Fate of porcine and human insulin at the subcutaneous injection site. I. Degradation and absorption of insulins in the rat.

The plasma insulin and serum glucose levels were compared after the subcutaneous and intravenous administration of porcine and human insulin in rats. While no difference was observed in plasma insulin or serum glucose levels with either insulin after intravenous administration, the plasma insulin levels and hypoglycemic effects of human insulin were greater than those of porcine insulin after subcutaneous administration. At various time intervals, radioactivity in subcutaneous tissue was assayed for insulin and/or its metabolites by gel filtration. Using these data, the absorption and degradation rate constants of these substances were estimated according to a one-compartment model. The degradation rate constants of human insulin was approximately half of that for porcine insulin.