Effect of protein quantity and quality on plasma response to an oral dose of vitamin A as an indicator of hepatic vitamin A reserves in rats
Underwood, B.A.
Journal of Nutrition 110(8): 1635-1640
1980
ISSN/ISBN: 0022-3166 PMID: 7400853 Document Number: 155552
Rats were fed on diets deficient or sufficient in vitamin A (retinol equivalents 3 mg/kg) containing 7% rice protein or 7% casein. Rats on vitamin A-free casein diets were pair-fed with the comparable group given rice protein. Growth of rats given rice protein was less than that of those given casein, regardless of vitamin A status. Plasma vitamin A values after 34 days of feeding were similar, and in normal range (above 40 mu g/100 ml), for the vitamin-A supplemented rice protein group and the unsupplemented casein groups, despite widely varying liver reserves (more than 130 against less than 20 mu g/g). Groups given no supplement had similar liver reserves, 10 to 20 mu g/g, regardless of protein source, but widely different plasma values. The relative dose response (RDR) during 5 h to a small, 20 mu g, oral dose of vitamin A was under 25% for all groups on day 34. On day 49, plasma vitamin A concentrations had dropped and were similar for both vitamin A-deprived groups, about 25 to 30 mu g/100 ml, as were liver values (less than 10 mu g/g) and the RDR (above 50%). In contrast, the vitamin A-supplemented group given rice protein had an RDR of less than 50%.