Effect of anaesthesia on insulin-induced hypoglycemia in rabbits

The aim of this study was to determine how anaesthetized rabbits survive much longer than awake rabbits after receiving an insulin overdose. Insulin appeared to act in both groups of rabbits because there was a prompt fall in circulating glucose, free fatty acids, and beta-hydroxybutyrate concentrations. Carbohydrate appeared to be the principal energy source for anaesthetized rabbits because their respiratory quotient approached unity. Although the fall in glycemia was similar in both groups of rabbits, the circulating lactate concentration rose only in the anaesthetized group. This rise in lactate in the initial 60 min after insulin was given could account for most of the fall in glycemia if the source of lactate was the glucose pool. The decline in hepatic glycogen was close to 100 mumol/g liver; this would account for about one-third of the total energy turnover and close to one-half of the measured glucose appearance in these anaesthetized rabbits. As judged from the rate of oxygen consumption, muscle glycogen seemed to supply two-thirds of the fuel to be oxidized in these rabbits. However, only one-third of the lactate released from muscle was first converted to glucose and the remainder was oxidized directly to CO2. Although insulin provided the metabolic setting for a rapid rate of glucose oxidation, this rate appeared to be diminished when the overall rate of oxygen consumption was lower during anaesthesia.