Influence of environmental variables on the hepatic mixed-function oxidase system in bluegill sunfish, Lepomis macrochirus

Abstract

1. 1. MFO activity measured as 7-ethoxyresorufin O-deethylase (EROD) was assayed in hepatic microsomes of unfed bluegills acclimated to 4, 13, 18, or 26° C and injected once intraperitoneally with benzo(a)pyrene (BaP) at a dose of 1, 10 or 20 μg/g body weight. 2. 2. Fish acclimated to the higher temperature exhibited elevated EROD activity after the fifth day of injection; however, fish held at 4°C did not exhibit induction of this enzyme until 18 days following the initial injection and then only at the highest dose. 3. 3. Although the concentrations of BaP and metabolites in the liver 5 days after injection were similar for fish acclimated to three temperatures, EROD activities were greater for the fish acclimated to higher temperatures. 4. 4. Comparison of fed and unfed fish acclimated to 26°C revealed that at all doses higher concentrations of cytochromes P-450 and b 5 accumulated in hepatic tissue of fed fish; however, no difference was observed in EROD activities at any particular dose. 5. 5. The results of this work indicate that EROD activity increases as acclimation temperature and BaP dose increase.