Sulphonylureas in vitro do not alter insulin binding or insulin effect on amino acid transport in rat hepatocytes

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Abstract
The effects of four sulphonylureas (gliclazide, glibenclamide, chlorpropamide and glipizide) on insulin binding and insulin action were studied in vitro using primary cultured rat hepatocytes. Cells were cultured for 20 h in the absence or presence of the sulphonylurea. The binding of insulin to rat hepatocyte monolayers was not altered in cells previously exposed to gliclazide at 0.7, 7.0 or 70 μg/ml; and to glibenclamide, chlorpropamide, or glipizide at 0.1, 1.0 and 10 μg/ ml. Insulin-induced down regulation was not affected by a simultaneous exposure of hepatocyte monolayers to any of the four agents. The stimulatory effect of insulin on α-aminoisobutyric acid uptake by the cells was not modified following exposure to the drugs. These studies indicate that the sulphonylureas tested do not have a direct effect on insulin receptors in hepatocytes; and that, in vitro, they do not alter the post-receptor events involved in the insulin-induced stimulation of amino acid transport in these cells.