Previous studies have implicated the nuclear progesterone receptor (Pgr or nPR) as being critical to ovulation in fishes. This study investigated the expression of Pgr in zebrafish ovarian follicles throughout development as well as putative downstream targets of Pgr by searching the promoter regions of selected genes for specific DNA sequences to which Pgr binds and acts as a transcription factor. Expression of Pgr mRNA increases dramatically as follicles grow and mature. In silico analysis of selected genes linked to ovulation showed that the prostaglandin receptors ptger4a and ptger4b contained the progesterone responsive element (PRE) GRCCGGA in their promoter regions. Studies using full-grown follicles incubated in vitro revealed that ptger4b was upregulated in response to 17,20β-P. Our studies also showed that the expression of phospholipase A2 (PLA2G4A) mRNA and protein, a key enzyme in prostaglandin synthesis, was upregulated in response to 17,20β-P treatment. pla2g4a was not found to contain a PRE, indicating that it is regulated indirectly by 17,20β-P or that it may contain an as-of-yet unidentified PRE in its promoter region. Collectively, these studies provide further evidence of the importance of Pgr during the periovulatory periods through its involvement in prostaglandin production and function by controlling expression of PLA2G4A and the receptor EP4b and that these genes appear to be regulated through the actions of 17,20β-P.

以前的研究表明核黄体酮受体（Pgr 或 nPR）对鱼类的排卵至关重要。本研究通过在选定基因的启动子区域中搜索 Pgr 结合并充当转录因子的特定 DNA 序列，调查了斑马鱼卵泡在整个发育过程中 Pgr 的表达以及 Pgr 的假定下游靶标。随着卵泡的生长和成熟，Pgr mRNA 的表达显着增加。对与排卵相关的选定基因的计算机分析表明，前列腺素受体ptger4a和ptger4b在其启动子区域中含有孕酮反应元件 (PRE) GRCCGGA 。使用培养的成熟卵泡进行的研究体外显示ptger4b响应17,20β-P而上调。我们的研究还表明，磷脂酶 A2 (PLA2G4A) mRNA 和蛋白质（前列腺素合成的关键酶）的表达在响应 17,20β-P 处理时上调。未发现pla2g4a包含 PRE，表明它受 17,20β-P 间接调节，或者它可能在其启动子区域中包含迄今为止尚未鉴定的 PRE。总的来说，这些研究通过控制 PLA2G4A 和受体 EP4b 的表达参与前列腺素的产生和功能，进一步证明了 Pgr 在排卵期的重要性，并且这些基因似乎是通过 17,20β-P 的作用来调节的。 .