thyronines and Body-Weight

3-Iodothyronamine (3-T1 AM) is an endogenous thyroid hormone derivative reported to induce strong hypothermia and bradycardia within minutes upon injection in rodents. Although 3-T1 AM is rapidly converted to several other metabolites in vivo, these strong pharmacological responses were solely attributed to 3-T1 AM, leaving potential contributions of downstream products untested. We therefore examined the cardiometabolic effects of 3-iodothyroacetic acid (TA1 ), the main degradation product of 3-T1 AM.. We used a sensitive implantable radiotelemetry system in C57/Bl6J mice to study the effects of TA1 on body temperature and heart rate, as well as other metabolic parameters.. Interestingly, despite using pharmacological TA1 doses, we observed no effects on heart rate or body temperature after a single TA1 injection (50 mg·kg(-1) , i.p.) compared to sham-injected controls. Repeated administration of TA1 (5 mg·kg(-1) , i.p. for 7 days) likewise did not alter body weight, food and water intake, heart rate, blood pressure, brown adipose tissue (BAT) thermogenesis or body temperature. Moreover, mRNA expression of tissue specific genes in heart, kidney, liver, BAT and lung was also not altered by TA1 compared to sham-injected controls.. Our data therefore conclusively demonstrate that TA1 does not contribute to the cardiovascular or thermoregulatory effects observed after 3-T1 AM administration in mice, suggesting that the oxidative deamination constitutes an important deactivation mechanism for 3-T1 AM with possible implications for cardiovascular and thermoregulatory functions.

Topics: Adipose Tissue, Brown; Animals; Blood Pressure; Body Temperature; Body Weight; Eating; Heart Rate; Kidney; Liver; Lung; Male; Mice, Inbred C57BL; Myocardium; RNA, Messenger; Thyronines; Thyroxine; Transcriptome; Triiodothyronine

3-Iodothyronamine (T1 AM), an analog of thyroid hormone, is a recently discovered fast-acting endogenous metabolite. Single high-dose treatments of T1 AM have produced rapid short-term effects, including a reduction of body temperature, bradycardia, and hyperglycemia in mice.. The effect of daily low doses of T1 AM (10 mg/kg) for 8 days on weight loss and metabolism in spontaneously overweight mice was monitored. The experiments were repeated twice (n = 4). Nuclear magnetic resonance (NMR) spectroscopy of plasma and real-time analysis of exhaled (13) CO2 in breath by cavity ring down spectroscopy (CRDS) were used to detect T1 AM-induced lipolysis.. CRDS detected increased lipolysis in breath shortly after T1 AM administration that was associated with a significant weight loss but independent of food consumption. NMR spectroscopy revealed alterations in key metabolites in serum: valine, glycine, and 3-hydroxybutyrate, suggesting that the subchronic effects of T1 AM include both lipolysis and protein breakdown. After discontinuation of T1 AM treatment, mice regained only 1.8% of the lost weight in the following 2 weeks, indicating lasting effects of T1 AM on weight maintenance.. CRDS in combination with NMR and (13) C-metabolic tracing constitute a powerful method of investigation in obesity studies for identifying in vivo biochemical pathway shifts and unanticipated debilitating side effects.

Topics: 3-Hydroxybutyric Acid; Animals; Body Weight; Breath Tests; Dietary Proteins; Dose-Response Relationship, Drug; Female; Glycine; Lipolysis; Magnetic Resonance Spectroscopy; Metabolomics; Mice; Obesity; Thyronines; Valine; Weight Loss

Despite significant medical benefits as in space exploration or emergency care, prolonged torpidity of non-hibernator mammals remains unexplored to date. Here, we report that male Institute of Cancer Research mice could sustain two separate 2-day torpor bouts and maintain body temperature of 28-33°C following repeated treatments of 3-iodothyronamine (T(1) AM), a natural derivative of thyroid hormone. A 1-day interbout arousal period, adopted to mimic the behavior of true hibernators, seemed critical for the subjects to restore physiological homeostasis. Molecular studies of neuron-specific enolase, S100 calcium binding protein B and heat shock protein 72 suggested that the brain maintains functional and cytoprotective activities during sustained torpidity. Together, the results of this study propose a practical protocol using a torpor-arousal cycle that can be applied to the extreme medical situations.

Topics: Animals; Behavior, Animal; Body Temperature; Body Weight; Dose-Response Relationship, Drug; Hibernation; Male; Mice; Mice, Inbred ICR; Nervous System; Oxygen Consumption; Thyronines; Time Factors

Chronic overnutrition and modern lifestyles are causing a worldwide epidemic of obesity and associated comorbidities, which is creating a demand to identify underlying biological mechanisms and to devise effective treatments. In rats receiving a high-fat diet (HFD), we analyzed the effects of a 4-wk administration of a novel functional analog of iodothyronines, TRC150094 (TRC). HFD-TRC rats exhibited increased energy expenditure (+24% vs. HFD rats; P<0.05) and body weight (BW) gain comparable to that of standard chow-fed (N) rats [N, HFD, and HFD-TRC rats, +97 g, +140 g (P<0.05 vs. N), and +98 g (P<0.05 vs. HFD)]. HFD-TRC rats had significantly less visceral adipose tissue (vs. HFD rats) and exhibited altered metabolism in two major tissues that are very active metabolically. In liver, mitochondrial fatty acid import and oxidation were increased (+56 and +32%, respectively; P<0.05 vs. HFD rats), and consequently the hepatic triglyceride content was lower (-35%; P<0.05 vs. HFD rats). These effects were independent of the AMP-activated protein kinase-acetyl CoA-carboxylase-malonyl CoA pathway but involved sirtuin 1 activation. In skeletal muscle, TRC induced a fiber shift toward the oxidative type in tibialis anterior muscle, increasing its capacity to oxidize fatty acids. HFD-TRC rats had lower (vs. HFD rats) plasma cholesterol and triglyceride concentrations. If reproduced in humans, these results will open interesting possibilities regarding the counteraction of metabolic dysfunction associated with ectopic/visceral fat accumulation.

Topics: Adiposity; Animals; Blotting, Western; Body Weight; Carnitine O-Palmitoyltransferase; Dietary Fats; Eating; Energy Metabolism; Fatty Acids; Male; Obesity; Oxidation-Reduction; Rats; Rats, Wistar; Sirtuin 1; Thyronines; Thyrotropin; Thyroxine; Triglycerides; Triiodothyronine

The purpose of this study was to investigate the immediate and long-term effects of early feed restriction (ER) on morphology and gene expression of lateral gastrocnemius muscle. Newly hatched crossbred broiler chickens were allocated into control and ER groups, the latter being free-fed on alternate days from hatch to 14 days of age (14 d), followed by ad libitum feeding as the control group until 63 d. The lateral gastrocnemius muscle was taken at 14 and 63 d, respectively for myofibre typing by both myosin ATPase staining and relative quantification of myosin heavy chain (MyHC) mRNA for slow-twitch (SM), red fast-twitch (FRM) and white fast-twitch (FWM) myofibres. The body weight and lateral gastrocnemius weight were significantly lower in the ER group, accompanied by significantly reduced serum triiodothyronine. The ER group exhibited significantly higher SM and FRM MyHC expression at 14 d, but lower SM expression at 63 d. Myosin ATPase staining revealed a similar pattern. The percentage of SM was higher at 14 d while lower at 63 d in the ER group. These morphological changes were accompanied by changes of mRNA expression for growth-related genes. The ER group expressed lower insulin-like growth factor I (IGF-I) and higher IGF-I receptor (IGF-IR) at 14 d, yet significantly increased growth hormone receptor and IGF-IR mRNA at 63 d. These results indicate that ER may delay the slow to fast myofibre conversion as an immediate effect, but would result in a lower percentage of slow fibres owing to compensatory growth in the long term, which involves changes of mRNA expression for the growth-related genes in the muscle.

Topics: Animal Feed; Animals; Body Weight; Chickens; Eating; Gene Expression Regulation; Muscle Fibers, Fast-Twitch; Muscle Fibers, Skeletal; Muscle Fibers, Slow-Twitch; Muscle, Skeletal; Myosin Heavy Chains; Organ Size; Random Allocation; Receptor, IGF Type 1; Receptors, Somatotropin; RNA, Messenger; Thyronines

The aim of our study was to find out, which are the thyroid linked mechanisms responsible for the changes in myosin isoform composition which accompany endurance training (ET) in rodents. We studied the interaction between ET and altered sedentary group with no thyroid treatment or Se group. Six groups of rats were compared: (1) a trained group with no thyroid treatment or T group; (2) a thyroid state in rats; (3) a sedentary group rendered hypothyroid with 6-n-propyl thio uracil (H); (4) a sedentary group rendered hyperthyroid with T3 (150 microg kg(-1) every other day for 4 weeks) (St); (5) trained rats rendered hyperthyroid with T3 (150 microg kg(-1) every other day for 4 weeks) (Tt) and (6) a trained group kept euthyroid with T3 (150 ng kg(-1) every other day for 4 weeks) (Te). In each group myosin isoform composition was determined in five muscles, three locomotor muscles: (1) extensor digitorum longus, (2) superficial lateral gastrocnemius, (3) deep medial gastrocnemius, (4) an antigravity muscle, the soleus and (5) a rhytmic respiratory muscle, the crural diaphragm. Different muscles responded in a specific way to variations of the thyroid state and training.

Topics: Animals; Body Weight; Diaphragm; Electrophoresis, Polyacrylamide Gel; Male; Muscle, Skeletal; Myosin Heavy Chains; Myosin Light Chains; Myosins; Physical Conditioning, Animal; Protein Isoforms; Rats; Rats, Wistar; Thyroid Gland; Thyronines; Thyrotropin; Triiodothyronine

High doses of GH, used to induce anabolism in prolonged critically ill patients, unexpectedly increased mortality. To further explore underlying mechanisms, a valid animal model is needed. Such a model is presented in this study. Seven days after arterial and venous cannulae placement, male New Zealand White rabbits were randomly allocated to a control or a critically ill group. To induce prolonged critical illness, a template controlled 15% deep dermal burn injury was imposed under combined general and regional (paravertebral) anesthesia. Subsequently, critically ill rabbits received supplemental analgesia and were parenterally fed with glucose, insulin, amino acids, and lipids. On d 1 and d 8 after randomization, acute and chronic spontaneous hormonal profiles of GH, TSH, and PRL secretion were obtained by sampling blood every 15 min for 7 h. Furthermore, GH, TSH, and PRL responses to an iv bolus of GH-releasing peptide 2 (GHRP-2) + TRH were documented on d 0, 1, and 8. Hemodynamic status and biochemical parameters were evaluated on d 0, 1, 3, 5, and 8, after which animals were killed and relative wet weight and water content of organs was determined. Compared with controls, critically ill animals exhibited transient metabolic acidosis on d 1 and weight loss, organ wasting, systolic hypertension, and pronounced anemia on d 8. On d 1, pulsatile GH secretion doubled in the critically ill animals compared with controls, and decreased again on d 8 in the presence of low plasma IGF-I concentrations from d 1 to d 8. GH responses to GHRP-2 + TRH were elevated on d 1 and increased further on d 8 in the critically ill animals. Mean TSH concentrations were identical in both groups on d 1 and 8, in the face of dramatically suppressed plasma T(4) and T(3) concentrations in the critically ill animals. PRL secretion was impaired in the critically ill animals exclusively on d 8. TSH and PRL responses to GHRP-2 and TRH were increased only on d 1. In conclusion, this rabbit model of acute and prolonged critical illness reveals several of the clinical, biochemical, and endocrine manifestations of the human counterpart.

Topics: Animals; Body Weight; Critical Illness; Disease Models, Animal; Growth Hormone; Hemodynamics; Male; Neurosecretory Systems; Oligopeptides; Organ Size; Oxygen Consumption; Prolactin; Rabbits; Stress, Physiological; Thyronines; Thyrotropin; Thyrotropin-Releasing Hormone; Triiodothyronine; Up-Regulation

The plasma triiodothyronine (T3) and thyroxine (T4) ratios have been evaluated in kwashiorkor and diet-induced obese weaned rats. The concentrations of T3 and T4 were determined in plasma by radio-immunoassay. A significant decrease in T3 level in the order kwashiorkor < obese < control was observed. However T4 concentration was more elevated (P < 0.01) in the obese than the normal controls, while more significantly depressed (P < 0.001) in the kwashiorkor than in control animals. The T3/T4 ratio decreased in the order obese < kwashiorkor < control. It was concluded from these studies that kwashiorkor and diet-induced obesity not only interfere with the absolute concentration of the thyroid hormones but also alter the T3/T4 ratio. The altered T3 and T4 ratio perhaps contributes to the maintenance of the isoenergetic state rather than to the promotion of negative or positive energy balance in kwashiorkor and obese subjects respectively.

Topics: Animals; Body Weight; Diet, Protein-Restricted; Dietary Carbohydrates; Dietary Proteins; Female; Kwashiorkor; Male; Obesity; Radioimmunoassay; Rats; Rats, Sprague-Dawley; Thyronines; Triiodothyronine

Male Sprague-Dawley rats were fed a selenium-deficient yeast-based laboratory diet or a control diet for 6 wk. The tissue type I 5'-monodeiodinase (5'-MDI) activity and the immunoassayable 5'-MDI were significantly (P < 0.05) reduced in the liver and the kidney but not in the thyroid of selenium-deficient rats. The mean serum concentrations of thyroxine sulfate (T4S), 3,3',5'-triiodothyronine sulfate (T3S), and reverse T3 sulfate (rT3S) (ng/dl) were significantly increased in selenium-deficient rats (15.7, 59.4, and 22.8, respectively, n = 12) compared with control rats (< 1.0, 18.5, and 9.1, respectively, n = 12, P < 0.01). Kinetic studies were carried out during a constant infusion of unlabeled sulfated iodothyronines (T4S, T3S, or rT3S, n = 5-6/group) at a rate of 1 microgram/h by Alzet minipump for 48 h. The data showed that elevated serum concentrations of T4S or T3S in the selenium-deficient rat are due both to reduced metabolic clearance rate (MCR, mean, l.kg-1.day-1, 7.4 for T4S and 4.5 for T3S in selenium deficiency vs. 12 and 9.2, respectively in controls, P < 0.05) and increased production rate (mean, microgram.kg-1.day-1, 1.2 for T4S, and 2.7 for T3S in selenium deficiency vs. 0.12 and 1.7, respectively, in the controls, P < 0.05). However, the increased serum rT3S concentration in selenium-deficient rats is due mainly to reduced MCR (mean, l.kg-1.day-1, 34 vs. 67 in controls, P < 0.05) and its daily production rate remained unchanged in selenium deficiency (mean, microgram.kg-1.day-1, 7.6 vs. 6.1 in the control group, P > 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Animals; Body Weight; Female; Glutathione Peroxidase; Iodide Peroxidase; Kinetics; Male; Organ Size; Rats; Rats, Sprague-Dawley; Selenium; Sex Characteristics; Sulfates; Thyroid Hormones; Thyronines

Very often, an impact on the intracellular metabolism of iodothyronines and more precisely on microsomal deiodinases is evoked to explain thyroid hormone (TH) serum level alterations occurring with numerous drugs. Among them, three at least are also known to interfere with other hepatic microsomal enzymes, amiodarone (AMI), phenobarbital (PHE) and propranolol (PRO). Starting from this statement, we have examined the effects of 5 macrolides on TH serum level and on hepatic 5' type 1 deiodinase (5'DI) in vivo in rat. Rats were treated orally for eight days either with 200 mg/kg macrolides--erythromycine (ERY), troleandomycine (TRO), josamycine (JOS), midecamycine (MID) and spiramycine (SPI)--, or with AMI (45 mg/kg), PHE (50 mg/kg) or PRO (20 mg/kg), these 3 latter drugs for comparative purpose. Total T4, T3 and rT3 were determined by RIA. Hepatic 5'DI was evaluated by measuring released radioactive iodide from a reverse T3 monolabelled with 125I used substrate. Compared to control group, ERY and TRO decreased T4 (respectively by 28 and 16%) and from these two, only TRO decreased T3 (23%). With JOS, the only major modification was an increment of T3 (26%). AMI gave a typical alteration with a high T4 (130%), a low T3 (26%) and a high rT3 (376%). 5'DI was statistically inhibited by AMI (85%), JOS (49%), TRO (43%) and ERY (35%). The other drugs showed no significant effect. So, three macrolides have both altered TH serum level and 5'DI, findings which have never been reported before. The precise mechanism of this action remains unknown and the resulting effect, being far from the one observed with AMI, tends to demonstrate, for macrolides, an absence of correlation between the extent of 5'DI inhibition and TH serum profile. Besides, comparative analysis of the results observed with macrolides, AMI, PHE and PRO argues against any relationship between 5'DI and cytochrome-P450 monooxygenases.

Topics: Amiodarone; Animals; Anti-Bacterial Agents; Body Weight; Iodide Peroxidase; Liver; Macrolides; Male; Phenobarbital; Propranolol; Rats; Rats, Inbred Strains; Thyroid Hormones; Thyronines

The influence of bromide on thyroid function was studied in iodine-deficient rats, fed on a diet containing 4-16 g/kg sodium bromide for 4 weeks. Measurement of total and free thyroxine and thyroid-stimulating hormone in blood, as well as the thyroid hormones in the thyroid gland, revealed typical signs of hypothyroidism, which were significantly enhanced by bromide intake. Special attention was paid to the possible formation of bromo/iodosubstituted thyronines in the thyroid. These measurements were performed by high-performance liquid chromatography with off-line radioimmunoassay detection. Such thyroid hormone analogues could be detected in all groups of animals with additional bromide intake, but the amounts were found to be too low to compensate adequately for the reduced amounts of thyroid hormones. The results of this study also indicate that bromide toxicity is dependent upon the state of the iodine supply, which should be taken into account for evaluation of acceptable daily intake values for bromide.

Topics: Animals; Body Weight; Bromides; Chromatography, High Pressure Liquid; Feeding Behavior; Female; Iodides; Iodine; Male; Rats; Rats, Inbred Strains; Sodium; Sodium Compounds; Spectrophotometry, Ultraviolet; Thyroid Gland; Thyroid Hormones; Thyronines; Thyrotropin

3,5-Dimethyl-3'-isopropyl-L-thyronine (DIMIT)-induced fetal hyperthyroid rats showed a marked accumulation of intracellular tubulin content in the cerebral cortex, hypothalamus, and cerebellum at 1 day old. When the fetuses were transplacentally radio-thyroidectomized with the administration of [131I]-Na, the brain weight was not changed at 1 day old. The DNA content was not affected by the radio-thyroidectomy (Tx), but intracellular RNA concentration (per DNA) was increased in the hypothalamus and cerebellum at that age. The DIMIT-supplement to Tx-fetuses failed to restore these abnormal values to normal. Delayed effects of the fetal Tx were observed in 11-day-old infants. These neonates showed decreased weight gain in the body, brain, cerebral cortex, and cerebellum. The DNA content (per wet tissue) was higher in the hypothalamus and cerebellum. The intracellular concentrations of RNA and tubulin (per DNA) were significantly decreased in the hypothalamus. These values were restored to normal by the administration of L-thyroxine(T4) to rats between 1 and 10 days old. These results demonstrate that fetal nervous tissues are sensitive to changes in thyroid functions. The different manner of response to the hormonal states among the brain areas may reflect that each nervous tissue has a specific critical period for thyroid hormones during development.

Topics: Animals; Animals, Newborn; Body Weight; Brain; DNA; Female; Fetus; Organ Size; Pregnancy; Rats; Rats, Inbred Strains; RNA; Thyroid Gland; Thyroidectomy; Thyronines; Thyroxine; Tubulin

Rats were given amiodarone (50 mg X kg-1 X day-1, orally) for 4 weeks and the distribution of ventricular isomyosins, a sensitive index of the effects of thyroid hormones on cardiac tissue, was analyzed. Amiodarone treatment induced a marked increase in both T4 and rT3 and tended to decrease T3 serum levels. At the pharmacologically active dosage we used, the drug induced a moderate redistribution of ventricular isomyosins in favour of V, at the expense of V1. Our results do not support the hypothesis that the major mechanism of action of amiodarone is mediated through hypothyroid-like effects.

Topics: Aging; Amiodarone; Animals; Body Weight; Heart; Isoenzymes; Male; Myocardium; Myosins; Rats; Rats, Inbred Strains; Thyronines

3,5-Dimethyl-3'-isopropyl-L-thyronine (DIMIT) and 3,5-diiodo-3'-isopropylthyroacetic acid (IpTA2), two thyroid hormone analogs, have been tested in genetically obese Zucker rats and their lean littermates, in comparison with thyroxine (T4) and triiodothyronine (T3) for their thyromimetic activities on body weight gain and lipid levels in serum and liver. The compounds were administered for 9 weeks by orogastric tube to 6- to 8-week-old animals. While body weight gain remained practically unchanged in the lean rats, it decreased significantly in the obese individuals, especially with IpTA2. The serum lipid concentrations were also decreased in the obese rats in comparison with their lean littermates, especially with DIMIT. The connection observed between the structure of DIMIT and IpTA2 on one hand and their effects on the other is in good agreement with previous studies. Our results confirm that the iodine substituents are not necessary for thyromimetic activity and demonstrate that the isopropyl substituent in 3' plays an important role in the serum lipid-lowering effect of the thyroid hormone analogs tested.

Topics: Animals; Body Weight; DNA-Directed RNA Polymerases; Female; Lipid Metabolism; Liver; Obesity; Rats; Rats, Zucker; Structure-Activity Relationship; Thyronines; Thyroxine; Triiodothyronine

This study was designed to examine the in vivo reduction of the N-oxidation products of nicotine metabolism in rats. Male Fischer-344 rats were divided into one control and three experimental groups (n = 20). Each treatment group received either 0.02% trans-nicotine N'-oxide, 0.02% cis-nicotine N'-oxide, or 0.02% nicotine N,N'-dioxide in drinking water for 3 wk. After 7 d of metabolite administration, plasma nicotine levels in the trans-nicotine N'-oxide group rose to twice that of the cis-nicotine N'-oxide or nicotine N,N'-dioxide group. Plasma cotinine [1-methyl-5-(3-pyridinyl)-2-pyrrolidinone] concentrations reached maximum levels during wk 1 in the cis-nicotine N'-oxide and nicotine N,N'-dioxide groups but continued to increase for another 7 d in the trans-nicotine N'-oxide group. At d 15 and again at d 21, rats from each group (n = 10) were placed in metabolism chambers and given 50 ml tap water over a 24-h period. Analysis of urine obtained from a metabolism-chamber study conducted after 15 d of consumption revealed concentrations of nicotine in the trans-nicotine N'-oxide group that were 3 times higher than cis-nicotine N'-oxide-treated animals. Urinary cotinine levels were similar in all three groups. Results from a second chamber study (d 21) showed similar urinary nicotine and cotinine values in all treatment groups. Plasma total triiodothyronine (TT3) concentrations were reduced in all treatment groups during the first week. Plasma total thyronine (TT4) concentrations were reduced (p less than 0.05) in the trans-nicotine N'-oxide and cis-nicotine N'-oxide treatment groups during the first week. Plasma total thyronine (TT4) concentrations cis-nicotine N'-oxide is presented. An analytical method for separation of nicotine, cotinine, and cis- and trans-nicotine N'-oxide, as well as cis- and trans-nicotine N,N'-dioxide, is also outlined.

Topics: Age Factors; Animals; Body Weight; Cotinine; Male; Nicotine; Oxidation-Reduction; Oxides; Rats; Rats, Inbred F344; Thyronines; Triiodothyronine

Studies were conducted to determine if brief exposure, in utero, to high levels of T4 or to the synthetic thyromimetic agent 3,5-dimethyl-3'-isopropyl-L-thyronine (DIMIT) can produce permanent disruption of the thyroid control system in a manner analogous to the changes in the "set point" reported to occur due to neonatal T4 exposure in the "neo-T4 syndrome". If such a change were to occur, it could explain the persistent thyroid disturbances seen in the progeny of hypothyroid mother rats. These latter progeny are exposed in utero to both low and high serum T4 levels. Maternal T4 treatment produced a 4-fold elevation in fetal serum T4 accompanied by a large decrease in serum TSH levels. The brief treatment in utero with high doses of T4 or of DIMIT resulted in higher neonatal mortality and the T4-treatment produce subsequent growth stunting. These treatments resulted in suppression of the fetal/neonatal thyroid which was very apparent at 5 days of age. At 30 days post-partum, the thyroid control system of the progeny of the T4 and DIMIT-treated animals was still abnormal with low serum T4 levels accompanied with normal serum TSH and T3 levels. At 60 days of age, serum T4 levels remained low in the progeny of the T4-treated animals and the TSH response to TRH was subnormal in both the progeny of the T4-treated and the DIMIT-treated animals. However, serum and pituitary TSH and serum T3 were normal. The thyroid control system of the rat is sensitive to prenatal exposure to hyperthyroxinemia as it is to postnatal exposure.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Animals; Body Weight; Female; Fetus; Pregnancy; Prenatal Exposure Delayed Effects; Rats; Rats, Inbred Strains; Thyroid Gland; Thyronines; Thyroxine; Time Factors; Triiodothyronine

Our experiments show that the T3 nonhalogenated analog 3,5-dimethyl-3'-isopropyl-L-thyronine (DIMIT) exhibits the general activities of thyroid hormones. DIMIT delivered to hypothyroid Rat by constant infusion or sc injections increases bodyweight gain, BMR before or after epinephrine and phosphorylative oxidation of liver mitochondria.

Topics: Animals; Basal Metabolism; Body Weight; Hypothyroidism; Infusions, Parenteral; Male; Mitochondria, Liver; Rats; Rats, Inbred Strains; Thyronines

Thirty Holstein heifer calves averaging 120 days of age and 102 kg of body weight were allocated to one control and four treatment groups of six each. Iodine, as ethylenediamine dihydriodide, was mixed 1:9 with dextrose and administered once daily atop feed at .625, 1.25, 2.5, or 5.0 mg iodine per kilogram body weight. Calves were housed individually in unheated, well-ventilated barns and fed complete mixed feeds containing less than 1 ppm iodine. Feed intakes were recorded daily and body weights weekly. Jugular venous blood was collected from iodine treated calves at 0, 4, 8, and 12 wk of the experiment and analyzed for iodine, thyroxine, and triiodothyronine of plasma. Feed intake per unit body weight and per unit gain were not significantly different between treated and control calves. However, daily feed intake and average daily gain decreased slightly at the highest iodine intake. Thyroxine and triiodothyronine were not different among treatments. Thyroxine declined in all calves from 0 to 12 wk. Thyroxine of calves fed 5.0 mg of iodine per kilogram body weight decreased more than of calves fed less iodine. Iodine intake as high as 5.0 mg/kg body weight was tolerated without morbidity, although a minor effect on performance and thyroid activity was indicated.

Topics: Animals; Body Weight; Cattle; Diet; Ethylenediamines; Female; Iodides; Iodine; Thyroid Gland; Thyronines; Triiodothyronine

Topics: Adrenal Glands; Animals; Body Weight; Dose-Response Relationship, Drug; Growth; Heart; Heart Rate; Iodine Isotopes; Kidney; Male; Organ Size; Oxygen Consumption; Pituitary Gland; Rats; Spleen; Thyroidectomy; Thyronines; Thyroxine

Topics: Amino Acids; Animals; Body Weight; Chromatography, Ion Exchange; Darkness; Diiodotyrosine; Iodine; Light; Male; Monoiodotyrosine; Organ Size; Pituitary Gland; Rabbits; Thyroid Gland; Thyroid Hormones; Thyronines; Thyrotropin; Time Factors

Topics: Adaptation, Physiological; Animals; Body Weight; Chromatography; Deficiency Diseases; Diet; Diiodotyrosine; Homeostasis; Hypophysectomy; Injections; Iodine; Iodine Isotopes; Organ Size; Rats; Thyroid Function Tests; Thyroid Gland; Thyronines; Thyrotropin; Thyroxine; Time Factors; Triiodothyronine

Topics: Adrenal Glands; Animals; Body Weight; Corticosterone; Hydroquinones; Injections, Intravenous; Male; Methods; Organ Size; Propionates; Pyrogens; Rats; Thyroid Hormones; Thyronines; Thyroxine; Time Factors; Triiodothyronine

Topics: Body Weight; Body Weights and Measures; Environment; Humidity; Metabolism; Methylthiouracil; Pharmacology; Rats; Research; Stress, Physiological; Temperature; Thyronines; Thyroxine; Triiodothyronine

Topics: Animals; Body Weight; Body Weights and Measures; Diet; Metabolism; Oxygen Consumption; Propylthiouracil; Rats; Thyroid Hormones; Thyronines; Thyroxine; Triiodothyronine