Lung retinyl ester is low in young adult rats fed a vitamin A deficient diet after weaning, despite neonatal vitamin A supplementation and maintenance of normal plasma retinol.
Although it is understood that plasma retinol concentration is not proportional to the concentration of vitamin A stored in liver, plasma retinol still is often used as an indicator of vitamin A status. An aim of vitamin A supplementation strategies is to maintain plasma retinol concentration in a range considered adequate, generally >1.05 micromol/L in humans, with some adjustment for age. In the present study in rats, we addressed the following question: Does lung vitamin A increase postnatally, as is observed in rats fed a vitamin A-adequate diet, if plasma retinol is maintained at approximately 1 micromol/L by supplementation at neonatal age, but the weaning diet is deficient in vitamin A? We treated rats on postnatal d 6, 7, and 8 with placebo (oil), vitamin A, retinoic acid (RA), and a nutrient-metabolite combination of vitamin A and RA, VARA, after which tissues were analyzed on d 9. Other rats treated identically as neonates were fed a vitamin A-deficient diet from 3-9 wk of age, and in parallel, another group of rats was fed a vitamin A-adequate diet. Although supplementation with vitamin A or VARA elevated liver and lung retinyl esters (RE) on d 9 (P < 0.0001), and prevented the fall in plasma retinol to <1 micromol/L by 9 wk of age, when the diet was vitamin A-deficient, lung RE fell to 28% of the concentration present in the lungs of rats fed the vitamin A-adequate diet (P < 0.0001). We infer that the lungs depend, at least in part, on the uptake of dietary vitamin A, probably from chylomicrons, to develop RE stores in the postweaning growth period.
Ross
A Catharine
AC
Department of Nutritional Sciences, Pennsylvania State University, University Park, PA 16802, USA. acr6@psu.edu
Li
Nan-qian
NQ
D000818:Animals; D000831:Animals, Newborn; D004032:Diet; D019587:Dietary Supplements; D004952:Esters / Q000378:metabolism; D005260:Female; D008099:Liver / Q000187:drug effects / Q000378:metabolism; D008168:Lung / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D014212:Tretinoin; D014801:Vitamin A / Q000097:blood* / Q000378:metabolism / Q000494:pharmacology*
D004952:Esters; D014801:Vitamin A; D014212:Tretinoin