Cytochalasin B-sensitive, sodium ion-dependent glucose transport in intestinal microvillous membrane

Abstract

It was found that sodium ion-dependent glucose uptake by microvillous membrane (MVM) vesicles was partially inhibited by cytochalasin B with a half-maximum inhibition at ca. 10 microM. The MVM was photolabeled with [3]cytochalasin B. The Kd value and the maximum number of binding sites for cytochalasin B were ca. 8 microM and 70 pmol/mg protein, respectively. SDS-PAGE of the photolabeled MVM revealed 2 binding components. One was 86 K in Mr and the other 42 K. The binding of cytochalasin B to the 86 K component was affected neither by cytochalasin E nor by the presence of 0.5 M NaCl, but was depressed in the presence of 2-deoxy-D-glucose or phlorizin, which had no effect on the labeling of the 42 K component. These and other data suggested that the 86 K component might be responsible for a cytochalasin B-sensitive glucose transport in intestinal epithelial MVM.