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 of rat megakaryocytes was investigated by the whole-cell patch-clamp technique. 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 intracellular acidification by 20 mM sodium acetate enhanced the response. NH4Cl also inhibited the Ins(1,4,5)P3-induced oscillation. Sodium acetate had no effect on the InsP3-induced oscillation, but enhanced the guanosine 5'-[gamma-thio]triphosphate-induced response. These results indicate that pH(i) modulates the ATP-induced cellular response at least at two points.