Response: Angiotensin II: Does It Have a Direct Obligate Role in Ovulation?
Department of Obstetrics and Gynecology, Yale University, New Haven, CT 06510-8063. Science
(Impact Factor: 33.61).
09/1989; 245(4920):870-1. DOI: 10.1126/science.245.4920.871
Available from: Paulo Bayard Dias Gonçalves
- "Ovulation is inhibited by the administration of saralasin to in vitro perfused rabbit ovaries (Yoshimura et al. 1993). However, in rat, Ang II receptors were not detected in every developing follicle (Husain et al. 1987) and in preovulatory follicles with LH receptors (Daud et al. 1989), suggesting a species-specific effect of Ang II on ovulation. Cattle provide an excellent model for studying the ovulatory process, since the follicular environment can be easily modified by ultrasound-guided intrafollicular injection (Kot et al. 1995, Ginther et al. 2004) and accurately monitored on a day-to-day basis by ultrasonography in vivo (Savio et al. 1988, Ginther et al. 1989, Evans & Fortune 1997). "
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ABSTRACT: There is evidence that the renin-angiotensin system plays an important role in ovulation in cattle. Using an in vivo model, we investigated the role of angiotensin (Ang) II in bovine ovulation by injecting Ang II receptor antagonists into ovulatory follicles. Animals (n = 102) were pre-synchronized and, when the follicles reached 12 mm, they were given the respective treatment and the cows received GnRH agonist (i.m.) to induce ovulation. The ovulation rate was significantly lower when 100 mu M saralasin (Ang II receptor antagonist) was intrafollicularly injected (14.3%) in comparison with saline solution (83.3%). Based on these results, a second experiment was carried out to determine the timing of Ang II's critical role in ovulation. Saralasin inhibited ovulation only when applied at 0 and 6 h (16.7 and 42.9% ovulation rate in the 0- and 6-h groups respectively), but not at 12 h (100%) following GnRH agonist treatment. To investigate the subtypes of Ang II receptors implicated in the LH-induced ovulation, losartan (LO; AT(1)-Ang II receptor antagonist), PD123 319 (AT(2)-Ang II receptor antagonist), LO+PD123 319, or saline were intrafollicularly injected when the cows were challenged with GnRH agonist. Ovulation was inhibited by PD123 319 and LO+PD123 319 (50.0 and 33.3% on ovulation rate respectively), but not by LO or saline solution (100% ovulation in both groups). From these results, we suggest that Ang II plays a pivotal role in the early mechanism of bovine ovulation via the AT(2) receptor subtype.
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ABSTRACT: Angiotensin II was reported to play a key role in ovulation in rats and it seems also to be involved in the regulation of LH release. Thus, we studied the effect of chronic ACE inhibition on the menstrual cycle, measuring daily plasma estradiol, progesterone, LH and FSH, and renin and prorenin before and during the third month of treatment with enalapril (10 mg b.i.d.) in 10 mild essential hypertensive women. Blood pressure was normalized by treatment. The cyclical changes of steroids and gonadotrophins were unaffected in their temporal relationships and in the magnitude of their variation during the experimental cycle compared with the basal cycle. A synchronization of plasma prorenin with the other hormones was seen both before, as previously reported, and during enalapril treatment. Our data show that peripheral blockade of angiotensin I conversion does not affect the pituitary guidance of the ovarian hormonal response or the ovarian prorenin release during the menstrual cycle. Our data are in agreement with the hypothesis that circulating angiotensin II does not play a key role in the human fertility process and that hydrophilic ACE inhibitors can be safely used in the treatment of hypertensive women of reproductive age.
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