Proximo‐distal gradient of Na+‐dependent D‐glucose transport activity in the brush border membrane vesicles from the human fetal small intestine

Abstract

Brush-border membrane vesicles were isolated from the jejunum and ileum of 17–20-week-old normal human fetuses and found to be highly enriched in sucrase activity with less than 5% contamination by basolateral membranes. Time course studies of D-glucose uptake clearly showed a transient, phlorizin-sensitive, and Na⁺-dependent accumulation of sugar into these vesicles. Higher maximum overshoot values and initial rates of D-glucose uptake were recorded in jejunal as compared to ileal vesicles while low substrate binding to the membranes, identical intravesicular volumes and equivalent dissipation of the Na⁺-gradient were found in the two preparations. It was concluded that a fully functional Na⁺-D-glucose cotransport system is present with a proximo-distal gradient of activity during the early gestation period.