Rapid regulation of D-glucose transport in basolateral membrane of rat jejunum.

Abstract

D-Glucose transport and D-glucose inhibitable [3H]cytochalasin B binding to jejunal basolateral membrane vesicles were measured to investigate the possible association between changes in transport activity seen in hyperglycemia and density of transporter sites. Comparison was made between hyperglycemic animals, noninfused rats, and a group infused with sorbitol. Vascular infusion of D-glucose produced a rapid increase in D-glucose transport followed by a delayed and smaller increase in [3H]cytochalasin B binding. The Vmax for glucose uptake was increased after only 30 min of glucose infusion and continued to rise up to 6 h. Comparison with noninfused and sorbitol-infused controls showed that 2 h of glucose infusion produced a 3.5-fold increase in the Vmax for D-glucose uptake while D-glucose-inhibitable binding of [3H]cytochalasin B was unaffected. Six hours of hyperglycemia resulted in the further stimulation of glucose transport (4.1-fold) and a significant 1.8-fold increase in cytochalasin B binding over that for noninfused animals. Vesicles prepared from animals 4 h after an in vivo injection of cycloheximide showed an 80% reduction in glucose transport with no significant change in the cytochalasin B binding density. These results suggest that D-glucose transport in the basolateral membrane is regulated by a combination of a modulation of carriers already in the membrane and subsequent changes in carrier site density.