INCREASE IN INSULIN BINDING AND INHIBITION OF THE DECREASE IN THE PHOSPHOLIPID CONTENT OF HUMAN TERM PLACENTAL HOMOGENATES IN CULTURE BY THE SULFONYLUREA GLIPIZIDE

Term placental explants were cultivated for 48 hr without (control) an d with various concentrations of glipizide. Maximum binding of [I-125] -insulin in the control samples was decreased after 12 and 24 hr retur ning to initial values after 48 hr. In the presence of glipizide the b inding was generally higher, reaching 180% (557 and 1000 nmol/L) of th e corresponding control value (P < 0.01) after 48 hr owing to the pres ence of nearly 3-fold more (P < 0.05) receptors than in the untreated controls. Tissue cholesterol content was almost unaffected whereas bot h the phospholipid content and the corresponding phospholipid-to-chole sterol 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 affec ts placental insulin receptors and the phospholipid content of the tis sue.