The mRNA expression of angiotensin and endothelin system members in bovine ovarian follicles during final follicular growth

Recent observations suggest that vasoactive peptides angiotensin II (Ang II) and endothelin-1 (ET-1) regulate ovarian functions. The aim of this study was to investigate mRNA expression by semi-quantitative RT-PCR for the members of the angiotensin system such as angiotensin converting enzyme (ACE), angiotensin type 1 and 2 receptors (AT1R and AT2R), and also for the members of the endothelin system such as ET-1, endothelin converting enzyme-1 (ECE-1), endothelin A and B receptors (ETR-A and ETR-B) in theca interna (TI) and granulosa cell (GC) compartments of bovine follicles during final follicular growth. A classification of follicles into five groups (<0.5; >0.5-5; >5-20; >20-180; >180 ng/ml) was performed according to the estradiol-17β (E) content of follicular fluid. For the angiotensin system, the mRNA expression of ACE in TI significantly increased with E content in preovulatory follicles. In contrast, the GC of follicles did not express ACE mRNA. The mRNA expression of AT1R and AT2R in TI and GC was consistently detected throughout the different follicular stages. For the endothelin system, mRNA expression of ECE-1 in TI and GC increased during final growth of follicles. The mRNA expression of ET-1 in TI decreased in large follicles, whereas in GC it was completely negative at all stages of the follicle. In TI, mRNA expression of both ETR-A and B was constant, while in GC the expression of ETR-A mRNA increased with follicular E content. In conclusion, it is clear from our results that distinct regulatory changes of mRNA expression for some members of the angiotensin and endothelin systems occur in mature follicles. Particularly, a significant increase in the mRNA expression of both ACE and ECE toward the final maturation of follicles suggests the possible modulatory roles of Ang II and ET-1 in supplying the optimal microenvironment of ovulatory follicles.