Intracellular pH regulation in hepatocytes isolated from three teleost species

The mechanisms of intracellular pH (pH(i)) regulation were studied in hepat ocytes isolated from three species of teleost: rainbow trout (Oncorhynchus mykiss), black bullhead (Ameiurus melas) and American eel (Anguilla rostrat a). Intracellular pH was monitored over time using the pH-sensitive fluores cent dye BCECF in response to acid loading under control conditions and in different experimental media containing either low Na+ or Cl- concentration s, the Na+-H+ exchanger blocker amiloride or the blocker of the V-type HC-A TPase, bafilomycin A(1). In trout and bullhead hepatocytes, recovery to an intracellular acid load occurred principally by way of a Na+-dependent amil oride-sensitive Na+-H+ exchanger In eel hepatocytes, the Na+-H+ exchanger d id not contribute to recovery to am acid load though evidence suggests that it is present on the cell membrane and participates in the maintenance of steady-state pH(i). The V-type H+-ATPase did not participate in recovery to an acid load in any species. A Cl--HCO3- exchanger may play a role in reco very to an acid load in eel hepatocytes by switching off and retaining base that would normally be tonically extruded. Thus, it is clear that hepatocy tes isolated from the three species are capable of regulating pH(i), princi pally by way of a Na+-H+ exchanger and a Cl--HCO3- exchanger, but do not ex ploit identical mechanisms for pH(i) recovery. J. Exp. Zool. 284:361-367, 1 999. (C) 1999 Wiley-Liss, Inc.