The Activities of Some Enzymes of Tryptophan Metabolism in Fetal, Neonatal and Adult Rat Liver and Kidney. Ii. Kynurenine 3-hydroxylase Activity.

(1) In fetal rat liver and kidney, kynurenine 3-hydroxylase activity was absent. It began to appear after birth and reached the adult level when the body weight of rat became about 50 g (approximately 25 days after birth). (2) In kidney, the change of kynurenine 3-hydroxylase activity after the daily subcutaneous injection of progesterone or estradiol-17 f3 in a dose of 2.7 mg or 30 pg per 100 g of body weight, respectively, on the back for one and two weeks was almost same, while in liver, the inhibition of its activity was much more enhanced by the treatment for two weeks than one week. (3) The results of this experiment and the previous report 4l indicate that anthranilic acid, derived from kynurenine by kynureninase, may play a significant