Steroid hormones in bovine oviductal fluid during the estrous cycle
Résumé
Ovarian steroid hormones are major regulators of the physiology of the oviduct and reproductive events occurring within the oviduct. In order to establish a whole steroid profiling of the bovine oviductal fluid (OF) during the estrous cycle, contra- and ipsilateral (to the corpus luteum or pre-ovulatory follicle) oviducts were classified into four stages of the estrous cycle (n=18-25 cows/stage): post-ovulatory (Post-ov), mid luteal (Mid-lut), late luteal (Late-lut) and pre-ovulatory (Pre-ov) based on ovarian morphology and intra-follicular steroid concentrations. Steroids were extracted from pools of 150-200 μl OF (4-10 cows/pool; 3-4 pools per 'stage × side' group), purified, fractioned by high performance liquid chromatography and analyzed by gas chromatography coupled with tandem mass spectrometry. The concentrations of progesterone (P4) in ipsi-lateral OF increased from Post-ov (56.9 ± 13.4 ng/ml) to Mid-lut (120.3 ± 34.3 ng/ml) then decreased from Late-lut (76.7 ± 1.8 ng/ml) to Pre-ov (6.3 ± 1.7 ng/ml) and were 4 to 16 times higher than in contralateral OF. Most P4 metabolites followed similar patterns of variation. Concentrations of 17beta-estradiol (E2) were significantly higher at Pre-ov (290.5 ± 63.2 pg/ml) compared with all other stages (<118.3 pg/ml), with no difference regarding the side of ovulation. Concentrations of androstenedione displayed a pattern similar to that of E2 whereas other androgens, estrone and corticoids did not vary between stages or sides. In conclusion, a highly concentrated and fluctuating hormonal environment was evidenced in the bovine OF. These results could be useful to improve media for in vitro fertilization, embryo development and culture of oviductal cells.