Regulation of intracellular pH in single rat zona glomerulosa cells

The cytosolic pH (pHi) regulation of rat adrenal zona glomerulosa (ZG) cells was studied using single-cell spectrofluorimetry. Basal pHi was similar for cells incubated in the absence or presence of the HCO3(-)-CO2 buffering system. In the absence of HCO3-, inhibition of the Na(+)-H+ exchanger by dimethylamiloride (DMA) or removal of extracellular Na+ produced substantial acidification of basal pHi. In the presence of HCO3-, neither maneuver affected basal pHi. However, removing extracellular Cl- produced a prompt alkalinization not observed in the absence of HCO3-. Alkalinizing mechanisms were examined by monitoring pHi recovery from an acid load imposed by the NH4Cl pulse technique. In the absence of HCO3-, Na+ removal or DMA addition blocked greater than 80% of pHi recovery. In the presence of HCO3-, 34% of the pHi recovery rate was inhibited by 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS), 34% by DMA, and 72% by Na+ removal plus DIDS. Therefore both Na(+)-H+ and anion exchangers are active in these cells, working independently to maintain basal pHi. In the absence of HCO3-, Na(+)-H+ exchange is principally responsible for pHi recovery from an acid load. In HCO(3-)-containing medium, such recovery is shared by Na(+)-H+ and Cl(-)-HCO3- exchange.