Efeito do eCG sobre parâmetros ovarianos e endometriais associado a protocolo hormonal de antecipação da ciclicidade em éguas.

Abstract

The objective of this study was to evaluate ovulatory and luteal characteristics, as well as uterine gene expression and endometrial morphology, in transitional mares that received equine chorionic gonadotropin (eCG) as part of a progesterone (P4)-based hCG ovulation induction protocol during late winter. In experiments I (n=23) and II (n=8), a total of 31 crossbred mares had an intravaginal P4 releasing device (2.0g) implanted for ten days. Following P4 device removal, follicular growth was monitored, with mares receiving either 500 IU of eCG (eCG Group) or 2.5 ml of saline solution (Control Group) once a dominant ovarian follicle (DF) had reached 30mm in diameter. In both groups, human chorionic gonadotropin (hCG; 2.000 IU) was administered as soon as an ovulatory follicle (OF)≥ 35mm in diameter, was detected. Ovarian ultrasonography was performed from the beginning of the protocol (D0) until 20 days post-ovulation. From days 3 to 20 post ovulation, ultrasound was performed using color doppler mode. P4 concentrations were assessed via chemiluminescence, and uterine biopsies were performed in order to assess expression of the ESR1, ESR2, PGR, and P19 genes, in addition to histopathological analyses. Intergroup data were compared using T tests with a significance level of P < 0.05. Follicular growth rates before (P=0.554) and after (P=0.257) P4 device removal, ovulation rate (P=0.193), time to ovulation (P=0.998), OF diameter at the time of ovulation (P=0.618), corpus luteum (CL) diameter at 10 days (P=0.751), 12 days (P=0.512), and 14 days (P=0.181) after ovulation, and serum P4 levels at those same times (P= 0.116, P=0.712, P=0.895, respectively), were similar between the two groups. Luteal perfusion was decreased (D10: P=0.025; D11: P=0.036; D12: P=0.0181; D13: P=0.0313) in the eCG group compared to control mares from the tenth to thirteenth day after ovulation. Greater glandular diameter (P= 0.0496) and epithelial height (P= 0.0373) of endometrium were observed in the eCG group at 10 days after ovulation, but not at 14 days after ovulation (P=0.7351 and P=0.8495, respectively). Expression of ESR1 (P=0.003) and P19 (P=0.001) genes were reduced in the eCG group. It was concluded that the eCG treatment reduced the luteal perfusion and repressed ESR1 and P19 expression in the uterus of transitional mares. Keywords: corpus luteum, equine, fertility, gene expression, uterus