pHi controls cytoplasmic calcium in rat parotid cells

The goal of this investigation was to determine if cytoplasmic pH (pHi) modulated the basal level of the concentration of calcium ions in the cytoplasm (Cai) in rat parotid cells. We investigated the effects of various experimental manipulations on both pHi and Cai as measured with BCECF and the calcium photoprotein aequorin, respectively. We found that various experimental manipulations that increased pHi, such as exposure of the cells to NH4Cl, a decrease of the partial pressure of CO2 or an increase in extracellular pH in the presence of nigericin invariably increased Cai. Moreover, experimental manipulations which lowered Cai, such as a reduction of extracellular [NaHCO3] or the removal of loaded NH4 invariably decreased Cai. Thus pHi and Cai are directly related in parotid cells. Since recent studies have shown that Cai directly influences pHi, we suggest that Cai-handling and pHi-handling are tightly linked in parotid cells.