Factors affecting the levels of the L-serine O-sulphate-degrading system of rat liver

Abstract

1. 1. Alterations in the protein composition of experimental diets had no effect on the hepatic levels of the L-serine O-sulphate degrading system in the rat. Similarly the administration of either hydrocortisone or prednisolone to experimental animals did not alter the hepatic enzyme levels. 2. 2. The intraperitoneal administration of thyroxine (200–600 μg) led to a decrease in enzyme levels over a maximum period of 15 days. 3. 3. Thyroidectomy produced an increase in enzyme levels which was restored to normal following the administration of physiological doses of thyroxine. 4. 4. Intraperitoneal administration of glucagon gave rise to an elevation in enzyme levels. No corresponding changes were observed in response to the administration of 3′5′-cyclic AMP, adrenaline, insulin or aminophylline. 5. 5. Actinomycin D when administered alone to experimental animals had no effect on hepatic enzyme levles. When administered concomitantly with glucagon a marked decrease in enzyme levels was observed. 6. 6. Incubation of glucagon in vitro with a rat liver homogenate leads to a marked decrease in the L-serine O-sulphate degrading activity. No effect was observed when glucagon was similarly incubated with a supernatant preparation.