Insulin kinetics in metasomatotropic diabetes

Abstract

Insulin kinetics were studied in dogs with metasomatotropic diabetes that had been induced by administration of growth hormone. The duration of this severe diabetes was about 1 yr. One of the dogs had been under insulin treatment for about 1 mo, but three others had not received insulin. In the unanesthetized diabetic and control dogs, in the postabsorptive state following intravenous injection of 131I-insulin, the amount of labeled immunoreactive insulin (L-IRI) injected and the amount present in venous blood were determined as the radioactivity of the complex precipitated by addition of excess of anti-insulin serum and anti-gamma globulin serum. The metabolic clearance rate of L-IRI was not significantly different in the diabetic and normal dogs (13.1 ± 3.3 and 10.7 ± 1.6 ml/kg body weight/min, respectively); the difference in fractional rate of disappearance was also not significant (0.053 and 0.054 fraction/min, respectively). The volume of distribution of L-IRI was comparable to the expected volume of extracellular fluid. The mass rate of disappearance of unlabeled immunoreactive insulin (IRI) in the metasomatotropic diabetic dogs was about one-half normal, however, due to the lower serum IRI level. The diabetic and control dogs were in a steady state with respect to systemic serum insulin during the test; thus the rate of loss could be related to the basal systemic delivery of insulin. The sub-normal delivery of insulin was sufficient for maintenance of life over long periods in this diabetic state, although the physical condition of the diabetic dogs deteriorated slowly.