Insulin, ketones, glucose and glucagon: effects on the arterial basement membrane in vitro

The influence of insulin in physiological concentrations on basement membrane (BM)-like material from arterial smooth muscle cells was studied in cell cultures. BM-like material was isolated from the cell layer by a sonication-differential centrifugation technique after a 24-h incubation period with insulin and [3H]leucine added to the culture medium. Insulin in concentrations of 50, 100, 200 and 500 mU/l was found to exert no influence on incorporation of amino acids into BM-like material. Neither glucose, 16 mmol/l, ketones, 1 mmol/l, nor glucagon 100 ng/l were able to induce altered accumulation of BM-like material. The effect of insulin on the carbohydrate units of BM-like material was studied by concanavalin A-Sepharose chromatography of glycopeptides and by analyses of neutral hexoses and amino sugars. The result showed that insulin, 200 mU/l, induced a shift in composition of neutral sugars by decreasing the amount of galactose relative to glucose and mannose. No changes in glycopeptide binding to the concanavalin A-sepharose column were observed. The results indicate that insulin induces only minor alterations in BM-like material of arterial smooth muscle cells and that the changes apparently are restricted to the carbohydrate units.