Effects of growth hormone on the rate of disappearance of insulin from blood in depancreatized and Houssay dogs

Abstract

The rate of disappearance of an intravenous test dose of insulin was determined by assay of serum immunoreactive insulin (IRI) in depancreatized dogs. The test was repeated at intervals, in the same animals, before and during the administration of bovine growth hormone. Disappearance of IRI from serum was an exponential function of time from 15 to 120 minutes after the injection of insulin. The rate constant for insulin disappearance was not altered appreciably by injection of growth hormone (2 mg./Kg. of body weight/day) for 2 and 4 days. Similar results were obtained in a hypophysectomized-depancreatized dog given the same growth hormone treatment, but tested by intravenous injection of glucose together with a lesser dose of insulin. The test dose of insulin caused rapid and parallel decreases in serum free fatty acids and glucose. In the Houssay dog, injections of growth hormone raised the concentrations of free and esterified fatty acids to about three- and fourfold the control values, respectively. In intact dogs (prior studies), similar treatment with growth hormone increased serum IRI, five- to sevenfold, in the postabsorptive periods. Thus the results indicate that the rate of utilization of insulin in the body, which is dependent on serum insulin concentration, is greatly increased by growth hormone. The relations between hyperinsulinemia, and enhanced secretion and utilization of insulin, produced by growth hormone, are discussed.