Blood glucose and plasma insulin levels during prolonged pentobarbitone anaesthesia in the rat

Experiments were conducted on 18 hr fasted male Wistar rats at 15 minutes (short-term anaesthetised) and 5 hr (long-term anaesthetised) after the induction of anaesthesia with sodium pentobarbitone, 45 mg/kg body weight intraperitoneally. Long-term anaesthetised animals received supplementary injections of anaesthetic, 10 mg/kg body weight at hourly intervals, or as required to maintain anaesthesia. Normal basal arterial blood glucose and plasma insulin levels were well maintained during 5 hours of anaesthesia. Following an intravenous glucose challenge, plasma insulin levels and insulin-glucose ratios were slightly reduced in the long-term anaesthetised animals, but glucose tolerance was not significantly impaired. The insulin secretory capacity of pancreas pieces isolated from short-term and long-term anaesthetised animals and incubated in vitro in the absence and presence of glucose was not significantly altered. The hypoglycaemic effect of an intravenous injection of insulin was markedly diminished and the rate of elimination of insulin from the circulation was significantly increased in the long-term anaesthetised animals. These observations indicate adjustments of the glucose homeostatic mechanism during prolonged pentobarbitone anaesthesia in fasting rats.