GnRH对人工孪生处理母牛下丘脑－垂体－性腺轴的调控

HORMONAL REGULATION OF HYPOTHALAMIC-PITUITARY-OVARY AXIS BY GNRH IN BEEF COWS TREATED FOR ARTIFICIAL TWINNING

从农区黄牛群中选择２１头产后正常母牛，分比三组。组Ⅰ在产后发情周期第１７天注射孕马血清促性腺激素（ＰＭＳＧ），发情当天注射抗ＰＭＳＧ血清，配种时注射生理盐水。组Ⅱ和组Ⅲ的ＰＭＳＧ及其抗血清处理方法与组Ⅰ相同，但在配种时分别注射促性腺激素释放激素（ＧｎＲＨ）或其抗体。各组母牛在ＰＭＳＧ处理前安装颈静脉血管导管，每日间隔１５分钟收集血样，连续３小时。发情当天，间隔３０分钟收集血样，直至发情征兆消失。应用双重酶标免疫测定方法和酶联免疫吸咐测定方法，分别检测血清中ＧｎＲＨ、ＬＨ和Ｐ＿４（孕酮）水平。结果表明，（１）在结合应用ＰＭＳＧ及其抗体处理的母牛发情期间，外源ＧｎＲＨ可使外周血中ＧｎＲＨ和ＬＨ水平升高。用ＧｎＲＨ抗体中和内源ＧｎＲＨ，可使血中ＧｎＲＨ和ＬＨ的水平降低，并阻抑排卵。（２）在母牛排卵前，通过某种途径调控ＧｎＲＨ和ＬＨ的脉冲释放水平，可以提高母牛的超排效果，并有可能控制母牛的排卵数。（３）用ＰＭＳＧ及其抗体和ＧｎＲＨ超排处理的母牛，发情期间的ＧｎＲＨ在排卵前有多个脉冲释放峰，但ＬＨ只有一个脉冲释放峰，而且ＧｎＲＨ脉冲释放高峰出现的时间较ＬＨ峰早。（４）在配种后第８天检出的血清孕酮水平与排卵数呈强正相关?

Abstract A total of 21 postpartum cows with normal cycle were allocated to three groups. Cows in group Ⅰ wereadministered with pregnant mate's serum(PMSG) on the day of estrous cycle,with PMSG antisertum on the day ofthe second cstrus,and with normal saline as placebo one hour before the first AI (artificial insemination) Animalsin groiips Ⅱand Ⅲwere treated with PMSG and its antiserum as group Ⅰ ,and imtead of saline were given aninjection of gonadotropin releasing hormone ( GnRH ) for group Ⅱ and of anti-GnRH serum for group Ⅲrespectively. Blood samples were collected via indwelling jugular cannulae at 15 minute intervals for consecutive 3hours every day from the day of PMSG injection to the onset of estrus ,and then continued at 30 minute intervalsuntil the end of estrus.the levels of GnRH , lutcinizing hormone(LH ) and progesterone in peripheral blood weremeasured by methods of Double Enzyme-linked Immunoassay or coinpetitive enzyme-linked immunosorbent assay.The results showed as follow1) The levels of GnRH and LH in peripheral blood on the day of estrusinereased when exogenous GnRH was administered and deereased while anti-GnRH serum was given to cowssuperovulated with PMSG and its antiserum. Superovulation was also hindered in GnRHantiserum treated group.(2)the number of cows response to superovulation could be improved and the ovulation rate might be controlled viasome regulation ways of GnRH and/or LH pulsative seeretions before ovulation of cows.(3 )There were several GnRH surges and one LH surge before ‘ovulation during cstrous period of cows treated with PMSG,anti-PMSGserum and GnRH. The ptcovulatory GnRH surge occurred earlier than the preovulatory LH surge.(4 ) Theprogesterone measurement in peripheral blood on day 8 after AI may be applied to estimating the superovulationeffect and to diagnosing twin-pregnancy.(5 ) The levels of GnRH , LH and steroid hormones in blood of cowsinereased obviously,which suggests that PMSG acts on ovaries for steroid genesis firstly,and then on hypothalamus