Effects of experimental diabetes on rat hepatic phenylalanine hydroxylase in vivo

1. The stimulated levels of phenylanine hydroxylase activity in liver extracts from streptozotocin-induced diabetic rats (Donlon and Beirne, 1982) have been correlated with an increased rate of phenylalanine catabolism in vivo. 2. The levels of hepatic phenylalanine hydroxylase protein in diabetic rats become elevated. This effect is not seen in diabetic animals concurrently treated with insulin. 3. The rate of synthesis of liver phenylalanine hydroxylase in 5-day diabetics is 260% that of control animals. 4. These observations are discussed with reference to the regulation of hepatic phenylalanine hydroxylase and phenylanine metabolism in rats.