Effects of Ovarian Bisection on Response to Intrafollicular Injection of PGF2α and on Follicular Development in Ewes

Abstract

Transfer of prostaglandin F₂α (PGS₂α) from an injected follicle to a corpus luteum (CL) in the same ovary was examined. All ewes were unilaterally-ovariectomized and the remaining ovary was either bisected and reconstructed with a latex septum or marked with India ink in the plane of bisection (sham-operated) on day-3 postestrus. An intrafollicular injection (20 µ1) was made on day 9 according to the following randomized treatments: Bisected ovary plus PGF₂α (250 ;µg) in the half of the ovary containing the CL (adjacent; four ewes) or opposite to the CL (three ewes); bisected ovary plus Tham buffer (four ewes); sham-operated plus PGF₂α (six ewes) or Tham buffer (six ewes). Length of estrous cycles (days) for ewes in which the ovary was bisected plus PGF₂α adjacent to the CL (12.1 ± 4), bisected plus PGF₂α opposite to the CL (11.5 ± .8) and sham-operated plus PGF₂α (11.9 ± 3) did not differ. However, they were shorter (P<.01) than cycles of ewes with bisected ovaries plus buffer (17.5 ± .5) or sham-operated plus buffer (16.8 ± .3). Prior to injection on day-9 postestrus, ewes with bisected ovaries had lower (P<.05) jugular venous progesterone (1.3 ± .3 ng/ml) and higher luteinizing hormone (LH; 3.3 ± 1.7 ng/ml) than ewes with sham-operated ovaries (2.7 ± .3 and .4 ± .1, respectively). Concentrations of estradiol-17ß (pg/ml) on day 9 were not different in ewes with bisected (3.4 ± .8) or sham-operated (2.7 ± .3) ovaries. The profiles of progesterone decline over time were similar in all ewes injected with PGF₂α regardless of surgical treatment or site of injection but were not parallel to those observed in buffer-treated ewes. Concentrations of estradiol-17ß increased only when concentrations of progesterone declined to low levels following injection of PGF₂α. It is suggested that PGF₂α injected into a follicle in an ovary bearing a corpus luteum is luteolytic through a local extra-ovarian pathway. Follicles (≥2mm) were recorded at each laparotomy by location relative to the corpus luteum as a preliminary examination of a possible local relationship between corpora lutea and follicular development in ewes. Bisected ovaries had fewer (P<.01) total follicles and fewer follicles 2 to 5 mm than sham-operated ovaries on days 3 and 9. On day 9 there were more follicles ≥5 mm and greater follicular volume in the half of the ovary containing the corpus luteum (P<.05) in bisected or sham-operated ovaries. However, a greater mean follicular diameter adjacent to the CL (P<.05) was evident only in bisected ovaries on day 9. It is suggested that corpora lutea may influence follicular growth locally within the ovary. Copyright © 1977. American Society of Animal Science . Copyright 1977 by American Society of Animal Science.