In Vitro Effects of Sulfonylurea on Glucose Transport and Translocation of Glucose Transporters in Adipocytes From Streptozocin-Induced Diabetic Rats

Abstract

The in vitro effects of the sulfonylurea glyburide on insulin binding and action were compared in adipocytes from control and nonketotic streptozocin-induced diabetic rats. Adipose tissue from control and diabetic animals was maintained in the absence or presence of 2 micrograms/ml glyburide for 20 h. Insulin binding and insulin-stimulated glucose transport were examined in adipocytes prepared from this tissue. As expected, insulin binding was increased in adipocytes from diabetic animals. Exposure of tissue to glyburide did not influence insulin binding in either control or diabetic cells. Glucose transport activity of diabetic cells, assessed with 2-deoxyglucose, was decreased 30-40% in both the absence (basal) and presence of insulin compared with controls. Glyburide potentiated insulin's effects in both control (15-20%) and diabetic (30-40%) adipocytes. As a result, glucose transport activity in glyburide-treated diabetic cells was restored to a level similar to that of control cells not exposed to the drug. The mechanism by which glyburide potentiated glucose transport activity was examined with the D-glucose-displaceable cytochalasin B-binding technique to measure glucose-transporter concentration in membranes prepared from control and diabetic adipocytes exposed to the drug. Adipocytes from this model of diabetes are known to have a decreased cellular content of glucose transporters. The concentration of glucose transporters was decreased by 31% in plasma membranes from insulin-treated diabetic cells. There were corresponding decreases in diabetic microsomal and total membrane fractions. There was also a 40% decrease in the translocation of transporters from the microsomes to the plasma membrane in response to insulin in diabetic cells.(ABSTRACT TRUNCATED AT 250 WORDS)