SHORT-TERM EFFECT OF EPIDERMAL GROWTH FACTOR (EGF) ON SODIUM AND GLUCOSE COTRANSPORT OF ISOLATED JEJUNAL EPITHELIAL-CELLS

This study was undertaken to assess the short-term effects of EGF on s odium and glucose uptake, glucose metabolism and Na+/K+-ATPase activit y in isolated enterocytes of rats. Jejunal cells exposed to EGF had a significantly greater total uptake of sodium compared to controls afte r 6 min. Kinetic analysis of glucose transport across BBMV's demonstra ted similar K-m values but a significant increase of the V-max in vesi cles prepared from cells first exposed to EGF as compared to controls. EGF was also associated with a significant increase in glucose metabo lism of jejunal enterocytes after 15 min. The activity of Na+/K+-ATPas e increased in jejunal enterocytes exposed to EGF. The increase in Na/K+-ATPase activity of the cells following EGF exposure was not accomp anied by an increase in immunodetectable total or assembled Na+/K+-ATP ase protein. EGF's effect on enzyme activity was abolished by removing NaCl from the incubation solution, and by preincubating the enterocyt es with phlorizin prior to addition of EGF. Preincubation with amilori de did not inhibit the effect of EGF on Na+/K+-ATPase. The results con firm that EGF promotes uptake of both sodium and glucose by the jejuna l mucosal cells, and suggest the effect of EGF on glucose and sodium i s mediated through the brush-border membrane glucose-sodium transporte r. The increase in Na+/K+-ATPase activity that occurs with EGF appears to be secondary to a rise in intracellular Na+ concentration. The sho rt-term effects of EGF on glucose and sodium transport by the small in testine may have potential therapeutic implications.