Effect of Stress from High Protein Diets on Vitamin A Metabolism in Chicks

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Abstract
High protein diets fed to young chicks for 4 weeks produced a stress as evidenced by hypertrophy, hyperactivity and depletion of phospholipid content of the adrenal cortex and at the same time, caused an increased demand on vitamin A nutrition. No adrenal hypertrophy nor hyperactivity occurred in 4-week-old chicks fed high protein diets and simultaneously injected daily with corticosterone. However, daily injections of corticosterone increased the level of vitamin A in the blood plasma and generally caused a decrease in liver vitamin A levels. Although vitamin A deficiency was not found to affect adrenal size or corticoid production the in vitro addition of vitamin A to incubated adrenals from chicks fed high protein diets caused a marked increase in corticosterone production. Liver glycogen formation during the first 4 hours of refeeding high protein-fed chicks after a one-day fast was not impaired by vitamin A deficiency. However, liver glycogen per gram of total feed consumption was significantly decreased in vitamin A-deficient chicks 24 hours after refeeding the high protein diet following the fasting period. These results indicate an important association between vitamin A nutrition and stress produced by high protein feeding.