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Using human umbilical vein endothelial cells, and human microvascular endothelial cells from omental and subcutaneous fat obtained at laparotomy, we studied the effects of sulphonylureas and the biguanide metformin on endothelial cell proliferation, prostacyclin production, ecto-5'-nucleotidase activity, and von Willebrand factor release. Each drug produced a concentration-dependent proliferation of umbilical vein but not of microvascular endothelial cells. The stimulation of umbilical vein endothelial cell proliferation by sulphonylureas, but not by metformin, was serum- and insulin-dependent. Sulphonylureas and metformin had no effect on the proliferation of human dermal fibroblasts, smooth muscle cells derived from the umbilical artery, or 3T3 cells, until concentrations greater than 100 fold those found in vivo were reached, when there was inhibition of proliferation. These agents had no effect on prostacyclin or von Willebrand factor production, or on ecto-5'-nucleotidase activity, until high concentrations were used, at levels which also inhibited proliferation. The results suggest that the sulphonylureas and metformin, may, at concentrations found in vivo, induce changes in the turnover of endothelial cells from large vessels, but not of microvascular endothelial cells.

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