BIOTRANSFORMATION ENZYME-ACTIVITIES IN THE OLFACTORY ORGAN OF RAINBOW-TROUT (ONCORHYNCHUS-MYKISS) - IMMUNOCYTOCHEMICAL LOCALIZATION OF CYTOCHROME P4501A1 AND ITS INDUCTION BY BETA-NAPHTHOFLAVONE

Olfaction is a crucial function in most fish species, but little is kn own about biotransformation enzymes in the olfactory organ. This study demonstrates that biotransformation enzymes usually found in the rain bow trout liver, are present in the olfactory organ as well. While mic rosomal cytochrome P450 reductase, p-nitrophenol hydroxylase and cytos olic glutathione S-transferase presented similar levels in both the ol factory organ and the liver, microsomal 7-ethoxyresorufin O-deethylase (EROD), 7-ethoxycoumarin O-deethylase, and 7-pentoxyresorufin O-deeth ylase were much lower in the olfactory organ (77-, 35-, 200-times resp ectively). Furthermore, microsomes from the olfactory organ were able to perform testosterone hydroxylation only in the 16 alpha-position wh ile testosterone was hydroxylated in the 16 beta-position by liver mic rosomes. Using polyclonal antibodies raised against perch cytochrome P 4501A1, the immunoreactive protein was shown to be strongly expressed in various cellular types forming the nonsensory epithelium. Some immu nostaining was also reported in the nonsensory cellular elements const ituting the sensory epithelium, while olfactory receptor cells failed to show cytochrome P4501A1 -immunoreactivity. Finally, the exposure of rainbow trout to waterborne beta-naphthoflavone (0.1 mu g ml(-1)) for 2 or 4 days resulted in a higher induction of EROD activity in the ol factory organ compared to the liver. The presence of biotransformation enzymes in the olfactory organ of rainbow trout addresses the questio n of their involvement in the detoxication/toxication of pollutants as well as in the olfactory function.