Epidermal growth factor modulates pepsinogen secretion in guinea pig gastric chief cells

Background and Aims: Although epidermal growth factor (EGF) inhibits gastric acid secretion, the effects it exerts on gastric chief cells are unknown. The aim of this study was to investigate whether EGF modulates pepsinogen release and intracellular Ca²⁺ concentrations ([Ca²⁺]i) and whether the effect involves mitogen-activated protein (MAP) kinase, eicosanoid generation, and nitric oxide. Methods: Chief cells were obtained by sequential digestion with collagenase and Ca²⁺ chelation. [Ca²⁺]i was measured in cells loaded with Fura2 and NO generation by the NO coproduct citrulline. Results: In situ hybridization, immunohistochemistry, and immunoblotting showed that EGF receptor and MAP kinases were constitutively expressed in chief cells. EGF caused a concentration-dependent stimulation of pepsinogen secretion and MAP kinase activity and determined a 2.5-7.0-fold increase in [Ca²⁺]i, inositol 1,4,5-tryphosphate, prostaglandin E₂, and leukotriene B₄. Tyrosine kinase inhibitors and cyclooxygenase and lipoxygenase inhibitors reduced pepsinogen secretion and eicosanoid generation induced by EGF. EGF increased citrulline generation and guanosine 3',5'-cyclic monophosphate accumulation sixfold; the effect was blocked by N(G) monomethyl-L-arginine, which is an NO synthase inhibitor. Conclusions: EGF stimulates pepsinogen secretion by activating eicosanoid generation, tyrosine kinases, MAP kinases, Ca²⁺, NO, and guanosine 3',5'-cyclic monophosphate.