Synchronous, sustained oscillation of C-peptide and insulin in the plasma of fasting monkeys.

The previously reported synchronous oscillations in plasma glucose and insulin levels have been further studied to determine whether the phenomenon can be attributed to cyclic secretion or degradation of the hormone. Plasma C-peptide concentrations were measured 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 percent that of insulin. Assuming first order kinetics and the same relative rates of disappearance as in humans, this difference in amplitudes in consistent with equal secretion rates for the two peptides.