Inhibitory effects of synthetic rat C-peptide 1 on insulin secretion in the isolated perfused rat pancreas.

The effects of synthetic rat C-peptide 1 on insulin secretion from the isolated perfused rat pancreas was studied. The perfusion technique was according to the procedure described by Grodsky et al (1963) with a few modifications. After about 20 min of stabilization, the pancreas was perfused for 40 min with synthetic rat C-peptide 1 (100 ng/ml), during which (at 20 min) glucose concentration was switched from 2.7 to 16.6 mM. Insulin response to glucose (16.6 mM) was significantly decreased by the addition of the rat C-peptide 1 in advance when compared with those not pretreated with the C-peptide. In other experiments, the pancreas was exposed to glucose infusion (16.6 mM) for 60 min. 20 min after the start of glucose infusion, the C-peptide (100 ng/ml) was interposed for 20 min. The insulin secretion was reduced by the addition of the C-peptide. It is postulated that the C-peptide may have a role in the regulatory mechanism of the insulin secretion.