Nishiyama Maki, Chiba Hiroaki, Uchida Katsuhisa, Shimotani Toyokazu, Nozaki Masumi
1 Sado Marine Biological Station, Faculty of Science, Niigata University, Tassha, Sado, Niigata 952-2135, Japan.
Zoolog Sci. 2013 Nov;30(11):967-74. doi: 10.2108/zsj.30.967.
The relationship between sex steroid hormone profiles in plasma and gonadal function in hagfish is poorly understood. In the present study, plasma concentrations of estradiol, testosterone, and progesterone were examined with respect to gonadal development, sexual differences, and possible function of atretic follicles in the brown hagfish, Paramyxine atami, using a time-resolved fluoroimmunoassay. Plasma concentrations of these three hormones were low in juveniles of both sexes. In females, plasma estradiol showed a significant correlation with ovarian development, with the highest concentrations in late vitellogenic adults. Plasma testosterone and progesterone also increased significantly in non-vitellogenic adult females; however, plasma testosterone showed no significant differences among adult females at different ovarian developments, while plasma progesterone was significantly lower in late vitellogenic adults than it was in non-vitellogenic adults. Vitellogenic females that possessed atretic follicles showed significantly lower concentrations of all three hormones than females that only possessed normal follicles. In males, no significant differences were found in plasma estradiol or testosterone levels among groups of different developmental stages of the testis, while plasma progesterone showed a clear inverse relationship with testicular development. Thus, differences were found in plasma sex steroid hormone profiles between male and female P. atami. Moreover, plasma estradiol showed a significant correlation with ovarian development, which suggests that estradiol is involved in the regulation of ovarian development. The present study also revealed that steroid hormone production was strongly suppressed in females that possessed atretic follicles in their ovaries.
七鳃鳗血浆中的性类固醇激素水平与性腺功能之间的关系尚不清楚。在本研究中，使用时间分辨荧光免疫分析法，检测了褐海七鳃鳗（Paramyxine atami）血浆中雌二醇、睾酮和孕酮的浓度，以研究性腺发育、性别差异以及闭锁卵泡的可能功能。这三种激素在两性幼体中的血浆浓度都很低。在雌性中，血浆雌二醇与卵巢发育呈显著相关，在卵黄生成后期的成年个体中浓度最高。非卵黄生成期的成年雌性血浆睾酮和孕酮也显著增加；然而，不同卵巢发育阶段的成年雌性血浆睾酮无显著差异，而卵黄生成后期的成年雌性血浆孕酮显著低于非卵黄生成期的成年雌性。拥有闭锁卵泡的卵黄生成期雌性所有三种激素的浓度均显著低于仅拥有正常卵泡的雌性。在雄性中，不同睾丸发育阶段的组间血浆雌二醇或睾酮水平无显著差异，而血浆孕酮与睾丸发育呈明显的负相关。因此，发现褐海七鳃鳗雌雄之间血浆性类固醇激素水平存在差异。此外，血浆雌二醇与卵巢发育呈显著相关，这表明雌二醇参与了卵巢发育的调节。本研究还表明，卵巢中拥有闭锁卵泡的雌性类固醇激素分泌受到强烈抑制。
