Ionic requirements for intracellular pH regulation in rainbow trout hepatocytes

The ionic requirements for pH regulation in isolated rainbow trout (Salmo gairdneri) hepatocytes were determined by manipulation of intracellular pH (pHi; measured by the dimethyloxazolidinedione distribution technique) by NH4Cl prepulse and changes in external [CO2] in the presence and absence of various drugs and external ions. The presence of a Na+/H+(NH+4) exchange system is supported by the following results: 1) the rate of recovery from an acid load is decreased by amiloride (0.5 mM) or reduction of external [Na+]; 2) the rate of 22Na uptake is increased during recovery from an acid load, and this increase in amiloride sensitive. The presence of a Cl-/HCO3- exchange system is supported by the observations that 1) pHi is increased, and 2) rates of recovery of pHi from acid loading are enhanced, by exposure to 4-acetamido-4'-isothiocyanostilbene-2,2'-disulfonic acid (0.5 mM) and reductions in external [Cl-]. Further studies are required to determine the role of these exchange processes during physiological pHi perturbations.