Potential-induced changes in intracellular pH.

In a variety of cell types and tissues there is a strong dependence of intracellular pH (pHi) on membrane potential (Vm). Since cell Vm values can be altered by hormones, ion concentrations, and changes in membrane conductances, the potential-dependent changes in pHi may serve as an important mechanism by which cells can alter their pHi to an environmental stimulus. The H+ flux across the cell membranes is thought to take place via putative H+ channels that are blocked by low concentrations of divalent metal ions. However, in Na(+)-transporting epithelia, a major part of the H+ flux seems to be via the amiloride-sensitive apical Na+ channels, which are not sensitive to divalent metal ions. The H+ flux via the Na+ channels can be modulated by natriferic hormones and intracellular second messengers. The H(+)-conductive pathways may play an important role in signal transduction in some cells.