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 sodium and glucose uptake, glucose metabolism and Na+/K+-ATPase activity in isolated enterocytes of rats. Jejunal cells exposed to EGF had a significantly greater total uptake of sodium compared to controls after 6 min. Kinetic analysis of glucose transport across BBMV's demonstrated similar K-m values but a significant increase of the V-max in vesicles prepared from cells first exposed to EGF as compared to controls. EGF was also associated with a significant increase in glucose metabolism of jejunal enterocytes after 15 min. The activity of Na+/K+-ATPase increased in jejunal enterocytes exposed to EGF. The increase in Na+/K+-ATPase activity of the cells following EGF exposure was not accompanied by an increase in immunodetectable total or assembled Na+/K+-ATPase protein. EGF's effect on enzyme activity was abolished by removing NaCl from the incubation solution, and by preincubating the enterocytes with phlorizin prior to addition of EGF. Preincubation with amiloride did not inhibit the effect of EGF on Na+/K+-ATPase. The results confirm that EGF promotes uptake of both sodium and glucose by the jejunal mucosal cells, and suggest the effect of EGF on glucose and sodium is mediated through the brush-border membrane glucose-sodium transporter. The increase in Na+/K+-ATPase activity that occurs with EGF appears to be secondary to a rise in intracellular Na+ concentration. The short-term effects of EGF on glucose and sodium transport by the small intestine may have potential therapeutic implications.