Effect of growth hormone on the response to insulin and glucose turnover in sheep

Abstract

SUMMARYThe hyperinsulinaemic euglycaemic clamp technique was used to determine the effect of recombinant bovine growth hormone on the response to insulin in castrate male Corriedale sheep. Saline or growth hormone (6·3 μg/min/animal) was infused into four sheep from the beginning of each experiment for 9 h, such that eight clamp experiments were performed, four with growth hormone and four controls. After a basal period of 3 h, insulin was sequentially infused at 1, 3 and then 6 mU/kg/min for 2 h each and the plasma glucose concentration was maintained at the value noted during the basal period by a variable rate of glucose infusion. Short-term growth hormone infusion decreased the glucose infusion rate (GIR) required to maintain eugylcaemia as well as the rates of glucose appearance and disappearance. The glucose metabolic clearance rate (MCR) was also decreased by the growth hormone treatment at all rates of insulin infusion, the average decrease ranging between 20 and 30%. The insulin concentration causing half maximal stimulation of glucose MCR and GIR was unchanged by growth hormone treatment. Endogenous glucose production was not consistently affected by either the growth hormone or insulin treatments. The results of this experiment demonstrate that growth hormone decreases the responsiveness of peripheral tissues to insulin, possibly at a site beyond the receptor.