Glucose-galactose malabsorption: Demonstration of specific jejunal brush border membrane defect

Abstract

Jejunal brush border glucose transport was studied in a patient with glucose-galactose malabsorption and in controls, using jejunal brush border membrane vesicles (BBMV) prepared from conventional jejunal biopsies. Whereas BBMV from controls showed a seven-fold enhancement of D-glucose uptake in the presence of an inwardly directed sodium gradient compared with its absence, no such enhancement was seen in the patient's vesicles. In BBMV from the patient, initial D-glucose uptake under sodium gradient conditions was only 10% of the mean control value. In contrast, sodium/proton exchange in BBMV from the patient was intact. These data provide the first unequivocal evidence that the jejunal brush border membrane is the site ofa specific defect in sodium dependant glucose transport in glucose-galactose malabsorption. Measurement of glucose uptake by BBMV may well be the optimal diagnostic technique in this disorder.