GnRH主动免疫对SD雄鼠下丘脑GnRH合成及性腺反馈系统的影响

Effects of Active Immunization against GnRH on the Hypothalamus GnRH Biosynthesis and Gonadal Feedback System in Sprague-Dawley Male Rats

探讨GnRH主动免疫对SD雄鼠下丘脑GnRH合成及性腺反馈系统的影响。36只SD雄鼠随机分为免疫组、手术去势组及对照组,免疫组于12周龄时初免,8周后加免。放免法测定血清抗体滴度、激素浓度及下丘脑正中隆起GnRH含量,实时荧光定量PCR分析下丘脑生殖相关基因mRNA的变化。结果显示,GnRH主动免疫后12只免疫鼠中11只血清GnRH抗体滴度显著升高,血清LH、FSH及T浓度显著降低(P<0.05),睾丸严重萎缩(免疫去势鼠)。与对照鼠相比,免疫去势显著降低下丘脑GnRH含量(P<0.01),且显著下调下丘脑雌激素α受体(ERα)、雄激素受体(AR)、Kiss-1、GPR54及GnRH的mRNA表达水平(P<0.05)。手术去势鼠除血清LH、FSH浓度及下丘脑ERα的mRAN表达水平显著高于对照鼠外(P<0.05),其余指标均与免疫去势鼠类似。结果首次表明,GnRH主动免疫抑制性腺负反馈调节作用及降低了下丘脑GnRH的合成。

To explore the effects of active immunization against GnRH on the hypothalamus Gn- RH biosynthesis and gonadal feedback regulation system in adult Sprague-Dawley （SD） rats. Thirty-six male adult SD rats at the age of 12 weeks were randomly allocated to three groups of 12 animals each. Briefly, 12 rats were immunized against GnRH with a booster vaccination 8 weeks later. 12 intact males and 12 castrated rats were not administrated and served as controls. The GnRH antibody titers and reproductive hormone levels in sera, and the content of GnRH in the median eminence were determined by radioimmunoassay （RIA）. The mRNA expressions of reproduction-related genes in the hypothalamus were quantified by real-time fluorescence quanti- tative PCR technique. Active immunization against GnRH significantly increased serum GnRH antibody titers in eleven of twelve immunized rats, reduced serum LH, FSH and testosterone to around or undetectable levels （P〈0.05）, and resulted in a subcutaneously atrophy of testes in these rats （immunocastrates）. Compared with intact controls, immunocastration of rats significantly reduced the content of GnRH in the median eminence and mRNA levels of androgen-receptor （AR）, estrogen receptor alpha （ERa）, kiss-l, GPR54 and GnRH in the hypothalamus （P〈0.05）. As to surgical rats, excepting the serum LH and FSH levels, and the hypothalamic ERa mRNA levels were significantly higher than those in intact rats, the remaining experimental pa- rameters were similar to those of immunocastrates. These data firstly indicate that the feedback regulations of gonads on the hypothalamus and the synthesis capacity of GnRH in the hypothala- mus are both suppressed by active immunization against GnRH.