Initial and sustained calcium mobilizations in the parietal cell during stimulations with gastrin, inositol trisphosphate, phorbol ester and exogenous diacylglycerol.

Electron probe X-ray microanalysis revealed that cytoplasmic Ca2+ concentration increased in the restricted apical cytoplasm during stimulation of isolated guinea pig parietal cells with gastrin. Furthermore, this study, using 45Ca2+, aequorin and fura-2, revealed the mechanism involved in intracellular Ca2+ shifts caused by gastrin and the involvements of inositol 1,4,5-trisphosphate (IP3) and diacylglycerol in producing those shifts. The gastrin-mediated and IP3-sensitive Ca2+ pool was located in the smooth-surfaced membrane-enriched areas and released Ca2+ in the initial phase. Gastrin-mediated Ca2+ mobilization was also evoked by diacylglycerol, comprising an intracellular Ca2+ mobilization followed by a late, sustained and more localised Ca2+ entry from the extracellular space.