来曲唑对豹纹鳃棘鲈提前性反转的诱导效果

Induction of Premature Reversal in Plectropomus leopardus by Letrozole

【目的】探究来曲唑诱导豹纹鳃棘鲈(Plectropomus leopardus)发生性反转的效果及性反转后性别相关基因的表达变化。【方法】取性腺已分化为II期卵巢的1龄豹纹鳃棘鲈,投喂含200 mg/kg来曲唑的饲料,分别在处理后45、90及120 d通过石蜡切片、HE染色检查性腺发育情况,统计生长指标及性反转比例,采用ELISA及实时定量PCR方法检测来曲唑处理120 d后对照组及处理组血清中11-酮基睾酮(11-Ketotestosterone,11-KT)含量和性腺中性别相关基因的相对表达量。【结果】来曲唑处理45 d时体长显著增长,处理90 d时体质量显著增长。90 d后的样本开始出现含少量精子细胞的间性性腺(55.56%),120 d时33.33%的实验鱼性腺发生性反转,出现大量精母细胞、精子细胞及精子及少量退化的卵母细胞。与对照组相比,处理后120 d性反转个体中血清中11-KT的浓度显著上升,性腺中dmrt1、cyp11b2及gsdf的表达显著高于对照组,cyp19a1a和foxl2的表达显著低于对照组。【结论】来曲唑可通过降低体内雌激素水平诱导性腺已分化为II期卵巢的豹纹鳃棘鲈性腺提前性反转为精巢。

【Objective】The aim of this study is to investigate the effects of letrozole on sex reversal in Plectropomus leopardus and the expression changes of sex-related genes after sex reversal.【Methods】One-year-old P.leopardus with stageⅡovaries were fed a diet supplemented with letrozole(200 mg/kg).On days 45,90 and 120 after treatment,the histological characteristics of the gonads were examined by HE staining,and the growth index and the proportion of fish with sexual reversal were counted.After 120 days of treatment,serum 11-ketotestosterone(11-KT)levels and the expression of sex-related genes in the gonads of the control and treatment groups were determined by ELISA and real-time quantitative PCR.【Results】A significant increase in body length occurred at 45 d of letrozole treatment and a significant increase in body mass occurred at 90 d of treatment.After 90 days of treatment,a small number of spermatozoa appeared in the gonads of the treatment group(55.56%).After 120 days of treatment,33.33%of the experimental fish in the treatment group had undergone sexual reversal,with a large number of spermatocytes,spermatozoa and sperm and a small number of degenerated oocytes present in the gonads.After 120 days of treatment,compared with the control group,the concentration of 11-KT was significantly increased in the serum of individuals with sexual reversal in the treatment group,the gonadal expression of dmrt1,cyp11b2 and gsdf was significantly upregulated,and the gonadal expression of cyp19a1a and foxl2 was significantly downregulated.【Conclusion】P.leopardus with stageⅡovaries can undergo sexual reversal to males by reducing endogenous estrogen levels with letrozole.