IMMUNOHISTOCHEMICAL STUDY OF THE EXPRESSIONS OF EGF AND EGFR DURING TOLERANTION CYTOPROTECTION OF GASTRIC MUCOSA UNDER STRESS / 解放军医学杂志

ABSTRACT

SD rats were exposed to single or repeated water immersion restraint stress (WRS) for 4 h every other day for up to 6 days, during which the extent of gastric mucosal lesions was evaluated grossly and histologically. The expressions of EGF and EGFR in gastric mucosa were assayed by immunohistochemistry. The results showed that single exposure to WRS led to haemorrhagic lesions, but tolerance developed following repeated exposures to WRS. Histological evaluations showed that single exposure to stress conditions led to crater like haemorrhagic necrosis almost extending to the muscularis mucosae. The submucosa was apparently congestive and edematous. Following repeated WRS, however, mucosal haemorrhagic necrosis was significantly attenuated and submucosal edema and congestion apparently lessened. Active regeneration and proliferation of mucosal cells were observed at the same time. The expressions of EGF and EGFR could be detected in normal gastric mucosa. EGF was expressed in cytoplasma mainly in the regenerative zone with weaker expression at the basal portions of the gastric glands. EGFR was mainly distributed on the membrane of cells in the regenerative zone. Single WRS led to significant decreased in the expressions of EGF and EGFR. their expressions were absent in the necrotic region. After repeated WRS, enhanced expression of EGF and its receptors could be observed not only in mucosal cells of regenterative zone but also in other areas including the lumen of gastric glands. The results suggested that single WRS could cause severe gastric mucosal lesions, but gastric mucosa became tolerant to repeated WRS by way of toleration cytoprotection. Gastric adaptation was accompanied by active regeneration of mucosal cells mediated by EGF binding with its receptor, EGFR.