The measurement and validation of the nonsteady-state rates of C-peptide appearance in the dog.

In order to verify the calculation of nonsteady rates of secretion of C-peptide, dog C-peptide was infused into 5 normal conscious dogs at varying rates. Using the decay curve obtained following a preliminary injection of C-peptide in each animal, concentrations during the infusion, and mathematical deconvolution, the rate of appearance of the C-peptide was calculated. This rate was within 12% of the infusion rates, with 94% of the C-peptide infused recovered in the calculation. The metabolic clearance of C-peptide was calculated to be 10.1 +/- 1.0 ml/min following both its injection and constant infusion. In conclusion, within the limits of the errors determined, C-peptide and therefore insulin secretion can be calculated on a continuous basis under nonsteady-state conditions.