THE EPIDERMAL GROWTH-FACTOR RECEPTOR (EGF-R) IS PRESENT ON THE BASOLATERAL, BUT NOT THE APICAL, SURFACE OF ENTEROCYTES IN THE HUMAN GASTROINTESTINAL-TRACT

Background-While it is clear that luminal epidermal growth factor (EGF ) stimulates repair of the damaged bowel, its significance in maintain ing normal gut growth remains uncertain. If EGF is important in mainta ining normal gut growth, the EGF receptor (EGF-R) should be present on the apical (luminal) surface in addition to the basolateral surface. Aims/Subjects/Methods-This study examined the distribution of the EGF- R in the epithelium throughout the human gastrointestinal tract using immunohistochemistry, electron microscopy, and western blotting of bru sh border preparations. Results-Immunostaining of the oesophagus showe d circumferential EGF-R positivity in the cells of the basal portions of the stratified squamous epithelium but surface cells were EGF-R neg ative. In the normal stomach, and colon, the receptor to the basolater al surface with the apical membranes being consistently negative. EGF- R positivity within the small intestine appeared to be almost entirely restricted to the proliferative (crypt) region. Western blotting demo nstrated a 170 kDa protein in whole tissue homogenates but not in the brush border vesicle preparations. Conclusions-As the EGF-R is located only on the basolateral surfaces in the normal adult gastrointestinal tract, the major role of luminal EGF is probably to stimulate repair rather than to maintain normal gut growth.