3-Methylcholanthrene-induced EROD activity and cytochrome P-450 in immune organs of carp (Cyprinus carpio).

In this study, at first, we determined the optimal assay conditions for Ethoxyresorufin-O-deethylase activity and cytochrome P450 contents in the liver and two immune organs (spleen and head kidney) of carp. The Km values of cytochrome P450 1A activity were identical in the three organs, demonstrating that the enzyme belongs to the same isoform. In a second step, we showed that carp contained endogenous cytochrome P450 and EROD activity in two immune organs like in liver. These enzyme activities can be induced in a dose dependent manner by 3-methylcholanthrene, a specific inducer of cytochrome P450 1A, in the three organs. These results suggest that spleen and head kidney, the important immune organs in teleost fish, may be implicated in biotransformation for a class of contaminants like polycyclic aromatic hydrocarbons. In future, we can study the interaction between immune system and biotransformation system in fish.