Sulphonylureas and biguanides do not affect insulin binding in H35 hepatoma cells

Six sulphonylureas (tolbutamide, tolazamide, chlorpropamide, glibornuride, glipizide and gliquidone) and 2 biguanides (metformin and buformin) were tested for possible effects on insulin binding to H 35 rat hepatoma cells in culture. Insulin binding was measured after 24 and 72 hr of culturing cells in medium containing the drugs. Buformin and gliquidone were tested in concentrations from 10(-8)-5 X 10(-5) M, the other drugs in concentrations from 10(-7)-5 X 10(-4) M. All 24-hr experiments were repeated in cells down-regulated with 10 micrograms/ml insulin. None of the oral hypoglycemic agents tested had any significant influence on insulin binding to H 35 hepatoma cells, either in the presence or absence of insulin. We suggest that the insulin receptor status, at least in this type of liver cell, is not influenced by sulphonylureas or biguanides.