Oestrogen and seasonal effects on the production of an oestrus-associated glycoprotein in oviducal fluid of sheep.

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)