INFLUENCE OF LIVER RESECTION AND REGENERATION ON SOMATOMEDIN (SULPHATION FACTOR) ACTIVITY IN SERA FROM NORMAL AND HYPOPHYSECTOMIZED RATS

Abstract

Somatomedin (SM) activity has been studied in the plasma of normal and hypophysectomized rats following partial hepatectomy. In normal rats a rapid disappearance of SM-activity was observed reaching a 75 per cent decrease 4–6 hours after surgery. The remaining lobes, 30 per cent of the total livers, left after hepatectomy gained in weight and were fully restored after 5–6 days. The SM-activity in the plasma from these rats slowly returned to normal level at the same rate as restoration of the resected liver tissue. In hypophysectomized rats a 35 per cent increase in relative liver weight (weight of liver in per cent of body weight) was observed 6 days after surgery in spite of the absence of the pituitary gland. Partially hepatectomized hypophysectomized rats given a pharmacological dose of human growth hormone were found to produce 40 per cent less SM-activity than control hypophysectomized rats when injected 24 hours after surgery. Administration of cycloheximide to hypophysectomized rats before growth hormone administration totally inhibited the production of SM-activity. It is concluded that the production of somatomedin in the rat is dependent on a normal liver function and that somatotrophic hormone is not an absolute necessity in the regenerating process.