SYNCHRONOUS, SUSTAINED OSCILLATION OF C-PEPTIDE AND INSULIN IN THE PLASMA OF FASTING MONKEYS*

Abstract

The previously reported synchronous oscillations in plasma glucose and insulin levels were studied to determine whether the phenomenon can be attributed to cyclic secretion or degradation of the hormone. Plasma C-peptide concentrations were measured in Macaca mulatta and found to cycle with the same period as plasma insulin, suggesting that the oscillations of insulin arise from changing secretion rather than degradation. The amplitude of C-peptide oscillation was 50% that of insulin. Assuming 1st order kinetics and the same relative rates of disappearance as in humans, this difference in amplitudes is consistent with equal secretion rates for the 2 peptides.