POTENTIAL-INDUCED CHANGES IN INTRACELLULAR PH

In a variety of cell types and tissues there is a strong dependence of intracellular pH (pH(i)) on membrane potential (V-m). Since cell V-m values can be altered by hormones, ion concentrations, and changes in membrane conductances, the potential-dependent changes in pH(i) may serve as an important mechanism by which cells can alter their pH(i) to an environmental stimulus. The H+ Aux 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+ channel 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.