice compared to A+ controls. The inefficient clonal expansion of responding B lymphocytes and contrasting impairment of IgM and IgG responses observed in vitamin A-deficient mice are discussed with respect to a possible helper/inducer-T-lymphocyte defect.

Topics: Animals; Antibody Formation; Body Weight; Diterpenes; Hemocyanins; Immunoglobulin G; Immunoglobulin M; Kinetics; Mice; Muramidase; Retinyl Esters; Vitamin A; Vitamin A Deficiency

It was demonstrated that the development of experimental avitaminosis A in chicks led to secondary zinc deficiency. The balance of Zn in the chick became negative, while the Zn content of various tissues decreased. Thus in vitamin-A-deficient chicks the serum Zn content was 1258 (SD 26.3) micrograms/l which was considerably lower than 1652 (SD 97.8) micrograms/l in controls. Zn absorption was considerably reduced throughout the entire small intestine of vitamin-A-deficient chicks and most markedly in the ileal region. Within 72 h after retinyl acetate administration Zn absorption was fully restored in this region of the intestine. The 65Zn-binding capacity of soluble proteins, present in the supernatant fraction of ileal-mucosa homogenates of vitamin-A-deficient chicks, was found to increase 2.6 times by 72 h after the administration of a single dose of retinyl acetate. A vitamin-A-dependent Zn-binding protein (ZnBP), absent in vitamin-A-deficient chicks, was isolated from the ileal mucosa after their repletion with vitamin A. Competitive-binding studies (calcium, cadmium, copper) showed the protein to be highly specific for Zn ions. The molecular weight of ZnBP was 83 kDa. The association constant of the protein-Zn complex was 0.8 X 10(6)/mol. The protein was acidic with approximately 20% of its amino acid residues belonging to dicarboxylic acids. ZnBP was found to be a glycoprotein, and it contained hexose as a carbohydrate component. It is suggested that ZnBP is involved in the binding of Zn in the ileal mucosa of chicks.

Topics: Animals; Chickens; Diterpenes; Intestinal Absorption; Intestine, Small; Male; Proteins; Retinyl Esters; Vitamin A; Vitamin A Deficiency; Zinc

The acetate and palmitate esters of 3,4-didehydroretinol (DR; vitamin A2 alcohol) have been synthesized and characterized. When administered orally in corn oil to female rats, DR was present in the serum as the alcohol, but primarily as esters in the liver. As total stores of retinol (R; vitamin A1 alcohol) decrease, the ratio of DR to R in the serum markedly increases. The ratio of DR to R in serum was greater than 0.27 at liver vitamin A1 palmitate values of less than 3 micrograms/g, 0.05-0.14 at 3-19 micrograms/g, and less than 0.04 at greater than or equal to 20 micrograms/g. Thus, the ratio of DR to R in the serum at a suitable interval after the administration of dehydroretinyl acetate may aid in assessing marginal vitamin A status. DR was not demonstrably converted to R in these studies.

Topics: Animals; Diterpenes; Female; Liver; Rats; Rats, Inbred Strains; Retinyl Esters; Vitamin A; Vitamin A Deficiency

Earlier work from our laboratory had shown that vitamin A-deficient rats had increased levels of fibronectin in their serum. To explain this result, we investigated the mechanism whereby vitamin A deficiency affects the production of fibronectin by liver and hepatocytes, since liver is the known source of plasma fibronectin. By use of cDNA specific for rat liver fibronectin, we showed that livers of vitamin A-deficient rats had a 2-4-fold increase in the level of fibronectin mRNA and also a higher transcription rate. Rate of synthesis and secretion of fibronectin was found to be increased 2-fold in primary cultures of hepatocytes of deficient animals. Exogenous addition of retinyl acetate or retinoic acid to the media reversed this increase to control levels. The increase was paralleled by an increase in fibronectin mRNA, also reversed by exogenous retinoic acid. At least 12 h were needed for this reversal to take place. Thus, vitamin A appears to regulate the synthesis of fibronectin through its action on fibronectin mRNA transcription. This represents the first reported observation of an action of vitamin A at the genomic level on the synthesis of a specific protein in liver.

Topics: Animals; Cells, Cultured; Diterpenes; Fibronectins; Gene Expression Regulation; Kinetics; Liver; Male; Rats; Retinyl Esters; RNA, Messenger; Transcription, Genetic; Tretinoin; Vitamin A; Vitamin A Deficiency

Tracheas from vitamin A-deficient hamsters in organ culture in vitamin A-free medium developed squamous metaplasia. Addition of retinyl acetate to the medium prevented squamous metaplasia and a mucociliary epithelium was maintained. Indirect immunofluorescent staining with antikeratin antibodies AE1 and AE3 indicated positive reactions with epithelium of tracheas either cultured in vitamin A-free or retinyl acetate (RAc)-containing medium. The "stratum corneum"-like squames in metaplastic tracheas were strongly stained by AE3. Immunoprecipitation of cytoskeletal extracts from [35S]methionine labeled tracheas with a multivalent keratin antiserum indicated that the concentration of keratins synthesized in tracheas cultured in vitamin A-free medium was greater than that observed in tracheas cultured in the presence of RAc. In addition, new species of keratin were expressed in tracheas cultured in RAc-free medium. Alterations in the program of keratin synthesis were clearly detectable after 1 d in vitamin A-free medium, even though squamous metaplasia was not yet obvious. Squamous tracheas were shown by immunoblot analysis to contain keratins of 50, 48, 46.5, and 45 kilodalton (kd) detected with AE1; and 58, 56, and 52 kd detected with AE3. Immunoblot analysis with monospecific antimouse keratin sera also demonstrated the presence of 60, 55, and 50 kd keratins in the metaplastic tracheas. All these various species of keratins were either absent or present in much reduced quantity in mucociliary tracheas in RAc-containing medium. Interestingly, the induction of squamous metaplasia in tracheal epithelium did not result in the expression of the 59 and 67 kd keratins which are characteristically expressed in the differentiated layers of the epidermis. Therefore, this study shows that squamous metaplasia of tracheas due to vitamin A-free cultivation is accompanied by an increase in keratin synthesis as well as by the appearance of keratin species not normally present in mucociliary tracheal epithelium.

Topics: Animals; Cricetinae; Cytoskeleton; Diterpenes; Electrophoresis, Polyacrylamide Gel; Epithelium; Fluorescent Antibody Technique; Immunologic Techniques; Immunosorbent Techniques; Keratins; Mesocricetus; Metaplasia; Organ Culture Techniques; Retinyl Esters; Trachea; Vitamin A; Vitamin A Deficiency

We have examined RNA synthesis by nuclei isolated from testes of rats of varying vitamin A status. Nuclei from retinol-deficient animals showed substantially decreased RNA synthesis by polymerase II when compared to nuclei from normal animals. Within 4 hours after oral administration of retinyl acetate (as the source of retinol) to deficient animals, RNA synthesis by polymerase II had significantly increased. Administration of retinoic acid had a similar but lesser effect. Nucleoside analysis after alkaline hydrolysis of the RNA synthesized by the endogenous polymerase II suggested that the increased activity was due to a greater number of actively transcribing polymerase II molecules on the DNA. Further, when the template capacity of testicular chromatin isolated from deficient and retinyl acetate refed animals was compared, the number of sites recognized by E. coli RNA polymerase was increased twofold after retinyl acetate administration. We conclude that these retinol-induced changes in transcription are due at least in part to changes in chromatin structure.

Topics: Animals; Chromatin; Diterpenes; Male; Rats; Retinyl Esters; RNA; RNA Polymerase II; Testis; Transcription, Genetic; Tretinoin; Vitamin A; Vitamin A Deficiency

The effects of severe vitamin A deficiency (liver retinol less than 2 micrograms/g) on hepatic folate metabolism in rats were studied. The oxidation of a [ring-2-14C] histidine load or a [14C]formate load to 14CO2 was significantly depressed in vitamin A-deficient rats and those given histidine also excreted more urinary formiminoglutamic acid (FiGlu) than pair-fed controls. The increase in FiGlu excretion was not due to augmented production from histidine, implicating an impairment of FiGlu catabolism. FiGlu formiminotransferase activity was unaltered in vitamin A-deficient rats, but hepatic tetrahydrofolic acid (THF) concentration was decreased by 58% in vitamin A-deficient rats given a histidine load while 5-methyl-THF concentration was increased by 39%. Formyl-THF and total folate levels were similar to controls. A redistribution of folate coenzymes was not found in vitamin A-deficient rats not force fed histidine. A 43% decrease in 10-formyl-THF dehydrogenase activity, which generates both THF and the 14CO2 from the labeled substrates, and an 81% increase in 5,10-methylene-THF reductase activity, which generates 5-methyl-THF, were found in vitamin A-deficient rats. It appears that the production of severe vitamin A deficiency results in selective changes in the activities of hepatic folate-dependent enzymes, so that when a load of a one-carbon donor is given, THF concentration decreases and metabolism of the load is impaired.

Topics: Animals; Diterpenes; Folic Acid; Formiminoglutamic Acid; Histidine; Histidine Ammonia-Lyase; Liver; Male; Rats; Rats, Inbred Strains; Retinyl Esters; S-Adenosylhomocysteine; S-Adenosylmethionine; Urocanate Hydratase; Vitamin A; Vitamin A Deficiency

The uptake and chemical identification of 14C-retinyl acetate in the inner ear of the guinea-pig after oral administration is reported. For methodological reasons the experiment was carried out in vitamin A-deficient guinea-pigs. In the sensory tissues a time-dependent distribution was found similar to that in other organs. The chemical identification shows that the orally administered labeled retinyl acetate can be detected as retinyl palmitate in the membranous structures of the inner ear. This may be an indication for the ability of the inner ear tissues to esterize and probably store the transport form of vitamin A, retinol.

Topics: Administration, Oral; Animals; Autoradiography; Brain; Diterpenes; Ear, Inner; Guinea Pigs; Kidney; Liver; Lung; Male; Myocardium; Olfactory Mucosa; Retinyl Esters; Sensory Receptor Cells; Spleen; Testis; Vitamin A; Vitamin A Deficiency

Topics: Animals; Carbon Radioisotopes; Chromatography, High Pressure Liquid; Diterpenes; Ear, Inner; Guinea Pigs; Humans; Male; Olfactory Bulb; Pineal Gland; Rats; Rats, Inbred Strains; Retinyl Esters; Vitamin A; Vitamin A Deficiency

The kinetics and metabolism of physiological doses of all-trans-retinoic acid were examined in blood and small intestinal mucosa of vitamin A-depleted rats. A major portion of intrajugularly injected retinoic acid is rapidly (within 2 min) sequestered by tissues; subsequently 13-cis-retinoic acid and polar metabolites are released into circulation. All-trans-retinoic acid appears in small intestinal epithelium within 2 min after dosing and is the major radioactive compound there for at least 2 h. Retinoyl glucuronide and 13-cis-retinoic acid are early metabolites of all-trans-retinoic acid in the small intestine of bile duct-cannulated rats. Retinoyl glucuronide, the major metabolite of retinoic acid intestinal epithelium, in contrast to other polar metabolites, was not detected in circulation. An examination of [3H]retinyl acetate metabolites under steady state conditions in vitamin A-repleted rats demonstrates the occurrence of all-trans-retinoic acid and 13-cis-retinoic acid in circulation and in intestinal epithelium, in a pattern similar to that found after injection of retinoic acid into vitamin A-depleted rats. Our data establish that all-trans-retinoic acid, 13-cis-retinoic acid, and retinoyl glucuronide are physiological metabolites of vitamin A in target tissues, and therefore are important candidates as mediators of the biological effect of the vitamin.

Topics: Animals; Chromatography, High Pressure Liquid; Diterpenes; Intestinal Mucosa; Intestine, Small; Isomerism; Kinetics; Male; Rats; Rats, Inbred Strains; Retinoids; Retinyl Esters; Structure-Activity Relationship; Tretinoin; Tritium; Vitamin A; Vitamin A Deficiency

Male Sprague-Dawley rats were maintained on a vitamin A-deficient diet for a period of five weeks. At the end of that time, hepatic cytochrome P450 levels in vitamin A-deficient rats were 65% that of rats fed a complete diet. However, the hepatic rate of benzo[a]pyrene metabolism was significantly greater (2 times) in vitamin A-deficient rats compared with those fed a complete diet. The pattern of metabolites separable by thin-layer chromatography was similar in both groups of rats. Benzo[a]pyrene induced its own metabolism by a slightly greater amount in the vitamin-sufficient rats, but it was not to the level of the deficient group, although the levels of cytochrome P450 were still below those of the deficient rats. In discussing lung microsomes, benzo[a]pyrene pre-treatment of deficient rats resulted in slightly elevated levels of cytochrome P450 and a slightly greater rate of metabolism of benzo[a]pyrene compared with rats fed the complete diet.

Topics: Animals; Benzo(a)pyrene; Cytochrome P-450 Enzyme System; Diterpenes; Enzyme Induction; Inactivation, Metabolic; Liver; Lung; Male; Microsomes, Liver; Rats; Rats, Inbred Strains; Retinyl Esters; Vitamin A; Vitamin A Deficiency

Following intratesticular injection, the metabolism of all-trans-[11-3H] retinyl acetate was studied in rats fed a vitamin A-deficient diet supplemented either with retinyl palmitate (-A + RP) or retinoic acid (-A + RA). Analysis of testicular metabolites by HPLC at 6 h and 24 h demonstrated the hydrolysis of retinyl acetate to retinol, esterification of retinol to retinyl palmitate and the formation of trace amounts of retinoic acid and other metabolites in both groups of rats. Eight and nine metabolite peaks were present in the -A + RP and -A + RA groups, respectively. The HPLC profile was similar in both groups of rats but the amounts of metabolites differed.

Topics: Animals; Chromatography, High Pressure Liquid; Diterpenes; Isomerism; Kinetics; Male; Rats; Rats, Inbred Strains; Retinyl Esters; Testis; Tritium; Vitamin A; Vitamin A Deficiency

A number of recent studies have indicated that the expression of keratins is altered upon malignant transformation of human epithelial cells. We have shown that the altered expression of 67-kDa and 40-kDa keratins in established squamous cell carcinoma lines from tongue and epidermis stems largely from a difference in their sensitivity to vitamin A apparently acquired during tumorigenesis. When the vitamin A concentration in the medium is raised, the 40-kDa keratin is produced at increased levels. Conversely, when the amount of vitamin is reduced, the 67-kDa keratin is synthesized and the cells undergo stratification and terminal differentiation. However, even when vitamin A is quantitatively removed from the medium, the maximal degree of differentiation attained by each squamous cell carcinoma cell as judged by the synthesis of 67-kDa keratin was still less than that of the normal keratinocytes. These findings suggest that the altered patterns of keratins observed for some tissues upon malignant transformation arise from a complex mixture of intracellular changes in the differentiative pathway in addition to changes in the responsiveness of cells to extracellular regulators of keratin gene expression.

Topics: Animals; Carcinoma, Squamous Cell; Carrier Proteins; Cell Differentiation; Cell Line; Diterpenes; Dose-Response Relationship, Drug; Epithelium; Fluorescent Antibody Technique; Humans; Infant, Newborn; Keratins; Male; Rabbits; Receptors, Retinoic Acid; Retinyl Esters; RNA, Messenger; Vitamin A; Vitamin A Deficiency

A study was conducted on the incorporation of [11-3H]retinyl acetate into various retinyl esters in liver tissues of rats either vitamin A-sufficient, vitamin A-deficient or vitamin A-deficient and maintained on retinoic acid. Further, the metabolism of [11-3H]retinyl acetate to polar metabolites in liver tissues of these three groups of animals was investigated. Retinol metabolites were analyzed by high-performance liquid chromatography. In vitamin A-sufficient rat liver, the incorporation of radioactivity into retinyl palmitate and stearate was observed at 0.25 h after the injection of the label. The label was further detected in retinyl laurate, myristate, palmitoleate, linoleate, pentadecanoate and heptadecanoate 3 h after the injection. The specific radioactivities (dpm/nmol) of all retinyl esters increased with time. However, the rate of increase in the specific radioactivity of retinyl laurate was found to be significantly higher (66-fold) than that of retinyl palmitate 24 h after the injection of the label. 7 days after the injection of the label, the specific radioactivity between different retinyl esters were found to be similar, indicating that newly dosed labelled vitamin A had now mixed uniformly with the endogenous pool of vitamin A in the liver. The esterification of labelled retinol was not detected in liver tissues of vitamin A-deficient or retinoic acid-supplemented rats at any of the time point studied. Among the polar metabolites analyzed, the formation of [3H]retinoic acid from [3H]retinyl acetate was found only in vitamin A-deficient rat liver 24 h after the injection of the label. A new polar metabolite of retinol (RM) was detected in liver of the three groups of animals. The formation of 3H-labelled metabolite RM from [3H]retinyl acetate was not detected until 7 days after the injection of the label in the vitamin A-sufficient rat liver, suggesting that metabolite RM could be derived from a more stable pool of vitamin A.

Topics: Animals; Chromatography, High Pressure Liquid; Diterpenes; Female; Kinetics; Liver; Male; Rats; Rats, Inbred Strains; Retinyl Esters; Tretinoin; Tritium; Vitamin A; Vitamin A Deficiency

Topics: Animals; Diterpenes; DNA; Genes; Intestinal Mucosa; Liver; Male; Poly A; Protein Biosynthesis; Rats; Rats, Inbred Strains; Retinyl Esters; RNA; RNA, Messenger; Testis; Transcription, Genetic; Tretinoin; Vitamin A; Vitamin A Deficiency

Syrian golden hamsters were placed on a control or vitamin A-deficient diet. When their serum vitamin A content was significantly reduced, i.e., to less than 10% of controls, the hamsters were killed and lung aryl hydrocarbon hydroxylase activity and metabolism of benzo(a)pyrene were determined. The benzo(a)pyrene metabolite profile was similar with control and A-deficient systems, and only few quantitative differences were noted. Addition of beta-retinyl acetate to the in vitro incubations did not substantially affect benzo(a)pyrene metabolism.

Topics: Animals; Aryl Hydrocarbon Hydroxylases; Benzopyrenes; Cricetinae; Diterpenes; In Vitro Techniques; Lung; Male; Mesocricetus; Microsomes; Retinyl Esters; Vitamin A; Vitamin A Deficiency

Biological properties of axerophthene, the hydrocarbon analog of retinol, have been studied both in vitro and in vivo. In tracheal organ culture axerophthene reversed keratinization caused by deficiency of retinoid in the culture medium; its potency was of the same order of magnitude as that of retinyl acetate. Axerophthene supported growth in hamsters fed vitamin A-deficient diets although less effectively than did retinyl acetate. Axerophthene was considerably less toxic than was retinyl acetate when administered repeatedly in high doses to rats. Administration of an equivalent p.o. dose of axerophthene caused much less deposition of retinyl palmitate in the liver than did the same dose of retinyl acetate, while a greater level of total retinoid was found in the mammary gland after administration of axerophthene.

Topics: Animals; Body Weight; Diterpenes; Female; Keratins; Liver; Mammary Glands, Animal; Mammary Neoplasms, Experimental; Organ Culture Techniques; Rats; Retinyl Esters; Trachea; Vitamin A; Vitamin A Deficiency

1. Oxidation of vitamin A acetate with monoperphthalic acid gave 5,6-monoepoxyvitamin A acetate, C(22)H(32)O(3), obtained as pale-yellow crystals, m.p. 65-66 degrees . 2. Saponification of 5,6-monoepoxyvitamin A acetate yielded 5,6-monoepoxyvitamin A alcohol, which was readily oxidized with manganese dioxide to 5,6-monoepoxyvitamin A aldehyde, obtained as yellow crystals, m.p. 101-102 degrees . It was the most stable of all the epoxy compounds studied. 3. Treatment of the 5,6-epoxy compounds with ethanolic hydrochloric acid gave the corresponding 5,8-epoxy (furanoid) compounds. 5,8-Monoepoxyvitamin A aldehyde was obtained as crystals, m.p. 104-105 degrees , but was very unstable. 4. Crystalline semicarbazones and phenylhydrazones with constant melting points and characteristic spectra were prepared from 5,6- and 5,8-monoepoxyvitamin A aldehyde. 5. Reduction of 5,6- and 5,8-monoepoxyvitamin A aldehyde with lithium aluminium hydride gave the corresponding 5,6- and 5,8-monoepoxyvitamin A alcohol. 6. 5,6- and 5,8-Monoepoxyvitamin A aldehyde were fed to vitamin A-deficient rats, and the compounds obtained from the livers of rats were indistinguishable from the reduction products obtained with lithium aluminium hydride. 7. The structures of the epoxy compounds were confirmed by their chromatographic behaviour, elemental analyses, ultraviolet-, visible- and infrared-absorption spectra and nuclear-magnetic-resonance spectra.

Topics: Acetates; Alcohols; Aldehydes; Biochemical Phenomena; Biochemistry; Chromatography; Diterpenes; Ethanol; Ethers; Ethers, Cyclic; Infrared Rays; Liver; Magnetic Resonance Imaging; Magnetic Resonance Spectroscopy; Rats; Research; Retinyl Esters; Spectrum Analysis; Ultraviolet Rays; Vitamin A; Vitamin A Deficiency

1. The metabolism of 5,6-monoepoxyvitamin A aldehyde in the rat was found to be identical with that of vitamin A aldehyde. It promptly alleviated all the symptoms of vitamin A deficiency and promoted the growth of the vitamin A-deficient rats. 2. When administered orally, 5,6-monoepoxyvitamin A aldehyde was reduced to the corresponding alcohol in the intestine and esterified before being transported to the liver for storage. 3. 5,6-Monoepoxyvitamin A aldehyde was not converted into the furanoid form, 5,8-monoepoxyvitamin A aldehyde, during passage through the stomach. 4. Intraperitoneal administration of 5,6-monoepoxyvitamin A aldehyde led to the accumulation of 5,6-monoepoxyvitamin A in the liver and other tissues. Subcutaneous administration of this compound alleviated all the symptoms of vitamin A deficiency. 5. The small intestine is the major, if not the only, site for the metabolic reduction of 5,6-monoepoxyvitamin A aldehyde and its subsequent esterification. 6. It was demonstrated that the rat possesses the necessary enzymes for the reduction and oxidation of 5,6-monoepoxyvitamin A aldehyde to the corresponding alcohol and acid as well as the esterification of 5,6-monoepoxyvitamin A alcohol to its palmitate. These metabolic conversions were shown to be as efficient as those of vitamin A aldehyde and alcohol. 7. 5,6-Monoepoxyvitamin A aldehyde possesses a biological potency 108% that of all-trans vitamin A acetate. 8. A new visual pigment with lambda(max.) 480mmu, along with natural rhodopsin, was isolated from the retinas of rats maintained on 5,6-monoepoxyvitamin A aldehyde. 9. Oral administration of 5,8-monoepoxyvitamin A aldehyde to vitamin A-deficient rats led to the accumulation of 5,8-monoepoxyvitamin A in the liver and other tissues. Enzymic reduction and oxidation of 5,8-monoepoxyvitamin A aldehyde to its alcohol and acid, as well as the esterification of the alcohol, were demonstrated.

Topics: Alcohols; Aldehydes; Chromatography; Diterpenes; Ethers; Ethers, Cyclic; Intestine, Small; Intestines; Liver; Metabolism; Rats; Research; Retina; Retinyl Esters; Stomach; Ultraviolet Rays; Vitamin A; Vitamin A Deficiency

Topics: Animals; Blood; Chromatography; Diet; Diterpenes; Liver; Meat; Metabolism; Poultry; Research; Retinyl Esters; Tocopherols; Vitamin A; Vitamin A Deficiency; Vitamin E