RELATION OF ARGININE NUTRITION TO MAMMARY-GLAND DEVELOPMENT IN THE RAT

Experiments were conducted to determine the effect of dietary arginine on growth and mammary gland development in rats. Gravid rats fed arginine-free diets remained in positive nitrogen balance but lost body weight. Arginine requirement based upon nitrogen retention and body weight gain was estimated to be 0.55%. Number of pups born and their birth weight were not affected by dietary arginine. Consumption of an arginine-free diet during gestation significantly reduced mammary gland growth which was associated with depressed mammary RNA and DNA concentrations. Restricting feed intake by pair-feeding resulted in body weight loss; however, mammary gland mass and nucleic acid content were significantly higher than that of rats fed an arginine free diet. Arginase and S-adenosyl-L-methionine decarboxylase activities were not affected by dietary arginine concentration; arginine's effect on ornithine decarboxylase was inconsistent. This study demonstrated that dietary arginine is required for optimal mammary gland development during gestation. It appears that the effect of arginine is not mediated directly via rate limiting enzymes of polyamine biosynthesis.