皮质醇的周年变化与雌性虹鳟性腺成熟的关系

利用放射免疫分析法对饲养于恒定水温和自然光照下的雌性虹鳟血浆中皮质醇和性激素含量的周年变化进行了测定．结果表明：１）根据性腺结构指数和性激素分泌量判断，三龄时，雌性虹鳟达到性成熟；２）在血浆中不仅性激素而且皮质醇的变化水平与性腺结构指数的变化高度相关．排卵前性激素的水平都较高，伴随着排卵的进行性激素水平下降．而且在产卵季节虹鳟血浆中皮质醇水平也较高，三龄时皮质醇水平与性腺结构指数的相关系数为０．８６．这些结果提示，皮质醇在虹鳟的繁殖过程中可能发挥某种作用．

Relationship between Annual Change in Plasma Cortisol Levels and Gonadal Development in Female Rainbow Trout,Oncorhynchus mykiss

The present study showed plasma steroid hormone changes during the annual reprod uctive cycle of female rainbow trout under constant water temperature and natura l photoperiod. Female rainbow trout at three-year-old reached mature in their gonad. Changes in the plasma levels of both sex steroid hormones and cortisol we re highly correlated with those of GSI. Plasma levels of estradiol-17β and tes tosterone were highest in females sampled shortly before ovulation and declined in ovulated females, reaching lowest levels in postspawning fish. The concentrat ion of 17α, 20β- dihydroxy-4-pregnene-3-one rose markedly just before ovu lation and decreased after ovulation. Plasma cortisol level was high during spaw ning season and coefficient of plasma cortisol level with GSI was 0.86 at three-year-old fish. The results suggest that cortisol may exert s ome effects on reproduction of rainbow trout.