We studied the effects of dehydroabietic acid (DHAA), a major toxic resin acid in wood industry effluents, on cellular energetics in rainbow trout (Oncorhynchus mykiss) hepatocytes. In addition, the role of DHAA-induced change in intracellular Ca2+ in the energetic responses of the cells was evaluated. At sublytic concentrations, DHAA caused a reduction in cellular ATP content and a concomitant enhancement of glycolytic activity of the cells in a dose-dependent manner. No further decrease of cellular ATP content occurred after 60 min of DHAA-treatment indicating establishment of new energetic steady state in cells. DHAA also caused a rapid dose-dependent increase in oxygen consumption and in cellular heat production of the hepatocytes. The effect of DHAA on ATP content and glycolytic activity was independent from Ca2+, whereas, changes in oxygen consumption and heat production were Ca2+ – dependent. These results show that DHAA induces energetic imbalance in rainbow trout hepatocytes, which is apparently not due to direct interference of DHAA with ATP production nor does it seem to be caused by an indirect effect of elevated intracellular Ca2+ concentration on mitochondrial energetics. Therefore, the ATP depletion is likely due to increased cellular ATP consumption caused by amphiphilic action of DHAA on the cell membrane.

Introduction

Resin acids, like dehydroabietic acid (DHAA), are significant aquatic toxicants in wood industry effluents (Owens, 1991). Although they have been studied for some time the mechanisms of the toxic action of these compounds are still poorly known. Fish exposed to resin acid concentrations above 0.4 mg 1-1 develop jaundice, i.e. the endproduct of hemoglobin breakdown, bilirubin, accumulates in blood (Nikinmaa and Oikari, 1982; Mattsoff and Oikari, 1987). It appears that jaundice results as a consequence of both accelerated lysis of erythrocytes (Bushnell et al., 1985) and impaired excretion of bilirubin into bile (Mattsoff and Oikari, 1987; Mattsoff and Nikinmaa, 1988). Thus, disturbances of both erythrocyte and hepatocyte function occur during resin acid exposure.

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