Inability of Resin Acid Exposure to Elevate EROD Activity in Rainbow Trout (Oncorhynchus mykiss)

Abstract The induction of mixed function oxygenase enzymes, including ethoxyresorufin-o-deethylase (EROD), has been reported in fish downstream of bleached kraft mills in both Scandinavia and Canada. The compound(s) responsible have not been identified. Several experiments were conducted to determine if resin acids can induce EROD activity in rainbow trout (Oncorhynchus mykiss). Interperitoneal injections (i.p.) of dehydroabietic and abietic acid (50 mg/kg) did not elevate EROD activity after 2, 4 or 10 days. Dehydroabietic acid i.p. at 500 mg/kg did not increase EROD activity after 4 days. A mixture of ten resin acids i.p. at 370 mg/kg or water borne exposure at 100 µg/L did not induce EROD after 4, 8, or 16 days. Rosin gum i.p. at 370 mg/kg also did not induce EROD. These results suggest that resin acids are not the compounds primarily responsible for EROD induction below bleached kraft pulp mills.