Acute exposure of jejunal mucosa to ethanol has been reported to produce a depression of transmural glucose transport across this organ in vitro and in vivo. In an attempt to understand the mechanism of action of ethanol on intestinal transport, in the present study we have investigated the effect of ethanol on glucose uptake by purified brush-border membrane vesicles of hamster jejunum. Ethanol, in concentrations found in man after moderate drinking (1-5% w/v), was found to depress glucose uptake by the brush-border membrane in a dose-dependent and time-dependent manner. Mannose was used to measure nonspecific uptake, and we found that the ethanol-induced depression of glucose uptake was not related to an alteration of the nonspecific uptake of this sugar. The inhibition of glucose uptake of the ethanol-treated membranes completely disappeared after repeated washing of the membranes with ethanol-free buffer. Accordingly, the ethanol-induced depression of glucose uptake was not the result of irreversible damage to membrane proteins but was related to a direct effect of ethanol on the brush-border membrane. On the basis of these findings, it is concluded that a direct interference with glucose translocation across the brush border plays an important role in the ethanol-induced depression of transmural jejunal glucose absorption.
Animals Biological Transport