Involvement of multiple sodium ions in intestinal d-glucose transport.

Abstract

Brush border membrane vesicles isolated from rabbit small intestine were used to measure the interactions between Na and glucose transport with a rapid uptake technique. A plot of glucose uptake rate vs. increasing Na concentration yielded a sigmoid curve. Hill analysis revealed a coefficient of 1.9 .+-. 0.02 (.+-. SEM [standard error of the mean]), consistent with at least 2 Na involved in glucose transport. Transport coupling was then measured directly with double-label experiments in which the uptakes of D-glucose and Na were determined in the presence and absence of cotransported solute. At the earliest time point, the ratio of cosubstrate-dependent Na transport to glucose transport was 3.2 .+-. 0.7 (.+-. SEM). Two or more Na are apparently coupled to glucose transport across the intestinal brush border membranes.