RU486-Treated Rats Show Endocrine and Morphological Responses to Therapies Analogous to Responses of Women with Polycystic Ovary Syndrome Treated with Similar Therapies1

Abstract

Administration of 4 mg of the antiprogestagen RU486 to 4-day-cyclic rats over 8 consecutive days starting on the day of estrus (Day 1) induced and anovulatory cystic ovarian condition with endocrine and morphological features similar to those exhibited in polycystic ovarian disease (PCO). To determine whether the RU486-treated rat responds in an analogous fashion to therapies similar to those that have been used to treat human PCO, RU486-treated rats were injection on Days 5 and 7 with 1) 1 mg of an LHRH antagonist (LHRHa), 2) 5 IU of human FSH (hFSH), 3) 2 mg of the antiandrogen flutamide (FLU), 4) 1 mg of the antiestrogen tamoxifen (TMX), or 5) 1 mg of the dopamine agonist bromocriptine (BRC). Controls were intact cyclic rats decapitated on estrus and rats injected with RU486 and the corresponding vehicles (saline or 70% ethanol) used with LHRHa, hFSH, FLU, TMX, and BRC injections. RU486-treated rats were decapitated on Day 9, and the serum concentrations of LH, FSH, prolactin (PRL), testosterone (T), and estradiol-17 beta (E2) were determined. Pituitary and ovary weight, number of follicular cysts, size of the corpora lutea, and rates of follicular growth and atresia were also noted. Finally, the ovulatory response to ovine LH (oLH) in rats treated with RU486 and injected with various doses of hFSH (5, 10, or 20 IU) was evaluated. While administration of LHRHa and of TMX decreased the serum concentrations of LH, T and E2 and the LH/FSH and T/E2, ratios, and injections of BRC and of FLU increased the serum concentration of LH and T, the administration of hFSH (10 IU) to RU486-treated rats increased only the serum levels of E2. All treatments decreased, though in different degrees, both the number of cysts and the rate of follicular atresia, and stimulated follicular growth. The positive effects on follicular growth and atresia were significantly higher in those rats injected with hFSH. Moreover, RU486-treated rats injected with different doses of hFSH ovulated in a dose-dependent manner in response to oLH. Rates deprived of the actions of progesterone through the administration of the antiprogestagen RU486 had 1) endocrine and morphologic alterations comparable to those observed in women with PCO, 2) analogous responses to therapies similar to those that have been used to treat human PCO, and 3) an ovulatory response to combined treatment with FSH and LH. These results establish the fundamental adequacy of using the RU486-treated rat as a PCO model.

Permselectivity of blood follicle barriers in mouse ovaries of the mifepristone-induced polycystic ovary model revealed by in vivo cryotechnique

“…Following 2-4 days of injection of mifepristone, the normal estrous cycles were disturbed to be 'persistent vaginal cornification' or consecutive estrous stage until the time of tissue fixation (Ruiz et al 1996). The persistent vaginal smear was consistent with the findings of previous report using the oral administration of mifepristone (Gao & Short 1994).…”

“…However, the administration of mifepristone to rats was recently used as a good model of human PCO syndrome (Singh 2005, Lakhani et al 2006. The mifepristone-induced PCO syndrome model in rats is appropriate in some aspects to simulate the PCO syndrome condition of ovaries in humans, because not only ovarian histology but also the hormone levels were quite similar to those of humans (Sanchez-Criado et al 1992, 1993, Ruiz et al 1996. Although these studies showed that the mifepristone-induced PCO syndrome model was reversible during the experimental course (Singh 2005), the PCO syndrome model is useful for histopathological studies on the mechanism of chronic anovulation and vascular functions in greater detail, considering the recent technical development of transgenic animals.…”

“…One of the PCO models, which is induced by mifepristone and considered in rats to be a PCO syndrome model 'fundamentally adequate' to investigate the effect of PCO syndrome-like endocrinological perturbations on ovarian physiology and histology during the short term of 1-2 weeks, was used (Ruiz et al 1996, Lakhani et al 2006. The IVCT is a kind of cryofixation method, in which the target organs of living animals are directly frozen in vivo without tissue resection or perfusion fixation, and enables the capture of transient changes in tissue and cell morphology without the artifacts inevitable by the conventional tissue preparation methods.…”

Attenuin: What It Is, How It Works and What It Does

“…These discrepancies may be due to the different origins of FF (human vs. bovine), to the experimental model used (static vs. dynamic incubation) and to the absence or presence of inhibin. Previous results published by this research group (Tébar et al, 1996(Tébar et al, , 1998 support the hypothesis that the pituitary loses sensitivity to attenuin when follicles reach the preovulatory size, which would account for estradiol suddenly exerting a positive feedback. This intriguing mechanism, by which pituitaries become insensitive to attenuin and/or sensitive to the stimulatory action of GnRH, may provide an extra clue for understanding estrous cycle length regulation.…”

“…This factor would limit the physiological timing (proestrous afternoon) as well as the magnitude (preovulatory secretion) of pituitary responsiveness to GnRH. This research thus shows how a decrease in endogenous FSH levels during diestrus, with a consequent reduction in attenuin production but no significant effect on estradiol levels, gives rise to a 1-or 2-day advancement of blunted preovulatory LH surges in 4- (Tébar et al, 1996, 1998) and 5-day (Sánchez-Criado et al, 1996 cyclic rats, respectively. This suggests that, in physiological circumstances, submaximal FSHdependent ovarian attenuin bioactivity prevents the premature LH surge in diestrus by antagonizing the secretory effect of GnRH (Koppenaal et al, 1991;Tébar et al, 1998) and/or the sensitizing effect of estradiol on the pituitary (Schuiling et al, 1999).…”