Hypoglycemic responses to insulin in normothermic and hyperthermic young dogs

The present study was conducted in 10 healthy young dogs in which pattern of hypoglycemia to injected insulin (0.12 U/kg I.V.) was studied at normothermic (38.5 degrees C) and hyperthermic (42.5 degrees C) body temperatures. Average maximum fall in plasma glucose concentration from the control level was 44.3% and 53.8% in normothermic and hyperthermic dogs respectively. The hypoglycemic response to injected insulin was much greater and prolonged in hyperthermic dogs. The recovery of plasma glucose to preinjection level was also very sluggish and incomplete in these dogs. The above changes in hyperthermic animals may be due to enhanced secretion of insulin, as well as an increased sensitivity to injected insulin. The slow recovery of plasma glucose to preinjection level following insulin administration in hyperthermic dogs would indicate inefficient feedback mechanisms which normally operate to raise the plasma glucose during hypoglycemia.

Effect of hyperthermia on glucose homeostasis in young dogs. An experimental study

Hyperthermia was produced in healthy anaesthetized young dogs by keeping them in a theromostatically controlled chamber, and the effects on blood glucose concentration were studies. The blood glucose levels decreased significantly at body temperatures of 40.5 degrees C and 42.5 degrees C. The decrease was greater at the latter temperature. Intravenous glucose tolerance tests were performed to study the rates of glucose utilization during hyperthermia. The calculated fractional rates of disappearance of glucose (Kt values) were found to be significantly higher in dogs having a body temperature of 42.4 degrees C. The cause of hypoglycemia produced at high body temperature seems to be due to an elevated insulin secretion which increases the over all utilization of glucose by the peripheral tissues. The study of time course of hyperglycemic response following intravenous glucose tolerance tests performed at high body temperature further support the possibility of an increase in insulin secretion in dogs subjected to hyperthermia.