EFFECTS OF TRIBUTYLTIN ON THE CYTOCHROME-P450 MONOOXYGENASE SYSTEM AND SEX STEROID-METABOLISM IN THE CLAM RUDITAPES DECUSSATA

The effects of tributyltin (TBT) on the cytochrome P450 monooxygenase system of the clam Ruditapes decussata have been Evaluated. Digestive gland microsomes were observed to catalyze the oxidative metabolism of testosterone. The metabolites detected were androstenedione, dihydrot estosterone, dihydroandrostenedione, 6 beta-, 6 alpha-, 2 alpha-, and 2 beta-hydroxytestosterone, estrone and 17 beta-estradiol. The effect of 0.1 and I mM TBT in the incubation mixture led to a significant red uction in the total metabolic rate and changes in the metabolite profi le. Clams were also exposed to different concentrations of TBT in wate r (0.1, 0.45, 2.27 mu g l(-1) of TBT as Sn) for seven days. A signific ant increase in testosterone levels was found in the TBT exposed organ isms. When digestive gland microsomes of control and exposed organisms were assayed for their ability to metabolize testosterone, a dose-res ponsive decrease in aromatization of testosterone to estrone and estra diol was observed (p<0.05). These changes indicated a significant inte raction of TBT with androgen metabolism in the darn Ruditapes decussat a and they may contribute to masculinization of clam physiology. (C) 1 998 Published by Elsevier Science Ltd. All rights reserved.