Influence of Fasting on Changes in Glucose Metabolism Induced by Growth Hormone Injection in the Normal Dog

Normal dogs were fasted four to eight days, then subjected to a regimen of bovine growth hormone (1 mg./kg. per day, intramuscularly) for an additional four to six days with fasting continued. Plasma glucose concentration, and the rate of release and uptake of circulating glucose (as measured with C-14-glucose), were not increased significantly by growth hormone. This contrasts with the increases seen in the normally-fed dog given growth hormone. Nevertheless, the growth hormone regimen produced very high plasma insulin levels (as measured by radioimmunoassay) in the long-fasted animals, and produced the usual resistance in these animals to the effects of administered insulin to enhance glucose uptake and diminish glucose release. Thus neither increased glucose turnover nor increased plasma glucose concentration is a required factor in the development of hyperinsulinemia and insulin resistance in the growth hormone-treated intact dog.