Acharjee A, Chaube R, Joy K P
Department of Zoology, Centre of Advanced Study, Banaras Hindu University, Varanasi 221005, India.
Department of Biotechnology, Cochin University of Science and Technology, Kochi 682022, India.
Gen Comp Endocrinol. 2017 Sep 15;251:66-73. doi: 10.1016/j.ygcen.2016.10.001. Epub 2016 Oct 5.
The commercial fish spawning inducer Ovaprim (OVP) containing a salmon gonadotropin-releasing hormone analogue and domperidone (a dopamine receptor-2 antagonist) has been widely used as an effective spawning inducer in artificial breeding of fishes. It induces a preovulatory LH surge resulting in final oocyte maturation (FOM) and ovulation through a mechanism involving a steroidogenic shift to secrete a maturation-inducing steroid (MIS). In the present study, a 0.5μL/g body weight dose of OVP each injected at 0h and 24h intraperitoneally into gravid female catfish, Heteropneustes fossilis resulted in periovulatory changes in gonadotropin (GtH) subunit gene expression and steroid hormone levels. The OVP injections induced ovulation time-dependently from 6h onwards with 100% ovulation recorded from 24h to 48h. The fertilization rate was high from 6h to 18h and declined from 24h onwards. The OVP treatment up regulated the expression of GtH subunit genes differentially. The expression of glycoprotein-α (GPα) and luteinizing hormone (LHβ) peaked at 6h and 12h, and declined at 18h and 24h after the first injection. The second OVP injection at 24h elicited only a transient increase in the GPα expression at 6h and a sustained increase in the LHβ expression from 6h to 18h after the second injection, but both transcripts decreased subsequently. The follicle-stimulating hormone (FSHβ) expression responded to the OVP treatment from 12h onwards and maintained a constant level from 18h to 36h after the first injection; the second dose had little effect. Plasma steroids were differentially altered: the levels of estradiol-17β decreased while that of the MIS 17,20β-dihydroxy-4-pregnen-3-one; 17,20β-DP increased, causing the steroidogenic shift preceding FOM and ovulation. The present results indicate that LHβ expression coincides with the ovulation response and the late induction and maintenance of the FSH expression may be related to post-ovulatory events in the ovary.
商业用鱼类产卵诱导剂Ovaprim（OVP）含有鲑鱼促性腺激素释放激素类似物和多潘立酮（一种多巴胺受体-2拮抗剂），已被广泛用作鱼类人工繁殖中的有效产卵诱导剂。它通过一种涉及类固醇生成转变以分泌成熟诱导类固醇（MIS）的机制，诱导排卵前促黄体生成素（LH）激增，从而导致最终卵母细胞成熟（FOM）和排卵。在本研究中，以0.5μL/g体重的剂量在0小时和24小时分别腹腔注射到怀孕的雌性鲶鱼（印度胡鲶）体内，导致促性腺激素（GtH）亚基基因表达和类固醇激素水平出现排卵前变化。OVP注射从6小时起随时间依赖性地诱导排卵，24小时至48小时记录到100%排卵。受精率在6小时至18小时较高，从24小时起下降。OVP处理差异上调了GtH亚基基因的表达。糖蛋白-α（GPα）和促黄体生成素（LHβ）的表达在第一次注射后6小时和12小时达到峰值，在18小时和24小时下降。24小时的第二次OVP注射仅在6小时引起GPα表达的短暂增加，在第二次注射后6小时至18小时引起LHβ表达的持续增加，但随后两种转录本均下降。促卵泡激素（FSHβ）表达从12小时起对OVP处理有反应，在第一次注射后18小时至36小时维持恒定水平；第二次注射影响不大。血浆类固醇有不同变化：雌二醇-17β水平下降，而MIS 17,20β-二羟基-4-孕烯-3-酮（17,20β-DP）水平升高，导致FOM和排卵前的类固醇生成转变。目前的结果表明，LHβ表达与排卵反应一致，FSH表达的后期诱导和维持可能与卵巢排卵后事件有关。
