Ionic requirements for intracellular pH regulation in rainbow trout hepatocytes

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Abstract
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+(NH4+) 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 acid load, and this increase is 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 pH1i 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.