The role of angiotensin II in the early stages of bovine ovulation.
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.
Ferreira
Rogério
R
Laboratory of Biotechnology and Animal Reproduction, BioRep, Federal University of Santa Maria, 97105-900 Santa Maria, Rio Grande do Sul, Brazil.
Oliveira
João Francisco
JF
Fernandes
Rafael
R
Moraes
José Ferrugem
JF
Gonçalves
Paulo Bayard
PB
D000804:Angiotensin II / Q000502:physiology*; D047228:Angiotensin II Type 1 Receptor Blockers / Q000494:pharmacology; D057912:Angiotensin II Type 2 Receptor Blockers; D057911:Angiotensin Receptor Antagonists; D000818:Animals; D002417:Cattle / Q000378:metabolism*; D005260:Female; D007987:Gonadotropin-Releasing Hormone / Q000494:pharmacology; D007093:Imidazoles / Q000494:pharmacology; D007267:Injections / Q000379:methods; D019808:Losartan / Q000494:pharmacology; D007986:Luteinizing Hormone / Q000494:pharmacology; D006080:Ovarian Follicle / Q000000981:diagnostic imaging / Q000187:drug effects / Q000502:physiology; D010060:Ovulation / Q000187:drug effects / Q000502:physiology*; D011725:Pyridines / Q000494:pharmacology; D011897:Random Allocation; D044139:Receptor, Angiotensin, Type 2 / Q000378:metabolism; D012084:Renin-Angiotensin System / Q000187:drug effects / Q000502:physiology*; D012504:Saralasin / Q000494:pharmacology; D014463:Ultrasonography
D047228:Angiotensin II Type 1 Receptor Blockers; D057912:Angiotensin II Type 2 Receptor Blockers; D057911:Angiotensin Receptor Antagonists; D007093:Imidazoles; D011725:Pyridines; D044139:Receptor, Angiotensin, Type 2; D000804:Angiotensin II; C073402:PD 123319; D007987:Gonadotropin-Releasing Hormone; D007986:Luteinizing Hormone; D012504:Saralasin; D019808:Losartan