North Central Research and Outreach Center, University of Minnesota, Grand Rapids, 55744, United States.
Anim Reprod Sci. 2012 Jul;133(1-2):16-26. doi: 10.1016/j.anireprosci.2012.06.013. Epub 2012 Jun 23.
This experiment was conducted to determine the effect of altering preovulatory estradiol concentrations, through manipulation of length of proestrus, on peripheral progesterone concentrations, conceptus development, interferon tau (IFNT) production and uterine gene expression in cattle. Approximately 6 days after a time-synchronized ovulation, all antral follicles (≥5 mm) were ablated from the ovaries in beef heifers. To manipulate preovulatory estradiol concentrations, the length of proestrus prior to the GnRH-induced LH surge was altered between treatments. Heifers were administered PGF(2α) either -2.5 days (2.5 days of proestrus; HiE2; n=5) or -1.5 days (1.5 days of proestrus; LoE2; n=5) prior to GnRH (Day 0 of the experiment; 6.75 days after follicle ablation). Follicular dynamics and estradiol concentrations were evaluated during proestrus and progesterone concentrations were analyzed in the subsequent estrous cycle. On Day 7, embryos were transferred into all heifers using standard procedures. On Day 15.5 heifers were slaughtered, the reproductive tract was flushed to collect the conceptus and uterine flush media, and the uterine tissue was processed for subsequent analyses. Peripheral progesterone concentrations, conceptus development and IFNT production were similar between treatments. However, amount of nuclear progesterone receptor in the deep glandular epithelium and mRNA concentrations for estradiol receptor alpha (ESR1) in the uterine endometrium were less in the LoE2 than HiE2 treatment. These changes in uterine characteristics in heifers with lower preovulatory estradiol concentrations were not related to aspects of conceptus development monitored, however, it is speculated that the alterations in mRNA and receptor protein detected may contribute to pregnancy failure subsequent to day 15.5 of gestation.
这项实验旨在确定通过改变促性腺激素释放激素（GnRH）诱导的 LH 峰前的发情期长度来改变促排卵前雌二醇浓度对牛外周孕酮浓度、胚胎发育、干扰素 tau（IFNT）产生和子宫基因表达的影响。在同步排卵后约 6 天，从肉牛小母牛的卵巢中切除所有窦前卵泡（≥5mm）。为了操纵促排卵前雌二醇浓度，在 GnRH 诱导的 LH 峰前改变发情期的长度以改变处理之间的发情期长度。在 GnRH（实验的第 0 天；卵泡消融后 6.75 天）前，给小母牛注射 PGF(2α)，时间分别为 -2.5 天（发情期 2.5 天；高雌二醇；n=5）或-1.5 天（发情期 1.5 天；低雌二醇；n=5）。在发情期期间评估卵泡动态和雌二醇浓度，并且在随后的发情周期中分析孕酮浓度。在第 7 天，按照标准程序将胚胎转移到所有小母牛中。在第 15.5 天，将小母牛屠宰，冲洗生殖道以收集胚胎和子宫冲洗液，并处理子宫组织以进行后续分析。处理之间的外周孕酮浓度、胚胎发育和 IFNT 产生相似。然而，在低雌二醇组中，深部腺上皮中的核孕酮受体数量和子宫子宫内膜中的雌二醇受体 alpha（ESR1）mRNA 浓度在 LoE2 中比 HiE2 中少。发情期雌二醇浓度较低的小母牛的这些子宫特征的变化与监测的胚胎发育方面无关，但是推测检测到的 mRNA 和受体蛋白的改变可能导致妊娠失败在 15.5 天妊娠后。
