Differential effects of hydrocortisone on alanine aminotransferase isoenzymes of the cerebral hemispheres and cerebellum of rats during growth, development, and senescence.

The activities and induction patterns of the isoenzymes of alanine aminotransferase (AAT) of the cerebral hemispheres and cerebellum of rats of various ages were studied. The activities of both the soluble (s-) and mitochondrial (m-) isoenzymes of ATT of the cerebral hemispheres and cerebellum were highest in the immature rat and decreased significantly thereafter with increasing age. Adrenalectomy decreased, and hydrocortisone administration increased significantly, the activity of s-AAT in both cerebral hemispheres and cerebellum of immature, adult, and senescent rats. However, these treatments resulted in significant changes in the activity of m-AAT in both tissues of the immature rat only. The hormone-mediated induction of these isoenzymes was actinomycin D-sensitive.