Use of the hyperinsulinemic euglycemic clamp to assess insulin sensitivity in guinea pigs: dose response, partitioned glucose metabolism and species comparisons

The guinea pig is an alternate small animal model for the study of metabolism, including insulin sensitivity. However, only one study to date has reported the use of the hyperinsulinemic-euglycemic clamp (HEC) in anaesthetized animals in this species, and the dose-response has not been reported. We therefore characterized the dose-response curve for whole-body glucose uptake using recombinant human insulin in the adult guinea pig. Inter-species comparisons with published data showed species differences in maximal whole body responses (guinea pig human < rat < mouse), and the insulin concentrations at which half-maximal insulin responses occurred (guinea pig > human rat > mouse). In subsequent studies, we used concomitant D-[3-³H]-glucose infusion to characterize insulin sensitivities of whole body glucose uptake, utilization, production, storage and glycolysis in young adult guinea pigs at human insulin doses that produced ~half (7.5 mU.min^-1.kg^-1) and near-maximal whole body responses (30 mU.min^-1.kg^-1). Although human insulin infusion increased rates of glucose utilization (up to 68%) and storage, and at high concentrations increased rates of glycolysis in females, glucose production was only partially suppressed (~23%), even at high insulin doses. Fasting glucose, metabolic clearance of insulin and rates of glucose utilization, storage and production during insulin stimulation were higher in female than male guinea pigs (P<0.05), but insulin sensitivity of these and whole body glucose uptake did not differ between sexes. This study establishes a method for measuring partitioned glucose metabolism in chronically catheterized conscious guinea pigs, allowing studies of regulation of insulin sensitivity in this species.

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