Extractable Insulin Measured by Immuno-Chemical Assay: Effect of Tolbutamide∗†

The new method for immunochemical assay of extractable insulin from the pancreas described in this report is based on the change in binding of insulin-I131to insulin antibodies in the presence of varying quantities of unlabeled insulin. The method was used to study changes in extractable pancreatic insulin after administration of tolbutamide to normal mice. Although tolbutamide caused a sharp decline in blood sugar within 2 hours of administration, a consistent decrease of insulin in the pancreas was not observed.