Department of Animal and Dairy Sciences, University of Wisconsin-Madison, Madison, WI, USA.
Eutheria Foundation, Cross Plains, WI, USA.
Biol Reprod. 2020 Dec 1;103(6):1217-1228. doi: 10.1093/biolre/ioaa167.
Studying selection of multiple dominant follicles (DFs) in monovulatory species can advance our understanding of mechanisms regulating selection of single or multiple DFs. Carriers of the bovine high fecundity Trio allele select multiple DFs, whereas half-sib noncarriers select a single DF. This study compared follicle selection during endogenous gonadotropin pulses versus during ablation of pulses with Acyline (GnRH antagonist) and luteinizing hormone (LH) action replaced with nonpulsatile human chorionic gonadotropin (hCG) treatment in Trio carriers (n = 28) versus noncarriers (n = 32). On Day 1.5 (Day 0 = ovulation), heifers were randomized: (1) Control, untreated; (2) Acyline, two i.m. doses (Days 1.5 and D3) of 3 μg/kg; (3) hCG, single i.m. dose of 50 IU hCG on Day 1.5 followed by daily doses of 100 IU; and (4) Acyline + hCG. Treatments with nonpulsatile hCG were designed to replace LH action in heifers treated with Acyline. Acyline treatment resulted in cessation of follicle growth on Day 3 with smaller (P < 0.0001) maximum follicle diameter in Trio carriers (6.6 ± 0.2 mm) than noncarriers (8.7 ± 0.4 mm). Replacement of LH action (hCG) reestablished follicle diameter deviation and maximum diameter of DFs in both genotypes (8.9 ± 0.3 mm and 13.1 ± 0.5 mm; P < 0.0001). Circulating follicle stimulating hormone (FSH) was greater in Acyline-treated than in controls. Finally, Acyline + hCG decreased (P < 0.0001) the number of DFs from 2.7 ± 0.2 to 1.3 ± 0.2 in Trio carriers, with most heifers having only one DF. This demonstrates the necessity for LH in acquisition of dominance in Trio carriers (6.5 mm) and noncarriers (8.5 mm) and provides evidence for a role of GnRH-induced FSH/LH pulses in selection of multiple DFs in Trio carriers and possibly other physiologic situations with increased ovulation rate.
研究单排卵物种中多个优势卵泡（DF）的选择可以增进我们对调节单个或多个 DF 选择的机制的理解。携带牛高产仔 Trio 等位基因的个体选择多个 DF，而半同胞非携带者选择一个 DF。本研究比较了内源性促性腺激素脉冲期间和用 Acyline（ GnRH 拮抗剂）消融脉冲期间以及用非脉冲性人绒毛膜促性腺激素（ hCG）替代 LH 作用进行治疗时的卵泡选择，在 Trio 携带者（n=28）与非携带者（n=32）中进行。在第 1.5 天（第 0 天=排卵），小母牛随机分为：（1）对照，未处理；（2）Acyline，两次肌内注射（第 1.5 天和第 3 天）剂量为 3μg/kg；（3）hCG，第 1.5 天单次肌内注射 50IU hCG，然后每天注射 100IU；（4）Acyline+hCG。非脉冲性 hCG 处理旨在替代 Acyline 处理的小母牛中的 LH 作用。Acyline 处理导致第 3 天卵泡生长停止，Trio 携带者（6.6±0.2mm）的最大卵泡直径较小（P<0.0001），而非携带者（8.7±0.4mm）。LH 作用的替代（hCG）重建了两种基因型的卵泡直径偏差和 DF 的最大直径（8.9±0.3mm 和 13.1±0.5mm；P<0.0001）。循环卵泡刺激素（FSH）在 Acyline 处理组中高于对照组。最后，Acyline+hCG 使 Trio 携带者的 DF 数量从 2.7±0.2 减少到 1.3±0.2（P<0.0001），大多数小母牛只有一个 DF。这表明 LH 在 Trio 携带者（6.5mm）和非携带者（8.5mm）中获得优势的必要性，并为 GnRH 诱导的 FSH/LH 脉冲在 Trio 携带者和可能其他排卵率增加的生理情况下选择多个 DF 提供了证据。
