Combined effect of tributyltin and benzo[a] pyrene on the levels of sex hormone and vitellogenin in female Sebastiscus marmoratus

Tributyltin(TBT), an organometal used as an antifouling biocide, has b een reported to induce masculinization of fish. Benzo[a]pyrene(BaP), a widesprea d carcinogenic polycyclic aromatic hydrocarbon, has been reported that its micro somal metabolites can produce an estrogenic response when tested in vitro. This study was therefore designed to examine the potential in vivo influence of TBT, BaP and their mixture on sex hormone levels in serum of Sebastiscus marmoratus, which were given 2 separate intraperitoneally(ip) injections(a single injection every 7 d) of TBT(0.5, 1, 5 and 10 mg/kg), BaP(0.5, 1, 5 and 10 mg/kg), or both in combination(0.5, 1, 5 and 10 mg/kg); control fish received olive oil vehicle only. Six days after the 2nd injection, serum samples were collected and analyz ed for sex hormone levels and alkali labile protein phosphorus(ALPP), which is r elated to the yolk precursor protein vitellogenin. The pollutants at all doses s ignificantly reduced serum testosterone, estradiol and ALPP content after 2 inje ctions compared with the corresponding controls. The reduction of the estradiol levels should be response for the decrease of the vitellogenin levels. The resul ts in the present study suggested that aromatase seems not the major target acte d by TBT and BaP in fish. This study demonstrated that TBT or BaP exposure both inhibit the reproductive potential in female Sebastiscus marmoratus. Combined ef fect of TBT and BaP on the serum testosterone, estradiol and ALPP was not antago nism from the anticipation.