COMPARISON OF THE SIGNAL-TRANSDUCTION PATHWAYS ACTIVATED BY GASTRIN IN ENTEROCHROMAFFIN-LIKE AND PARIETAL-CELLS

Background & Aims: Gastrin stimulates acid secretion from parietal cel ls and histamine release from enterochromaffin-like (ECL) cells throug h identical gastrin receptors, However, gastrin has been shown to have a trophic effect only on ECL cells. The aim of this study was to comp are gastrin-induced signal transduction pathways in the ECL and pariet al cells of Mastomys natalensis, an African rodent. Methods: Both ECL and parietal cells were isolated from the gastric mucosa of M. natalen sis, and intracellular signal transduction events in response to gastr in were investigated. Results: Gastrin elicited histamine release from ECL cells and acid secretion from parietal cells in association with enhanced inositol phospholipid turnover, Although gastrin increased [H -3]thymidine incorporation into ECL cells, it had no effect on parieta l cells. Moreover, tyrosine phosphorylation and activation of mitogen- activated protein (MAP) kinase as well as c-fos and c-jun gene express ion were augmented only in ECL cells. In addition, gastrin increased t he formation of guanosine triphosphate-Ras with a simultaneous decreas e in guanosine diphosphate-Ras levels in ECL but not in parietal cells . Conclusions: Although gastrin receptors are present in both ECL and parietal cells, they activate the Ras-MAP kinase pathway only in ECL c ells.