vitamin-a2 and 3-4-didehydroretinyl-acetate

Periodic supplementation to infants and young children is encouraged in developing countries by the WHO. We investigated vitamin A (VA) in extrahepatic tissues of piglets after supplementation with retinyl acetate to determine long-term storage. 3, 4-Didehydroretinyl acetate (DRA) as a tracer was used to evaluate uptake from chylomicra in 4 h. Sows were fed a VA-depleted diet throughout pregnancy and lactation. Male castrated piglets (n = 28, 11.6 +/- 0.5 d) from these sows were weaned onto a VA-free diet for 1 wk, assigned to 4 groups, and dosed orally with 0, 26.2, 52.4, or 105 micromol VA. After 10 d, 5.3 micromol DRA was administered to determine short-term uptake of 3, 4-didehydroretinol (DR). Four hours later, piglets were killed; adrenal glands, kidney, lung, and spleen were collected and analyzed for retinol and DR. Retinol concentrations of kidney and adrenal gland were higher than control, but treated groups did not differ. Retinol concentration was highest in kidney (1.70-2.52 nmol/g), followed by adrenal gland (0.30-0.48 nmol/g), lung (0.15-0.21 nmol/g), and spleen (0.11-0.15 nmol/g). Total retinol in kidney and spleen was different among the groups (P < 0.05). Unesterified retinol was the major VA form; the percent retinol of total VA was lowest in adrenal glands. DR did not differ among the groups. In 4 h, the minimum estimated chylomicron contribution to tissue DR was 63-280% higher than the maximum DR exposure from retinol-binding protein. Constant dietary intake may be important in maintaining VA concentrations in extrahepatic tissues.

Topics: Adrenal Glands; Animals; Chylomicrons; Dose-Response Relationship, Drug; Female; Kidney; Liver; Lung; Male; Spleen; Swine; Tissue Distribution; Vitamin A

The modified-relative-dose-response (MRDR) test, which requires a blood sample after dosing with 3,4-didehydroretinyl acetate (DRA), has been used to determine vitamin A (VA) status of individuals and groups worldwide. Less invasive methods using milk are in development in a swine model. Swine are a good choice for studying VA metabolism because their gastrointestinal anatomy, morphology, physiology, and VA requirements are similar to those of humans. In this study, DRA was used as a VA tracer in lactating sows to follow the metabolism of newly ingested VA. Lactating sows (n = 6) were administered 35 micromol DRA after overnight food deprivation. Blood and milk were collected at 0, 1.5, 3, 5, 7, 9, 24, and 48 h; livers were obtained at the time of killing. Samples were analyzed for didehydroretinol (DR), retinol (R), and didehydroretinyl esters (DRE). Serum DR:R was compared with that in milk and other VA indicators. DRE rapidly increased in serum, corresponding to chylomicra, whereas DR increased at a slower rate corresponding to the holo-DR:retinol-binding protein complex released from the liver. An estimated 10-20% of the dose was irreversibly lost in milk over 48 h. The mean MRDR value was 0.018 +/- 0.013 at 5 h and the mean liver VA was 0.73 +/- 0.21 micromol/g, both signifying sufficient stores. Milk and serum DR:R values were directly correlated (r = 0.64, P < 0.0001). Thus, DR:R values in milk may be a potential alternative to serum in determining VA status in lactating women. Future work is required in VA-deficient sows and women of varying VA status to determine DR trafficking and to compare DR:R values in milk with those in serum.

Topics: Animals; Esters; Female; Lactation; Liver; Milk; Nutritional Status; Swine; Time Factors; Vitamin A