Benzo[a]pyrene (B[a]P), as one of the typical polycyclic aromatic hydrocarbons and environmental contaminants, may cause endocrine disrupting effects and reproductive impairments in bivalves. However, the molecular mechanisms are still not fully understood. In this study, three reproductive stages (proliferative stage, growing stage and mature stage) of female scallops Chlamys farreri were exposed to B[a]P at 0, 0.38 and 3.8 μg/L. The present study determined the adverse effects of B[a]P on gonadosomatic index, circulating hormone concentrations, endocrine-associated gene expression and ovarian histology. Significant decrease in sex hormones including progesterone (P), testosterone (T) and 17β-estradiol (E2), was observed in B[a]P-treated C. farreri at growing stage and mature stage. These effects were associated with down-regulated expression of steroidogenic enzymes, including 3β-HSD, CYP17 and 17β-HSD, which were regulated by the upstream adenylate cyclase (Adcy) - protein kinase (PKA) signaling pathway. Ovarian transcript levels of estrogen receptor (ER) and caveolin-1 (cav-1) were decreased in B[a]P-treated C. farreri. Vitellogenin (Vtg), an estrogen-mediated gene involved in ovarian development, was down-regulated by B[a]P. Furthermore, ovarian histology was investigated to clarify the impairment of B[a]P on ovaries at growing stage and mature stage. Overall, the present results elucidated the anti-estrogenic mechanisms along the steroidogenic pathway and estrogen signaling pathway for the stage-dependent endocrine-disrupting effects of B[a]P. This finding provides important information regarding to the underlying molecular mechanisms of B[a]P-induced endocrine disruption in different reproductive stages of bivalves. In addition, the adverse effects should be taken into concertation during protection of bivalves germplasm resources and comprehensive evaluation of ecological risks.

中文翻译：

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苯并[a] py暴露通过雌性扇贝衣原体衣原体的类固醇生成途径和雌激素信号传导途径诱导生殖内分泌干扰作用。

苯并[a] py（B [a] P），作为典型的多环芳烃和环境污染物之一，可能会导致双壳类动物的内分泌干扰作用和生殖功能障碍。但是，分子机制仍未完全理解。在这项研究中，雌性扇贝衣原体的三个生殖阶段（增生期，生长期和成熟期）分别以0、0.38和3.8μg/ L的B [a] P暴露。本研究确定了B [a] P对性腺体指数，循环激素浓度，内分泌相关基因表达和卵巢组织学的不利影响。在成年期和成年期，经B [a] P处理的法氏梭状芽孢杆菌观察到性激素包括孕酮（P），睾丸激素（T）和17β-雌二醇（E2）的显着减少。这些作用与类固醇生成酶的表达下调有关，包括3β-HSD，CYP17和17β-HSD，它们受上游腺苷酸环化酶（Adcy）-蛋白激酶（PKA）信号通路的调节。在B [a] P处理的法氏梭菌中，雌激素受体（ER）和小窝蛋白1（cav-1）的卵巢转录水平降低。卵黄蛋白原（Vtg）是一种由雌激素介​​导的与卵巢发育有关的基因，被B [a] P下调。此外，对卵巢组织学进行了研究，以阐明B [a] P对卵巢在生长阶段和成熟阶段的损害。总体而言，目前的结果阐明了类固醇生成途径和雌激素信号传导途径对B [a] P的阶段依赖性内分泌干扰作用的抗雌激素机制。该发现提供了有关双壳类动物不同生殖阶段B [a] P诱导的内分泌破坏的潜在分子机制的重要信息。此外，在保护双壳类种质资源和综合评估生态风险时，应考虑到不利影响。