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In 14 cyclic ewes, the oestrus-associated glycoprotein in the oviducal fluid was never detected between Days 7 and -2 of the oestrous cycle and it was present in 5% of fluid samples collected on Day -1, 59% on Day 0, 96% on Day 1, 100% on Day 2, 79% on Day 3, 31% on Day 4, 16% on Day 5, and 4% on Day 6. Its presence generally coincided with the period of high flow rate of oviducal fluid which occurs around oestrus. The duration of detectable levels of the oestrus-associated glycoprotein did not vary significantly during the breeding season from a mean (+/- s.d.) of 3.9 +/- 1.0 days. However, the peak flow rate of oviducal fluid dropped from 1.63 +/- 0.50 (early) to 1.38 +/- 0.40 (mid-) and to 0.85 +/- 0.21 ml/day late in the season. Anoestrous ewes (3) induced to ovulate by treatment with progesterone implants and gonadotrophin showed low peak fluid flow rates (0.92 +/- 0.30 ml/day) and the presence of the oestrus-associated glycoprotein for a shorter period (2.7 +/- 0.7 days). Pregnancy (N = 3) did not appear to prolong the production of the protein. The injection of 25 micrograms oestradiol benzoate into 3 anoestrous, 2 mid-cycle and 9 ovariectomized ewes caused an increase in fluid flow rate and appearance of the glycoprotein 1-2 days later. The glycoprotein was present for a longer period in response to the exogenous oestrogen--6.8 +/- 1.6 days in the ovariectomized ewes, 7.9 +/- 1.3 days in anoestrous ewes, and 8.4 +/- 0.8 days in the dioestrous ewes.(ABSTRACT TRUNCATED AT 250 WORDS)

Samples of oviducal fluid were collected daily from sheep with indwelling catheters. Fluid samples taken from both oviducts of 2 sheep for 2 cycles during the middle of the breeding season (April/May) (8 sets of data) were compared with 9 sets of data generated from 2 cycles in 3 sheep later in the breeding season (June/July). Around the period of oestrus, the output of oviducal fluid increased to a peak volume of 1.56 +/- 0.35 ml per day (mean +/- s.d.) compared with a mid-cycle volume of 0.49 +/- 0.29 ml. Later in the breeding season, the flow rates were lower, but showed the same trend (0.91 +/- 0.24 ml at the peak and 0.25 +/- 0.18 ml 7 days later). The total amount of protein secreted by the oviduct each day increased 2-4-fold around the time of oestrus, with higher levels in mid-season ewes. When oviducal fluids were fractionated by SDS electrophoresis, a novel glycoprotein, subunit size of Mr 80-90 000 was identified in samples for 3-6 days of each cycle, coinciding with the period of high fluid flow rate. This protein first appeared in the oviducal fluid on the day of oestrus or the following day and it represented 1 of the 2 major glycoproteins in oviducal fluid as assessed by periodic acid-Schiff (PAS) staining. A PAS-positive protein (Mr 80-90 000) was also detected in fluid taken after oestrus on native highly cross-linked gradient gels after electrophoresis at pH 3.1 but not at pH 8.3. Both gradient gel systems showed an increase in high molecular weight material (Mr greater than 10(6] in fluid taken soon after oestrus.