Short-term effects of ovine growth hormone on plasma glucose, free fatty acids and ketones in sheep

Abstract

Rapid intravenous administration of 8 or 10 mg. ovine GH (0.13–0.25 mg./Kg.) to intact sheep usually, but not invariably, resulted in an “insulin-like” phase lasting up to 1 hour during which time plasma glucose, FFA and ketone concentrations declined. This was followed by a period in which FFA concentration increased rapidly to a maximum 8 hours after injection. Glucose and ketone concentrations also usually increased during this period. Concentrations of glucose, FFA and ketones had returned to normal by 24 hours after the injection. Hypophysectomized sheep maintained with cortisone and thyroxine were more sensitive to intravenous GH. Effects on FFA, comparable to those seen in intact sheep were obtained with half the GH dose given intact animals. In hypophysectomized sheep not given GH previously, the initial hypoglycemia was marked and, despite a partial recovery, glucose concentration remained below control values for more than 12 hours. After subsequent GH injections, hyperglycemia similar to that seen in intact animals followed a brief hypoglycemic phase. Neither prolonged fasting nor the prior diet had marked effects on the FFA response to GH in intact animals. The hyperglycemic effect of GH was greater in sheep previously fed ad libitum than in those fed a maintenance ration, and was negligible in sheep fasted 6 days before GH injection. In sheep treated with cortisol, however, injection of GH after a fast of 6 days resulted in a marked increase in plasma glucose after the initial “insulin-like” phase. Cortisol treatment had little effect on the lipolytic action of GH.