Effect Of Phenanthrene And 3-methylcholanthrene Exposure On Reproductive Functions Of Sebastiscus Marmoratus

This study was conducted to investigate the chronic effects of phenanthrene(Phe) and 3-methylcholanthrene(3MC) at environmental levels(0.06,0.6,6μg/L) on the reproductive function in an oceanic fish, Sebastiscus marmoratus.Some index on reporoductive function were assayed to examine the possible mechanism of the toxic effect.The different mechanism of low-rings and high-rings PAHs on the effects to reproductive function of teleost was compared.1.Metabolism of Phe and 3MC.After exposed to Phe for 50d,except for a significant increase was observed among the male fishes treated with 0.06μg/L Phe,there was no other significant alteration between control and exposed group on the hepatic EROD and GST activities.It is indicated that EROD and GST activities are no sensitive to Phe.3MC exposure induced the hepatic EROD activity,but the significant alteration in GST activity under 3MC exposure was not observed.2.The effect of Phe and 3MC on the transcription of CⅡGnRH. Significant transcriptional alterations in the brain of Sebastiscus marmoratus happened after exposure to Phe and 3MC.Phe exposure resulted in a dose-depend significant increase in CⅡGnRH mRNA levels among male fishes.In the female fishes,transcriptional levels of CⅡGnRH were induced by Phe,and the highest level was observed at 0.6μg/L group.A similar phenomenon was observed when Sebastiscus marmoratus was treated with 3MC.Low and medium concentration of 3MC exposure significantly induced the transcriptional levels of CⅡGnRH in brain,and the levels dropped when treated with high dose of 3MC.3.The effect of Phe and 3MC on the development of gonad.Phe and 3MC inhibited the ovarian GSI and spermatogenesis,17β-estradiol levels in gonad were inhibited after male and female fishes were exposed to Phe or 3MC foe 50d.The inhibition of 17β-estradiol may be responsible for the developmental delay of testis.The developmental delay of testis could be occurred under low concentrations of Phe or 3MC.The study unfolds a remarkable problem on the control of PAHs,and the results supply the theoretical basis for tbe reconsideration of environmental control criterion.Inhibition of 17β-estradiol under Phe or 3MC exposure may lead to the developmental delay of testis.It is indicated that 17β-estradiol play a crucial role to the development of gonad,including testis and ovary.The alteration of the gonadal development and reproductive functions mediated by Pbe or 3MC exposure may be mainly caused by the change of sexual steroid levels,which at the same time was regulated by CⅡGnRH expression.This study provides a thread for investigating the effects and mechanism of PAHs on the reproductive functions in teleost.