CYTOPLASMIC PH REGULATES ATP-INDUCED CA(2-DEPENDENT K+-CURRENT OSCILLATION IN RAT MEGAKARYOCYTES())

The effect of cytoplasmic pH (pH(i)) on ATP-induced Ca2+ oscillation o f rat megakaryocytes was investigated by the whole-cell patch-clamp te chnique. Megakaryocytes responded to extracellular ATP and showed the periodic activation of K+ channels, which reflects the oscillation in intracellular free Ca2+ concentration. Intracellular alkalinization by 20 mM NH4Cl resulted in inhibition of the oscillatory response, and i ntracellular acidification by 20 mM sodium acetate enhanced the respon se. NH4Cl also inhibited the Ins(1,4.5)P3-induced oscillation. Sodium acetate had no effect on the InsP3-induced oscillation, but enhanced t he guanosine 5'-[gamma-thio]triphosphate-induced response. These resul ts indicate that pH, modulates the ATP-induced cellular response at le ast at two points.