Division of Fish Nutrition, Biochemistry and Physiology, Central Institute of Fisheries Education, Fisheries University Road, Versova, Mumbai, 400061, India,
Fish Physiol Biochem. 2013 Oct;39(5):1297-307. doi: 10.1007/s10695-013-9784-8. Epub 2013 Mar 17.
An experiment was conducted to study the effect of sub-lethal nitrite exposure on sex steroids (testosterone and estradiol), cortisol and thyroid hormones (T3 and T4) of Labeo rohita juveniles. Fishes previously fed with normal or elevated levels of vitamin E (VE) and tryptophan for 60 days were exposed to sub-lethal nitrite for another 45 days with same feeding regime. There were nine treatment groups, viz. VE0TRP0-N, VE0TRP0+N, VE100TRP0-N, VE100TRP0+N, VE100TRP0.75+N, VE100TRP1.5+N, VE150TRP0+N, VE300TRP0+N and VE200TRP1+N. Except the groups VE0TRP0-N and VE100TRP0-N, all other groups were exposed to nitrite. At the end of the 45 days of nitrite exposure, serum samples were assayed for sex steroids, cortisol and thyroid hormones. The serum T3 and T4 levels decreased to the extent of 84.5 and 94.06%, respectively, upon nitrite exposure. Dietary supplementation with additional amounts of VE and tryptophan appears to reduce the decline of the production of T4. The serum testosterone and estradiol decreased 97.31 and 92.86%, respectively, upon nitrite exposure. Supplementation with additional amounts of VE was found to reverse nitrite-induced inhibition of testosterone and estradiol production. Serum cortisol increased upon nitrite exposure and unexposed (VE100-N) group showed lower levels, which were comparable to groups fed with elevated levels of VE. The overall results of the present study revealed that environmental nitrites have a negative impact on steroidogenesis, which can be overcome by dietary supplementation of elevated amounts of VE (minimum of 150 mg VE Kg diet(-1)) and to a lesser extent by tryptophan (only at the level of 1.5% of the diet).
进行了一项实验，以研究亚致死浓度亚硝酸盐暴露对罗非鱼幼鱼的性激素（睾酮和雌二醇）、皮质醇和甲状腺激素（T3 和 T4）的影响。先前用正常或高浓度维生素 E（VE）和色氨酸喂养 60 天的鱼类，在用相同的喂养方案再暴露于亚致死浓度亚硝酸盐 45 天。有 9 个处理组，即 VE0TRP0-N、VE0TRP0+N、VE100TRP0-N、VE100TRP0+N、VE100TRP0.75+N、VE100TRP1.5+N、VE150TRP0+N、VE300TRP0+N 和 VE200TRP1+N。除了 VE0TRP0-N 和 VE100TRP0-N 组外，所有其他组均暴露于亚硝酸盐。在亚硝酸盐暴露的第 45 天结束时，测定血清中的性激素、皮质醇和甲状腺激素。血清 T3 和 T4 水平分别下降到 84.5%和 94.06%。额外补充 VE 和色氨酸似乎可以减少 T4 产量的下降。亚硝酸盐暴露后，血清睾酮和雌二醇分别下降了 97.31%和 92.86%。额外补充 VE 被发现可以逆转亚硝酸盐对睾酮和雌二醇产生的抑制作用。亚硝酸盐暴露后血清皮质醇增加，未暴露（VE100-N）组的水平较低，与高浓度 VE 喂养的组相当。本研究的总体结果表明，环境亚硝酸盐对类固醇生成有负面影响，可通过膳食补充高浓度 VE（最低 150mg VE Kg 饲料）和在一定程度上补充色氨酸（仅在饲料的 1.5%水平）来克服。
