Influence of age, adrenalectomy, and corticosteroids on hepatic transaminase activity
The activity of alanine-α-ketoglutarate transaminase in rat liver was found to be uniform during the first 6 weeks of life, increasing thereafter until at 48 weeks of age the specific activity was seven times greater than in the immature rat. In rats varying in age from 4 days to 24 weeks, treatment with 1 mg of cortisol for 4 days resulted in significant increases in hepatic alanine transaminase activity. Female rats were less responsive to cortisol treatment than were males. Fetal rat liver had significantly lower alanine transaminase activity than did newborn animals and the activity of this enzyme in fetal liver was not altered by cortisol treatment. Adrenalectomy of adult male rats, but not immature male rats, resulted in a decrease in alanine transaminase activity; after 48 hr, enzyme activity was depressed to levels found in unoperated immature rats. The sensitivity of the adrenalectomized animals to cortisol administration was comparable to that of intact animals. In contrast, the aspartate-α-ketoglutarate transaminase was not appreciably altered following cortisol treatment or adrenalectomy and did not increase with age.