Effects of Zinc and Vitamin A Deficient Diets on the Hepatic Mobilization and Urinary Excretion of Vitamin A in Rats

Abstract

Weanling rats were fed diets deficinet in zinc (ZD), vitamin A (AD), or both (ZAD) for 3 weeks. Each then received 20 µg of 11.12-³H-retinyl acetate. Plasma retinol was monitored for radioactivity for 5 hours and urine for 6 days. Rats were killed and measurements made of plasma and liver vitamin A and plasma zinc. Plasma vitamin A was depressed but growth was not affected in AD rats compared to pari-fed controls. Radioactivity appeared most rapidly in the plasma retinol fractions of the two vitamin A-depleted groups (AD and ZAD) and was excreted most rapidly in the urine of these same groups. Zinc-deficient diets (ZD and ZAD) caused depressed plasma levels of zine and vitamin A and growth retardation greater than in pair-fed controls. However, zinc deficiency had no effect on mobilization of newly-ingested vitamin A or urinary excretion of labeled metabolites. Liver stores of vitamin A were lower for ZD rats than for controls. The data indicate that zinc deficiency is not a limiting factor in hepatic vitamin A release except as it influences growth and body demand for the vitamin. The data also suggest that newlyabsorbed vitamin A is mobilized and utilized in preference to that previously stored in the liver.