外源褪黑激素对水貂血清主要生殖激素年周期变化的影响

为探究埋植外源褪黑激素（MLT）对水貂血清主要生殖激素年周期变化的影响，实验选用4月龄雌貂和雄貂各72只，分为A、B、C、D组，A组（雌貂）和C组（雄貂）不做任何处理，B组（雌貂）和D组（雄貂）于2018年7月7日至2019年7月7日埋植外源MLT。实验期间，每隔30 d每组随机选取3只水貂，心脏采血并分离血清，共12次。用酶联免疫吸附实验（ELISA）法分别测定雌貂和雄貂血清中主要生殖激素含量。结果表明：（1） A组促性腺激素释放激素（GnRH）、催乳素（PRL）和孕酮（P）除冬季1月处于高水平，其他时间均处于较低水平；夏季在6月出现小高峰，P在7月出现小高峰；促卵泡素（FSH）和促黄体生成素（LH）在秋、冬季先下降后上升且在12月达高水平，春、夏季FSH呈逐渐下降趋势，LH呈先下降后上升趋势；雌二醇（E2）在秋、冬季逐渐上升且在1月达高水平，春、夏季逐渐下降后波动。（2） B组与A组相比较，GnRH分别在10月和1月显著升高（P ≤ 0.05），且1月极显著升高（P ≤ 0.01）；PRL在1月、2月、6月降低（P ≤ 0.05）；P在10月、6月升高（P ≤ 0.05），1月降低（P ≤ 0.01）；FSH和LH在10月显著上升（P ≤ 0.05），且FSH极显著上升（P ≤ 0.01），但FSH在1-2月降低（P ≤ 0.05），LH在3月显著上升（P ≤ 0.05）。（3） C组睾酮（T）仅在冬季1月上升至高水平；C组与D组相比较，T仅在1月降低（P ≤ 0.01）。由此得出，外源MLT能使1月GnRH浓度提高，PRL、P、T的浓度降低，使FSH和LH浓度于10月提前达峰值，E2于11月提前达峰值。埋植MLT导致雄性和雌性水貂发情时间不一致，因而此法并不适于种貂繁殖。

Melatonin implantation affected annual changes of main reproductive hormones in mink serum

The purpose of this experiment was to explore the effects of the implanted exogenous melatonin(MLT) on the annual changes of main reproductive hormones in mink serum.A total of 72 female and 72 male minks at 4 months old were randomly divided into four groups:Group A(female) and Group C(male) without any treatment as controls, Group B(female) and Group D(male) were implanted with exogenous MLT from July 7, 2018 to July 7, 2019.During the implantation period, three minks in each group were randomly selected to collect cardiac blood and separate serum samples for every 30 days, resulting in 12 sample collections.The Enzyme-linked immunosorbent assay(ELISA) was used to determine the contents of the main reproductive hormones in the collected sera.The results showed that (1) in Group A, the contents of gonadotropin-releasing hormone(GnRH), prolactin(PRL), and progesterone(P) were at higher levels in January than those in other time.The levels of PRL and P showed a small peak in June and July, respectively.Follicle stimulating hormone(FSH) and luteinizing hormone(LH) first decreased and then increased in autumn and winter and reached a high level in December.In spring and summer, FSH showed a gradual downward trend, while LH decreased at first and then increased.Estradiol(E2) gradually increased in autumn and winter and reached a high level in January, followed by a gradual decrease and fluctuated trends in spring and summer. (2) In Group B, in comparison with Group A, GnRH significantly increased in October(P ≤ 0.05) and January(P ≤ 0.01);PRL decreased in January, February, and June(P ≤ 0.05);P increased in October and June(P ≤ 0.05);FSH increased(P ≤ 0.01) in October, but decreased in both January and February(P ≤ 0.05);and LH significantly increased in March(P ≤ 0.05).(3) The testosterone(T) in Group C increased to the highest level only in January, while in Group D decreased in January(P ≤ 0.01).In summary, the exogenous MLT can increase the content of GnRH, reduce the concentrations of PRL, P and T in January, and induce FSH and LH to reach the peak in October and E2 to peak in November.Implantation of MLT resulted in inconsistent estrus periods between male and female minks, therefore this protocol is not suitable for mink breeding.