EVIDENCE FOR MITOCHONDRIAL METABOLISM OF 7,12-DIMETHYLBENZ(A)ANTHRACENE IN PORCINE OVARIES - COMPARISON WITH MICROSOMAL METABOLISM

7,12-dimethylbenz(a)anthracene (DMBA) causes necrosis in endocrine org ans. DMBA metabolism in follicles and corpora lutea from porcine ovari es was demonstrated not only in the microsomal but also in the mitocho ndrial fraction, in contrast to what has been found in the rat ovary. Maximal activities were present in these fractions of the corpus luteu m, with specific activities of 5.9 and 2.2 pmol/min x mg protein, resp ectively. DMBA metabolism in mitoplasts, i.e. mitochondrial inner memb ranes, proved to be more than 10-fold higher than the corresponding ac tivity in the mitochondrial fraction. The purities of the subcellular fractions were assessed by measurements of marker enzymes. 17-42% of t he mitochondrial DMBA metabolism was concluded to be due to microsomal contamination. In the mitoplast fraction such contamination was only 0.18-2.8%. Ellipticine and alpha-naphthoflavone reduced the metabolism of DMBA in the luteal microsomal fraction by 95 and 77%, respectively . In mitochondria the inhibition by these agents was 63 and 30%, respe ctively. Indomethacine and estradiol decreased microsomal DMBA metabol ism by 53 and 52%, respectively. In mitochondria the inhibition was 52 and 23%, respectively. None of these inhibitors affected the DMBA met abolism by the mitoplast fraction. (C) 1997 Elsevier Science Ireland L td.