Effect of chlorpropamide treatment on insulin secretion in diabetics: Its relationship to the hypoglycemic effect

Abstract

We have studied the effect of chronic chlorpropamide treatment on insulin secretion in response to intravenous glucose. With treatment, the mean insulin level 5 min after glucose infusion increased significantly in 1 wk and reached its highest level in 1 mo. The increment over the fasting level increased similarly. The mean levels 20, 30, and 60 min after infusion did not change with treatment. All the diabetics, except one, with a fasting blood glucose level greater than 160 mg 100 ml had little or no insulin secretion 5 min after glucose infusion either before or during chlorpropamide treatment. The mean blood glucose levels decreased during treatment more in those with higher initial glucose levels. The increase in early (5 min) insulin secretion was not related to the hypoglycemic effect. These data indicate that with chlorpropamide treatment early insulin secretion usually improves. Since a decrease in blood glucose may occur without any change in insulin secretion in some patients, it is suggested that the improvement in early insulin secretion may be secondary to a general improvement in carbohydrate metabolism.