NUTRIENT-UPTAKE BY THE HINDLIMB OF GROWING PIGS TREATED WITH PORCINE SOMATOTROPIN AND INSULIN

The shift in nutrient partitioning induced by porcine somatotropin (pS T) is accompanied by a decrease in insulin sensitivity for whole-body glucose uptake. The relative contribution of metabolic changes in the hindlimb was investigated in eight pigs (55 kg) that had received reco mbinant pST (120 mu g/kg) or excipient (control) for 7 d. Uptake of me tabolites by the hindlimb was measured under basal conditions and duri ng hyperinsulinemic-euglycemic clamps at low [14 ng/(kg.min)] and high [360 ng/(kg.min)] insulin infusion rates. Dextrose infusion rate requ ired to maintain euglycemia was used as an index of whole-body glucose uptake in response to exogenous insulin. Effects of pST on hindlimb a nd whole-body glucose uptake were evident only at physiological levels of insulin (basal and low insulin infusion rate). During the low rate of insulin infusion, dextrose infusion rate was 79% lower for pST-tre ated pigs and glucose uptake by the hindlimb was 59% lower compared wi th control pigs. The decrease in glucose uptake by the hindlimb was en tirely accounted for by the estimated reduction in glucose utilization by adipose tissue of the hindlimb. Glucose:oxygen quotients were redu ced during basal (57%) and low insulin infusion (63%) with pST treatme nt, indicating a change in the pattern of substrate utilization. This is consistent with the concept that pST directs nutrients away from ad ipose and towards muscle growth by altering the response of tissues to homeostatic signals such as insulin.