Increase in insulin binding and inhibition of the decrease in the phospholipid content of human term placental homogenates in culture by the sulfonylurea glipizide

Abstract

Term placental explants were cultivated for 48 hr without (control) and with various concentrations of glipizide. Maximum binding of [ 125I]-insulin in the control samples was decreased after 12 and 24 hr returning to initial values after 48 hr. In the presence of glipizide the binding was generally higher, reaching 180% (557 and 1000 nmol L ) of the corresponding control value (P < 0.01) after 48 hr owing to the presence of nearly 3-fold more (P < 0.05) receptors than in the untreated controls. Tissue cholesterol content was almost unaffected whereas both the phospholipid content and the corresponding phospholipid-to-cholesterol ratios were markedly, and in a time-dependent manner, increased by glipizide as compared to the controls. This was due to decreasing cholesterol and phospholipid concentrations in the controls during the time of culture as compared to initial values, and also to unchanged levels in glipizide-treated cultures. We conclude that glipizide affects placental insulin receptors and the phospholipid content of the tissue.