Effects of follicular fluid on the transport of porcine oocytes into the oviduct at ovulation

Three experiments were conducted to determine whether follicular fluid (FF) enters the oviduct and plays any role in the transport of oocytes into the oviduct. Experiment 1: Oestrus and ovulation were synchronized in cycling gilts (n = 21) over a 15 day period of feeding Regumate(R) and injections o f 1000 IU pregnant mare's serum gonadotrophin (PMSG) 24h after the last Reg umate(R) feed and 500 IU human chorionic gonadotrophin (hCG) 80 h after PMS G. Ipsi-lateral aspiration of FF and salpingectomy (group 1, n = 7), aspira tion of FF without salpingectomy (group 2, n = 7) or ligation of the oviduc t between the ampulla and infundibulum (group 3, n = 7) was performed endos copically prior to ovulation (34-36h after hCG). Ipsi-lateral (group 2 and 3) and contra-lateral salpingectomy was carried out in all gilts post ovula tion, 42-44 h after hCG. The oviducts were flushed with 1 mi saline and the samples as well as the aspirated FF were analysed for progesterone and est radiol by RIA methods. In group 1 both progesterone and estradiol concentra tions did not differ before and after ovulation. Withdrawal of FF from the ipsi-lateral ovary by aspiration (group 2) or ligation of the oviduct (grou p 3) did not influence the steroid content within the oviducts. Similarly l ow progesterone concentrations were measured in ipsi- and contra-lateral ov iducts after ovulation (group 2: 0.29 +/- 0.17 versus 0.24 +/- 0.35ng/ml an d group 3: 0.22 +/- 0.19 versus 0.21 +/- 0.22nglml). The high content of pr ogesterone of FF (269.7 +/- 67.9 and 389.6 +/- 226.5 ng/ml in group 1 and 2 , respectively) was not reflected in the oviductal fluid. Experiment 2: In five gilts 0.06 ml H-3-progesterone (30 000 dpm) were applied via a fine 27 G injection needle into the largest three follicles of the ipsi-lateral ov ary prior to ovulation (34-36 h after hCG). The oviducts were flushed follo wing ovario-salpingectomy 42-44 h after hCG. All follicles had ovulated. Th e oviductal flushings and oviductal and ovarian tissue were analysed for la belled progesterone. No differences were measured in the content of 3H-prog esterone of oviductal flushings and of both oviductal and ovarian tissues b etween the ipsi-lateral injection and contralateral control sides. The main part of the counts detected was within the range of background dpm values. Only 2.4% of the initial counts were recovered from fluid and tissue sampl es. Experiment 3. In a subsequent study FF was cautiously aspirated by endo scopy from follicles of the ipsi-lateral ovary 34-36h after hCG (n = 12 gil ts). Postovulatory (58 h after hCG), both oviducts were flushed and the ooc ytes were recovered. To test the influence of follicle puncture alone on th e process of ovulation (n = 8 gilts), the aspiration needle alone was prick ed into the follicles of the ipsi-lateral ovary, without any fluid aspirati on. Despite the cautious aspiration of FF from 89 follicles, 26 oocytes wer e recovered together with the FF. Eighty-six postovulatory follicles were o bserved on the ipsilateral ovary. Out of 57 oocytes able to reach the ovidu ct, 29 oocytes were flushed from the oviduct (50.4 +/- 28.1%). From the con tra-lateral control oviduct 71 oocytes out of 91 ovulations (69.0 +/- 33.9% ) were recaptured. Puncture of follicles without aspiration did not influen ce ovulation compared with the control (recovery rate 68.2 and 79.6%, respe ctively). Results indicate (1) on the basis of the low progesterone level w ithin the oviductal fluid that only a small amount of FF seems to reach the oviduct at ovulation, and (2) FF does not appear to be a compulsory carrie r of the porcine oocyte at ovulation.