The ovarian regulation of ovulation in teleost fish
The ovarian regulation of ovulation in teleost fish
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DOI：
10.1023/a:1007765902327
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发表时间：
1997-12-01
影响因子：
2.9
通讯作者：
Garczynski, M
中科院分区：
文献类型：
--
作者：
Goetz, FW;Garczynski, M
排卵是指成熟卵母细胞从卵巢中的卵泡壁外壳中释放出来。这个过程需要卵母细胞与颗粒层分离、卵泡壁破裂以及卵母细胞通过破裂部位主动排出。对包括鱼类在内的各种脊椎动物的实验结果表明，这些过程的控制可能涉及许多卵巢调节剂的协同作用，包括蛋白酶、蛋白酶抑制剂、孕激素、类二十烷酸、儿茶酚胺和血管活性肽。我们使用两种硬骨鱼模型：溪鳟（Salvelinus fontinalis）和黄鲈（Perca flavescens）来研究鱼类排卵的机制和控制。使用消减 cDNA 克隆，从溪鳟鱼卵巢中分离出卵巢和排卵特异性 mRNA（“TOP”=鳟鱼排卵蛋白）家族。此前尚未在任何脊椎动物的卵巢中观察到这些 mRNA；然而，它们编码的蛋白质与一组称为抗白细胞蛋白酶的哺乳动物蛋白酶抑制剂具有显着的序列同源性。这些抑制剂已从几种哺乳动物粘膜组织中分离出来，其功能可能是保护粘膜内层免受浸润白细胞释放的蛋白酶的非特异性降解。 TOP mRNA 编码的卵巢蛋白现已通过使用针对重组 TOP 的抗体进行蛋白质印迹来表征。鉴于 TOP 与抗白细胞蛋白酶的相似性，TOP 的功能之一可能是在排卵时调节蛋白水解。在黄鲈中，成熟类固醇 17 α,20 β-二羟基-4-孕-3-酮 (17,20-PG) 可在体外刺激生发囊泡破裂和排卵。吲哚美辛（一种前列腺素内过氧化物合酶抑制剂）可以阻断排卵刺激。因此，17,20-PG 似乎是通过产生类二十烷酸发挥作用，而类二十烷酸很可能是主要前列腺素。这一假设得到了以下观察结果的进一步支持：(1) 阻止排卵的吲哚美辛水平与阻止卵巢中初级前列腺素合成的吲哚美辛水平之间存在直接相关性； (2) 吲哚美辛阻断与初级前列腺素的孵化可以恢复排卵； (3)用17,20-PG刺激的黄鲈卵泡在排卵时PGF水平升高； (4)卵巢中类固醇对PGF的刺激对17,20-PG具有特异性。最后，17,20-PG 刺激排卵和卵泡前列腺素合成需要卵泡外组织和其他卵泡壁层的密切相互作用。
Ovulation is the release of a mature oocyte from its follicle wall enclosure in the ovary. This process requires the separation of the oocyte from the granulosa layer, the rupture of the follicle wall and the active expulsion of the oocyte through the rupture site. Results of experiments on various vertebrates, including fish, have shown that the control of these processes may involve the cooperative action of a number of ovarian regulators including proteases, protease inhibitors, progestational steroids, eicosanoids, catecholamines and vasoactive peptides. We have used two teleost models, the brook trout (Salvelinus fontinalis) and the yellow perch (Perca flavescens) to study the mechanism and control of ovulation in fish. Using subtractive cDNA cloning, a family of ovarian and ovulation specific mRNAs ("TOPs" = trout ovulatory proteins) was isolated from the brook trout ovary. These mRNAs have not previously been observed in the ovary of any vertebrate species; however, the proteins they code for have significant sequence homology to a group of mammalian protease inhibitors called antileukoproteinases. These inhibitors have been isolated from several mammalian mucosal tissues and their function may be to protect the mucosal lining from nonspecific degradation by proteases released from infiltrating leukocytes. The ovarian proteins encoded by the TOP mRNAs have now been characterized by Western blotting using antibodies derived against recombinant TOPs. Given the similarity of TOPs to antileukoproteinases, one function of TOPs may be to regulate proteolysis at the time of ovulation. In yellow perch, the maturational steroid, 17 alpha,20 beta-dihydroxy-4-pregnen-3-one (17,20-PG), stimulates both germinal vesicle breakdown and ovulation in vitro. The stimulation of ovulation can be blocked by indomethacin, a prostaglandin endoperoxide synthase inhibitor. Thus, it appears that 17,20-PG acts through the production of an eicosanoid that is most likely a primary prostaglandin. This hypothesis is further supported by the observations that (1) a direct correlation exists between indomethacin levels that block ovulation and those that block primary prostaglandin synthesis in the ovary; (2) ovulation can be restored in indomethacin-blocked incubates with primary prostaglandins; (3) PGF levels increase at the time of ovulation in incubations of yellow perch follicles stimulated with 17,20-PG; and (4) the stimulation of PGF by steroids in the ovary is specific for 17,20-PG. Finally, 17,20-PG-stimulated ovulation and follicular prostaglandin synthesis requires the close interaction of extrafollicular tissue and other follicle wall layers.