Chouzouris T M, Dovolou E, Dafopoulos K, Georgoulias P, Vasileiou N G, Fthenakis G C, Anifandis G, Amiridis G S
Department of Obstetrics and Reproduction, Veterinary Faculty, University of Thessaly, Karditsa, Greece.
Department of Obstetrics and Gynecology, Faculty of Medicine, University of Thessaly, Larissa, Greece.
Theriogenology. 2016 Oct 1;86(6):1615-1621. doi: 10.1016/j.theriogenology.2016.05.022. Epub 2016 May 27.
Ghrelin, a known growth hormone (GH) secretagogue, alters gonadotropin secretion in many species. Our objectives were to study the effects of ghrelin, on GH, LH, FSH secretion, and on luteal function of the ensuing estrous cycle in cattle. The estrous cycles of eight heifers were synchronized with progesteron releasing intravaginal device, and ovulation was induced with GnRH. Eight animals were treated with 1.5 μg kg(-1) bovine ghrelin (group Ghr, n = 4) or saline (group C, n = 4). Starting with the first ghrelin injection, 13 blood samples were collected over a 4-hour period for the determination of ghrelin, GH, LH, and FSH concentration. Progesterone levels were measured in samples collected every other day after estrus expression. Data were analyzed by repeated measures of ANOVA followed by Bonferroni post hoc testing and t test. In group Ghr, ghrelin concentration increased significantly 15 minutes after the first injection and remained in elevated levels until the 90th minute after the last injection. At the time of third ghrelin injection, GH was significantly higher in the Ghr group compared with C (17.1 ± 1.3 vs. 2.6 ± 0.3 ng mL(-1), P < 0.0001). Similar differences were found for the next three samples collected 15, 30, and 60 minutes later; no difference was evident after 90 minutes. In group Ghr, the area under the curve for LH and FSH were significantly reduced compared with the ones of group C (266 ± 10.3 vs. 331.9 ± 7.3, P = 0.007 and 102.3 ± 2.0 vs. 134.9 ± 5.5, P < 0.005 for LH and FSH respectively). At particular time points the concentration of the two gonadotrophins in group Ghr was significantly lower than those of group C (15, 30, 45, 75, and 90 and 60, 75, 90, 120, and 150 minutes after GnRH administration for LH and FSH respectively). The duration of the following estrous cycle was shorter (P = 0.004) in group Ghr (19.0 ± 0.4 days) compared with C (21.8 ± 0.5 days). In days 4, 6, 8, 10, and 14, progesterone concentration was lower (P < 0.05) in group Ghr compared with C; similarly the progesterone area under the curve for group Ghr (113.1 ± 4.8) was suppressed (P = 0.007) compared with that of C (141 ± 4.8). These results imply that ghrelin acts on pituitary causing impaired response to the GnRH stimulus, and it is likely to affect luteinization of the cellular compartment of the preovulatory follicle, and/or to suppress steroidogenetic activity of the luteal cells.
胃饥饿素是一种已知的生长激素促分泌素，可改变多种物种的促性腺激素分泌。我们的目的是研究胃饥饿素对牛生长激素（GH）、促黄体生成素（LH）、促卵泡生成素（FSH）分泌以及随后发情周期黄体功能的影响。八头小母牛的发情周期通过释放孕酮的阴道内装置同步，并用促性腺激素释放激素（GnRH）诱导排卵。八只动物分别用1.5μg kg⁻¹牛胃饥饿素处理（Ghr组，n = 4）或生理盐水处理（C组，n = 4）。从第一次注射胃饥饿素开始，在4小时内采集13份血样，用于测定胃饥饿素、GH、LH和FSH浓度。在发情表现后每隔一天采集的样本中测量孕酮水平。数据通过重复测量方差分析，随后进行Bonferroni事后检验和t检验进行分析。在Ghr组中，第一次注射后15分钟胃饥饿素浓度显著升高，并一直保持在较高水平，直到最后一次注射后90分钟。在第三次注射胃饥饿素时，Ghr组的GH显著高于C组（17.1±1.3对2.6±0.3 ng mL⁻¹，P < 0.0001）。在随后15、30和60分钟采集的接下来三个样本中也发现了类似差异；90分钟后差异不明显。在Ghr组中，LH和FSH的曲线下面积与C组相比显著降低（分别为266±10.3对331.9±7.3，P = 0.007；102.3±2.0对134.9±5.5，LH和FSH的P < 0.005）。在特定时间点，Ghr组中两种促性腺激素的浓度显著低于C组（分别在GnRH给药后15、30、45、75和90分钟以及60、75、90、120和150分钟时的LH和FSH）。与C组（21.8±0.5天）相比，Ghr组（19.0±0.4天）随后发情周期的持续时间较短（P = 0.004）。在第4、6、8、10和14天，Ghr组的孕酮浓度低于C组（P < 0.05）；同样，Ghr组的孕酮曲线下面积（113.1±4.8）与C组（141±4.8）相比受到抑制（P = 0.007）。这些结果表明，胃饥饿素作用于垂体，导致对GnRH刺激的反应受损，并且可能影响排卵前卵泡细胞区的黄体化和/或抑制黄体细胞的类固醇生成活性。
