Pereira de Moraes Fabiane, Amaral D'Avila Camila, Caetano de Oliveira Fernando, Ávila de Castro Natália, Diniz Vieira Arnaldo, Schneider Augusto, Machado Pfeifer Luiz Francisco, Cantarelli Pegoraro Lígia Margareth, Ferreira Rogério, Germano Ferst Juliana, Tomazele Rovani Monique, Nunes Correa Márcio, Dias Gonçalves Paulo Bayard, Lucia Thomaz, Garziera Gasperin Bernardo
Graduate Program in Veterinary Medicine, Federal University of Pelotas, Capão do Leão, RS, Brazil.
Brazilian Agricultural Research Corporation, Porto Velho, RO, Brazil.
Theriogenology. 2021 Sep 1;171:30-37. doi: 10.1016/j.theriogenology.2021.05.008. Epub 2021 May 8.
Although prostaglandins are important in the ovulation process, a precise role for prostaglandin F2α (PGF) has not been elucidated. This study aimed to evaluate the regulation of PGF receptor mRNA (PTGFR) in granulosa cells and the local effect of PGF on ovulation and luteinization. In Experiment 1, using samples collected in vivo before (Day 2), during (Day 3) and after (Day 4) follicular deviation, expression of PTGFR in bovine granulosa cells was more abundant in the dominant follicle after deviation than in subordinates (P < 0.05). However, the expression of PTGFR was not regulated (P = 0.1) in preovulatory follicles at different time-points (0, 3, 6, 12 and 24 h) after ovulation induction with GnRH. In Experiment 2, to assess the role of systemic PGF treatment on luteinization and vascularization of preovulatory follicles, flunixin meglumine (FM), a nonsteroidal anti-inflammatory drug, was used to inhibit endogenous prostaglandin synthesis. Cows with preovulatory follicles were induced to ovulate with GnRH (0 h) and allocated to three groups: Control, with no further treatment; FM, treated with 2.2 mg/kg FM im 17 h after GnRH treatment; and FM + PGF, treated with FM 17 h after GnRH, followed by 25 mg dinoprost tromethamine (PGF) 23 h after GnRH treatment. FM injection was able to reduce the concentration of PGF in the follicular fluid (FF) (P < 0.001). However, contrary to our hypothesis, color Doppler ultrasound evaluations revealed decreased vascular flow in FM + PGF group (P < 0.05), and no effect of the treatments on intrafollicular P4 and E2 concentrations 24 h after GnRH. The prostaglandin metabolite (PGFM) concentrations in the FF were greater in cows receiving systemic PGF (P < 0.001), which prompted us to further check its role on ovulation. Therefore, in Experiment 3, in a final attempt to demonstrate the local effect of PGF on ovulation, cows with preovulatory follicles received an intrafollicular injection (IFI) of PBS (Control) or 100 ng/mL purified PGF (PGF group). PGF treatment did not affect the time of ovulation after IFI (66 ± 6.4 and 63 ± 8.5 h for control and PGF, respectively; P > 0.05), further suggesting that it has no direct effect in the ovulatory process. Based on our findings, we concluded that FM decreased PGF synthesis within the follicle, whereas PGF treatment decreased follicular vascularization. In addition, the in vivo model of intrafollicular injection evidenced that PGF alone is not able to locally induce ovulation.
尽管前列腺素在排卵过程中很重要，但前列腺素F2α（PGF）的确切作用尚未阐明。本研究旨在评估颗粒细胞中PGF受体mRNA（PTGFR）的调控情况以及PGF对排卵和黄体化的局部作用。在实验1中，使用在卵泡偏向之前（第2天）、期间（第3天）和之后（第4天）体内采集的样本，发现牛颗粒细胞中PTGFR的表达在卵泡偏向后的优势卵泡中比在从属卵泡中更丰富（P < 0.05）。然而，在用GnRH诱导排卵后的不同时间点（0、3、6、12和24小时），排卵前卵泡中PTGFR的表达未受调控（P = 0.1）。在实验2中，为了评估全身PGF治疗对排卵前卵泡黄体化和血管生成的作用，使用非甾体抗炎药氟尼辛葡甲胺（FM）抑制内源性前列腺素合成。对有排卵前卵泡的母牛用GnRH诱导排卵（0小时），并分为三组：对照组，不进行进一步处理；FM组，在GnRH处理后17小时肌肉注射2.2 mg/kg FM；FM + PGF组，在GnRH处理后17小时注射FM，随后在GnRH处理后23小时注射25 mg氯前列醇钠（PGF）。注射FM能够降低卵泡液（FF）中PGF的浓度（P < 0.001）。然而，与我们的假设相反，彩色多普勒超声评估显示FM + PGF组的血管血流减少（P < 0.05），并且这些处理对GnRH处理后24小时卵泡内P4和E2浓度没有影响。接受全身PGF的母牛卵泡液中前列腺素代谢物（PGFM）浓度更高（P < 0.001），这促使我们进一步检查其对排卵的作用。因此，在实验3中，为了最终证明PGF对排卵的局部作用，对有排卵前卵泡的母牛进行卵泡内注射（IFI），注射PBS（对照组）或100 ng/mL纯化的PGF（PGF组）。PGF处理不影响IFI后排卵时间（对照组和PGF组分别为66 ± 6.4小时和63 ± 8.5小时；P > 0.05），进一步表明其在排卵过程中没有直接作用。基于我们的研究结果，我们得出结论，FM降低了卵泡内PGF的合成，而PGF处理降低了卵泡血管生成。此外，卵泡内注射的体内模型证明单独的PGF不能局部诱导排卵。
