Cytochrome P4501A responses in two tropical fish species, riverine catfish (Rita rita) and marine mudfish (Apocryptes bato).

The present study focuses on the establishment of methods for biomarker studies in freshwater and marine fish species as a basis for monitoring the extent of contamination of fisheries resources in tropical waters. Riverine catfish (Rita rita) and marine mudfish (Apocryptes bato) were given a single intraperitoneal injection with two selected inducing compounds; beta-naphthoflavone (BNF, 50 mg/kg) and a polychlorinated biphenyl mixture (Clophen A50, 20 mg/kg), and the heavy metal compound cadmium chloride (CdCl2, 1 mg/kg). Effects on cytochrome P4501A (CYP1A) were determined in post-mitochondrial supernatants (PMS) of liver at days 3 and 10 after treatment. EROD (7-ethoxyresorufin O-deethylase) activity and CYP1A protein level by indirect non-competitive enzyme-linked immunosorbent assay (ELISA) and Western blotting using a monoclonal antibody against fish CYP1A, were measured. BNF and Clophen A50 resulted in induction upto 9.5- and 5-fold, respectively, of CYP1A protein compared to control, while CdCl2 showed significant inhibition in these species. The present study examined the phase-I cytochrome P450 monooxygenase activity and response in these two tropical fish species for the first time.