Regulation of intracellular pH by Ca2+ - activated proton channel

Background and aim: We have characterized a membrane current associated with a decrease in pHi, which can be induced by either elevating intracellular calcium or extracellular application of methylmercury (a potent agent in elevating intracellular Ca²⁺ concentration) in the alveolar macrophages bathing in the impermeant bilateral cesium aspartate solution.

Results: Decreasing pHi and elevating [Ca²⁺]i profoundly enhanced, but H-7 (a broad-spectrum kinase inhibitor), W-7 (a selective calmodulin antagonist) and KN-93 (a calmodulin kinase II inhibitor) inhibited the currents.

Conclusion: These results indicate that rat alveolar macrophages possess a calcium-activated and pHi-sensitive proton channel which can be phosphorylated and activated by calmodulin kinase II.