Studies on metabolism of vitamin A. 5. Dietary protein content and metabolism of vitamin A

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Abstract
Growing rats separately maintained on diets containing 5, 10 and 20% of casein, when given a single massive dose of vitamin A acetate, showed that the efficiency of absorption of the vitamin increases progressively with the increase in the dietary protein content. The enzyme activities of the pancreas and intestinal mucosa hydrolysing and synthesizing vitamin A esters, and of the liver oxidizing retinene, were progressively decreased with the lowering of the dietary protein content. When adult male rats with considerable liver reserves of vitamin A were maintained on the diets of the 3 protein contents, the blood albumin and vitamin A concentrations of those receiving the diets containing 5 and 10% of protein fell with the progress of time, those rats receiving the least protein showing the maximum decrease. The decreased blood concentrations were restored on allowing the rats to receive the 20% protein diet.