Biphasic responses of amino[ 14C]pyrine accumulation and oxygen consumption were registered by gastrin stimulation in dispersed parietal cells from guinea pig gastric mucosa, and this was mimicked with the calcium ionophore A23187. The characteristics of these phases (first phase and second phase) were distinguished by the differences in the requirements of extracellular Ca 2+. The first phase evoked by gastrin or ionophore A23187 was independent of extracellular Ca 2+, whereas the second phase was not. In the first phase, fluorescence of a cytosolic Ca 2+ indicator (quin2-AM) increased with the stimulation of ionophore A23187 and carbamylcholine chloride in the presence of extracellular Ca 2+. In addition, an increase in cytosolic Ca 2+ induced by ionophore A23187, but not by carbamylcholine chloride was also observed in the absence of extracellular Ca 2+, suggesting that Ca 2+ pool(s) in parietal cells might be present in the intracellular organelle. Cytochalasin B and colchicine, but not oligomycin, could eliminate this cytosolic Ca 2+ increase induced by A23187 in a Ca 2+-free medium. On the other hand, in a Ca 2+-free medium, addition of ATP after pretreatment with digitonin could diminish the cytosolic Ca 2+ increase brought about by A23187. This was also observed with oligomycin-treated cells, but not with cytochalasin B-treated cells. Similarly, subcellular fractionation of a parietal cell which had been pretreated with cytochalasin B or colchicine in an intact cell system reduced the rate of ATP-dependent Ca 2+ uptake. These observations indicate that intracellular Ca 2+ transport in dispersed parietal cells may be regulated by the microtubular-microfilamentous system. In conclusion, this study demonstrates the possibility of the existence of intracellular Ca 2+ transport mediated by gastrin or ionophore A23187 and regulated by the microtubular-microfilamentous system in parietal cells.