CYTOCHROMES P-4501A, P-4503A AND P-4502B IN LIVER AND HEART OF MUGIL CAPITO TREATED WITH CYP1A INDUCERS

Hepatic microsomes of Aroclor 1254-treated Mugil capito showed a singl e protein band detected in immunoblot with monoclonal antibody 1-12-3 to teleost (scup) CYP1A. The hepatic CYP1A like protein was induced wi th dose dependency after exposure of the fish to P-naphthoflavone (BNF ) as well as to Aroclor 1254. The induced mullet hepatic CYP1A protein was confined to a distinct fraction obtained by DE-52 anion exchange chromatography, and its relative content in that fraction increased in fish that were treated with higher doses of inducer. EROD (7-ethoxyre sorufin 0-deethylase) activity in hepatic microsomes from mullet treat ed with various doses of BNF correlated significantly (r(2) = 0.81502, P < 0.01) with CYP1A content. Treatment of the muller with low dose o f Aroclor 1254 125 mg/kg) induced only traces of CYP1A in liver micros omes (5.1 +/- 4.8 mg/kg). However, in muller treated with the high dos e of Aroclor 1254 (100 mg/kg) there was a dramatic induction in CYP1A content (408 +/- 275 pmol/mg) and this hemoprotein comprised about 83% of the total P-450 content of liver microsomes. The total level of P- 450, although induced in the liver tissue, was not induced in heart ti ssue of Aroclor 1254 treated mullet. On the other hand, P-4501A was in duced in treated muller to a level that comprised almost all of the ca rdiac P-450 content. EROD activity in the heart tissue of induced mull et was characterized by low V-max and high K-m values (K-m = 2.35 mM, V-max = 39.5 pmol/min per mg) compared to the values recorded for the enzyme from the liver (K-m = 1.0 mM, V-max = 288.0 pmol/min per mg). C ardiac CYP1A with low catalytic activity and repression of CYP-types o ther then CYP1A in heart of CYP1A induced fish may be part of a mechan ism aimed to preserve crucial levels of electron donors and molecular oxygen in cardiac muscle of fish exposed to CYPIA inducers. (C) 1998 E lsevier Science B.V. All rights reserved.