Comparison of the signal transduction pathways activated by gastrin in enterochromaffin-like and parietal cells

Background & Aims: Gastrin stimulates acid secretion from parietal cells and histamine release from enterochromaffin-like (ECL) cells through identical gastrin receptors, However, gastrin has been shown to have a trophic effect only on ECL cells. The aim of this study was to compare gastrin-induced signal transduction pathways in the ECL and parietal cells of Mastomys natalensis, an African rodent. Methods: Both ECL and parietal cells were isolated from the gastric mucosa of M. natalensis, and intracellular signal transduction events in response to gastrin 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 parietal cells. Moreover, tyrosine phosphorylation and activation of mitogen-activated protein (MAP) kinase as well as c-fos and c-jun gene expression were augmented only in ECL cells. In addition, gastrin increased the formation of guanosine triphosphate-Ras with a simultaneous decrease 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 cells.