Follicular cysts occur after a normal estradiol-induced GnRH/LH surge if the corpus hemorrhagicum is removed

Abstract

The pathophysiology underlying follicular cysts appears to be lack of an estradiol (E 2 )-induced GnRH/LH surge due to hypothalamic insensitivity to E 2 . In addition, progesterone (P 4 ) can cause animals with follicular cysts to resume normal cyclicity and normal hypothalamic responsiveness to E 2 . We postulated that follicular cysts may be a pathological manifestation of a physiological state that cows, and possibly other species, go through during the normal estrous cycle but the rise in P 4 following ovulation induces them back to normal hypothalamic responsiveness to E 2 . Based on this hypothesis, we expected that removal of the ovary containing the corpus hemorrhagicum would prevent the normal rise in P 4 following ovulation and induce development of follicular cysts. Cows (n 5 24) on day 7 of the estrous cycle were treated with prostaglandin F 2a (PGF 2a ) and time of ovulation was detected by ovarian ultrasonography every 8 h. Immediately following detection of ovulation, cows were randomly but unequally assigned to have the ovary containing the corpus hemorrhagicum removed (TRT; n 5 16) or the ovary opposite to the corpus hemorrhagicum removed (CON; n 5 8). Cows were subsequently evaluated by daily ultrasound and blood sampling to determine follicular dynamics. Ovulation was detected at 93.7 6 4.5 h after PGF 2a injection. All CON cows had a normal estrous cycle length (22.0 6 0.6 days) after ovariectomy (OVX). Half of the TRT cows became anovular (TRT-ANO; n 5 8) after OVX with large anovular follicles developing on the ovary (maximal size, 25.4 6 1.4 mm; range, 20-32 mm). However, eight TRT cows ovulated (TRT-OV; n 5 8) 7.3 6 0.6 days after OVX. Control cows had a normal P 4 rise after ovulation. Removal of the newly formed corpus hemorrhagicum prevented the rise in circulating serum P 4 in TRT-ANO cows throughout the 25-day experimental period. The TRT-OV cows had a delayed increase in circulating P 4 but it was normal in relation to time of ovulation. Serum E 2 concentrations were similar among groups (TRT-OV, TRT-ANO and CON cows) until 7 days after OVX. Serum E 2 concentrations then decreased in TRT-OV and CON cows but remained elevated (> 5 pg/ml) in TRT-ANO cows. Thus, the endogenous increase in circulating E 2 that induces the GnRH/LH surge and estrus is sufficient to induce cows into a physiological state that resembles follicular cysts if it is not followed by increased circulating P 4 . Reproduction (2005) 129 737-745Introduction Follicular cysts have been reported in many mammalian species, including cattle (Roberts 1971, Kesler & Garverick 1982, swine (Heinonen et al. 1998), dogs (Arbeiter 1993, rabbits (Lopez-Bejar et al. 1998), rats (Brawer et al. 1986), mares (McCue & Squires 2002), sheep (Christman et al. 2000), elephants (Brown et al. 1999) and women (Stein & Leventhal 1935). In cattle, this condition is characterized by large (generally $25 mm in diameter) anovular structures that persist on the ovary for at least 10 days in the absence of a corpus luteum (CL) (Roberts 1...

The absence of corpus luteum formation alters the endocrine profile and affects follicular development during the first follicular wave in cattle

“…Thus, our results suggest that both dominant follicles were healthy and had an ovulatory capacity in most of the CL-absent cattle. Our present results are consistent with a recent study in which the high incidence of co-dominant follicles was observed in the contralateral remaining ovary when the corpus haemorrhagicum was removed soon after ovulation (Gumen & Wiltbank 2005).…”

The Role of Luteinizing Hormone in Regulating Gene Expression During Selection of a Dominant Follicle in Cattle

“…The specific times were chosen because a diameter of 7.8-8.0 mm represents a time approximately 8-12 h before follicular deviation; therefore, it was expected that the 12-h time point would be close to the expected time of deviation and the 24-h time point approximately 12-16 h after deviation. Ovariectomy was performed using the colpotomy technique [26] at 12 and 24 h after acyline (or saline) treatment using an ecraseur (Jorgensen Laboratories, Inc.).…”

Molecular aspects of bovine cystic ovarian disease pathogenesis

“…In relation to endocrine signaling pathways, some of these studies have demonstrated altered expression of steroid and gonadotropin receptors , Marelli et al 2014. Other studies have postulated and tested the intrafollicular roles of steroids in regulating follicular development (Berisha et al 2002, Gümen & Wiltbank 2005.…”