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The Effect of Glibenclamide on Insulin Receptors in Normal Man: Comparative Studies of Insulin Binding to Monocytes and Erythrocytes^*

Division of Endocrinology and Metabolism, Departments of Internal Medicine and Clinical Chemistry, County Hospital, Tage Hansens Gade 8000 Århus C, Denmark

Address requests for reprints to: Dr. Elisabeth Hjøllund, Medical Department III, County Hospital, Tage Hansensgade 2, DK 8000 Aarhus C, Denmark.

In vivo studies in noninsulin-dependent diabetic patients have indicated that sulphonylurea drugs have an extrapancreatic effect. To further elucidate the mechanisms of this action, we studied the effect of glibenclamide on in vivo and in vitro cellular insulin receptor binding in normal subjects. Oral administration of glibenclamide in dose of 2.5 mg/day increased insulin binding to monocytes by 70% (P < 0.001), in spite of increased postprandial serum insulin levels. This change in insulin receptor binding occurred in the absence of changes in diet or body weight. In contrast, glibenclamide had no stimulatory effect on in vivo insulin binding to erythrocytes. The in vitro studies with monocytes revealed a dose-related insulin receptor stimulatory effect of glibenclamide (P < 0.05), with a maximal effect of 20% above basal level. These data indicate that glibenclamide increases the insulin-binding ability of monocytes but not of erythrocytes. As the monocyte is judged a better model for studying insulin receptors on target cells than the erythrocyte, this effect may be reponsible, at least in part, for the extrapancreatic effect of sulphonylureas, which seem to be of major importance for their hypoglycemic effect in noninsulin-dependent diabetic patients.

^* This work was supported by grants from the Danish Medical Research Counsil, Landsforeningen for Sukkersyges Fond, Aarhus Universitets Forskningsfond, NOVO Fond, Nordisk Insulin Fond, and Fonden til Leegevidenskabend Fremme.

Received June 2, 1982.