AJP - Gastrointestinal and Liver Physiology, Vol 271, Issue 3 509-G515, Copyright © 1996 by American Physiological Society

ARTICLES

Effect of luminal epidermal growth factor on enterocyte glucose and proline transport

J. A. Hardin, J. K. Wong, C. I. Cheeseman and D. G. Gall
Health Sciences Centre, University of Calgary, Alberta, Canada.

The effect of luminal epidermal growth factor (EGF; 60 ng/ml) and tyrphostin-51 (TYR; 10 microM), a tyrosine kinase inhibitor, on rabbit jejunal brush-border and basolateral membrane transport was investigated. In separate experiments, the effect of EGF, EGF and TYR, or TYR alone was examined in in vivo loops. In addition, Na+ permeability in brush-border membrane vesicles (BBMV) and the effect of Ca2+ channel blockade on EGF-stimulated glucose uptake were examined. Luminal EGF significantly (P < 0.0001) increased the maximal rate of transport (Vmax) for glucose and proline uptake in BBMV. TYR and Ca2+ channel blockade completely abolished the EGF-induced increase in glucose transport and in the case of TYR resulted in a significant reduction in Vmax compared with controls (P < 0.0001). The Michaelis-Menten constant did not differ in any experimental group. EGF had no effect on brush-border Na+ permeability or basolateral membrane glucose transport. The findings indicate a role for EGF in the acute regulation of jejunal brush-border membrane nutrient uptake. Furthermore, 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 function.

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