Resin acids, forming a major component of wood industry, cause numerous toxic effects on liver and red blood cells of fish.; Effect of dehydroabietic acid (DHAA) on erythrocyte pH of river lamprey was investigated using [C-14]DMO distribution to determine pH(i). Exposure of the cells to more than 200 mu M DHAA caused hemolysis within 10 min of incubation. Treatment with 50-200 mu M DHAA resulted in a rapid dose-dependent decrease in erythrocyte pH. DHAA-induced reduction of pH(i) was dependent on pH of the extracellular medium. Application of 100 mu M DHAA caused a 0.13 units drop of intracellular pH at pH(o) 8.0, 0.20 units at pH(o) 7.6, and 0.35 units at pH(o) 6.5. Cell pH was a saturable function of concentration of the uncharged form of DHAA (different concentrations of the uncharged form reached by varying of DHAA (total) concentrations and extracellular pH) with a rapid decline in pHi from 8.0 to 7.2 at 3-4 mu M concentration of the resin acid followed by modest pH(i) change at concentrations exceeding 10 mu M DHAA-induced acidification was reversible with pH, returning to control values in 15 min after removal of DHAA(o). The DHAA effect on cell pH was not due to inhibition of Na+/H+ exchanger. Two alternative mechanisms of DHAA action suggested are: alteration of membrane permeability to proton equivalents due to incorporation of DHAA into the lipid bilayer or carrier-like mode of penetration of the uncharged form of DHAA into the cell with the following dissociation. (C) 1998 Elsevier Science B.V. All rights reserved.