Plasma glucose and glucagon concentrations in the hibernating hedgehog

Abstract

Plasma glucagon (IRG) and glucose were measured in hedgehogs during the lethargy, arousal, and active periods. Glucose and glucagon concentrations were lower during lethargy than in the active animals. A rapid rise in IRG concentrations followed by a plasma glucose augmentation were measured during the rewarming period. The catabolism of exogenous glucagon was much slower in the hypothermic than in homeothermic animals. Pharmacological doses of glucagon induced a slight, delayed but significant effect on glucose concentrations in hypothermic hedgehogs. In the arousing and in the active animals, a frank and rapid hyperglycemic effect of glucagon was observed. This is consistent with an efficient contribution of endogenous glucagon to the restoration of active metabolic processes during the spontaneous arousal although pharmacological doses of glucagon did not trigger and did not accelerate rewarming. The regulation of A cells by glucose was studied by glucose and insulin administration in the lethargic, arousing, and active hedgehogs. Hyperglycemia only decreased glucagon secretion in the active animals and at the end of rewarming. Similarly, acute insulin-induced hypoglycemia stimulated A-cell secretion in the active animals and at the end of rewarming while insulin did not induce hypoglycemia in lethargic hedgehogs. It is suggested that when the body temperature of arousing hedgehogs draws near the homeothermic temperature, the regulation of A cells by glucose is similar to that of nonhibernating mammals. Other metabolic and hormonal factors may interfere during lethargy and at the beginning of arousal.