Background - While it is clear that luminal epidermal growth factor (EGF) stimulates repair of the damaged bowel, its significance in maintaining normal gut growth remains uncertain. If EGP3 is important in maintaining 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 brush border preparations. Results - Immunostaining of the oesophagus showed circumferential EGF-R positivity in the cells of the basal portions of the stratified squamous epithelium but surface cells were EGF-R negative. In the small intestine, and localised the normal stomach, colon, immunostaining receptor to the basolateral 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 demonstrated 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.
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