EFFECT OF REPEATED INJECTION OF SOMATOMEDIN-C ON DRUG-METABOLIZING ENZYME-ACTIVITIES IN RATS

The effect of somatomedin C on the hepatic drug-metabolizing enzyme sy stem in rat liver after sc injection, a clinically applicable dosing r oute, was studied. Although liver weight was slightly increased after somatomedin C (1 mg/kg) was injected for 7 days, no significant change s were observed in other dosing group (0.1 and 10 mg/kg). There were n o significant effects of somatomedin C on cytochrome P-450 and b(5) co ntents, and NADPH-cytochrome c reductase, aminopyrine demethylase, ani line hydroxylase, and ethoxyresorufin deethylase. Additionally, somato medin C treatment did not affect the activities of 2 alpha-, 2 beta-, 6 beta- and 16 alpha-hydroxytestosterone and androstenedione formation from testosterone. Changes relation to dosing period were also examin ed with 1 mg/kg of somatomedin C. in this case, hepatic levels of cyto chrome P-450 and b(5), NADPH-cytochrome c reductase and drug oxidation s did not differ significantly among groups treated for 3, 7, or 14 da ys. These results suggest that somatomedin C has no effect on the hepa tic mixed-function oxidase, system.