Evidence for a Local Endothelin-Angiotensin-Atrial Natriuretic Peptide Systemin Bovine Mature Follicles In Vitro: Effects on Steroid Hormones and Prostaglandin Secretion1

Abstract

Recent evidence suggests the presence of a functional endothelin-angiotensin-atrial natriuretic peptide system at the ovarian level. This study aimed to investigate 1) the local interrelationships among angiotensin II (Ang II), endothelin-1 (ET-1), and atrial natriuretic peptide (ANP); 2) the possible effect of each vasoactive peptide on the secretion of steroid hormones and prostaglandins (PGs) in isolated bovine mature follicles; and 3) the expression of mRNAs for Ang II, ET-1, and ANP receptors in the theca layer of follicles at different developmental stages. Each preovulatory follicle obtained before the LH surge (based on the concentrations of steroids and PGs) received implants of 4 capillary dialysis membranes into the theca layer. The follicles were then incubated in organ culture chambers and perfused with Ringer's solution for 12 h. Stimulation by infusion of the different substances into the microdialysis system was carried out between 4 and 8 h. The infusion of ET-1 (10(-7) M) stimulated the release of ANP and estradiol but inhibited the release of androstenedione and progesterone. The infusion of ANP (10(-7) M) stimulated the release of Ang II, progesterone, and androstenedione. Moreover, the infusion of Ang II (10(-5) M) inhibited the release of ANP but stimulated the release of ET-1, progesterone, and estradiol. All three peptides examined increased PGE(2) and PGF(2) release. In the reverse transcription-polymerase chain reaction analysis, expression of the mRNAs for ET type A and type B, and Ang II type 1 receptors did not change with the follicular size and the intrafollicular estradiol concentrations. Expression of the mRNA for the Ang II type 2 receptor dropped in follicles when the estradiol concentration ranged from 20 to 180 ng/ml and increased again when the estradiol concentration was > 180 ng/ml. The levels of expression of ANP type C receptor mRNA were slightly greater in follicles with estradiol concentrations > 20 ng/ml than in follicles with estradiol concentrations < 20 ng/ml. These results demonstrate a complex interaction among Ang II, ET-1, and ANP that may contribute to increasing the follicular production of PGs and modulate steroidogenesis in the bovine mature follicle, thus providing evidence for a local functional endothelin-angiotensin-ANP system.

Production and binding of endothelin-2 (EDN2) in the rat ovary: endothelin receptor subtype A (EDNRA)-mediated contraction

“…Therefore, it is highly likely that the increased endothelin measured by immunometric assay 12 h after hCG represents production of EDN2 by granulosa cells of the periovulatory ovary. The low level of total endothelin that was detected in ovaries collected 48 h after PMSG is also consistent with the production and function of EDN1 described during earlier stages of follicular development (Tedeschi et al 1992;Acosta et al 1999;Flores 2000).…”

Changes in fibroblast growth factor 2 and its receptors in bovine follicles before and after GnRH application and after ovulation

“…The concentrations of progesterone and E 2 were determined directly in the FF with an enzyme immunoassay (EIA) using the second antibody technique (Meyer et al 1990, Acosta et al 1999. The effective dose for 50% inhibition (ED 50 ) of the assay was 6 ng/ml for progesterone and 3.5 pg/ml for E 2 .…”

“…The EIA for PGF 2a (Acosta et al 1999) was evaluated in different dilutions directly in FF without extraction. The standard curve for PGF 2a ranged from 0.6 to 700 ng/ml, and the ED 50 of the assay was 300-400 pg/ml.…”

Evidence that the effect of angiotensin II on bovine oocyte nuclear maturation is mediated by prostaglandins E2 and F2α

“…The LH surge stimulates the ovarian renin-angiotensin system (RAS), including an increase in the renin, prorenin, and angiotensin II (AngII) concentration in bovine follicular fluid (Nielsen et al 1994, Acosta et al 2000. Moreover, the interactions among LH, AngII, endothelin-1, and atrial natriuretic peptide increased follicular production of prostaglandins (PGs) and modulated steroidogenesis in the bovine preovulatory follicle (Acosta et al 1999). AngII has also been associated with follicular growth (Ferreira et al 2008) and ovulation in cows (Acosta et al 2000, Ferreira et al 2007.…”