EFFECT OF LUMINAL EPIDERMAL GROWTH-FACTOR ON ENTEROCYTE GLUCOSE AND PROLINE TRANSPORT

The effect of luminal epidermal growth factor (EGF; 60 ng/ml) and tyrp hostin-51 (TYR; 10 mu M), a tyrosine kinase inhibitor, on rabbit jejun al brush-border and basolateral membrane transport was investigated. I n separate experiments,the effect of EGF, EGF and TYR, or TYR alone wa s examined in in vivo loops. In addition, Na+ permeability in brush-bo rder membrane vesicles (BBMV) and the effect of Ca2+ channel blockade on EGF-stimulated glucose uptake were examined. Luminal EGF significan tly (P < 0.0001) increased the maximal rate of transport (V-max) for g lucose and proline uptake in BBMV. TYR and Ca2+ channel blockade compl etely abolished the EGF-induced increase in glucose transport-and in t he case of TYR resulted in a significant reduction in V-max compared w ith controls (P < 0.0001). The Michaelis-Menten constant did not diffe r in any experimental group. EGF had no effect on brush-border Na+ per meability or basolateral membrane glucose transport. The findings indi cate a role for EGF in the acute regulation of jejunal brush-border me mbrane nutrient uptake. Further more, tyrosine kinase activity appears to be involved both in mediating EGF-induced alterations in transport function and in the maintenance of basal brush-border membrane functi on.