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EXPRESSION AND LOCALIZATION OF ANGIOTENSIN SYSTEM MEMBERS IN THE BOVINE OVARY.
Schams, Dieter1, Berisha, Bajram1, Amselgruber, Werner2, Miyamoto, Akio3, 1 2 3
ABSTRACT- There is now clear evidence that the ovarian renin-angiotensin system (RAS) regulates ovarian function by paracrine/autocrine actions of angiotensin II (Ang II).This study aimed to determine local changes of expression and localization of (RAS) members in the defined stages of follicular growth and the corpus luteum (CL) development during the estrous cycle and pregnancy. Follicles were classified into five classes (<0.5; 0.5-5; 5-20; 20-180: >180 ng/ml) according to the follicular fluid estradiol-17b (E) content. The corresponding size of follicles was 5-7, 8-10, 10-13, 12-14 and >14 mm, respectively. The CL were assigned to the following stages: Days 1-2, Days 3-4, Days 5-7, Days 8-12, Days 13-18, Days 18 and later, and of pregnancy. In follicles, angiotensin converting enzyme (ACE) mRNA by RT-PCR was expressed in theca interna (TI) with a peak in class 20-180 ng/ml (E), but granulosa cells (GC) were negative. Angiotensin type 1 receptor (AT1R) mRNA was constantly expressed in TI throughout all classes, while AT2R mRNA expression temporarily dropped in class 20-180 ng/ml (E). Both Rs were strongly expressed in GC. ACE protein was immunohistochemically localized in endothelial cells of TI in all classes with a tendency of stronger staining in smaller follicles, but GC was negative. In CL, the highest ACE mRNA expression was detected between mid luteal and regression phase. The AT1R mRNA expression increased to the higher levels from mid to regression phase, but remained low during pregnancy. In contrast, AT2R mRNA temporarily decreased during mid luteal phase. Concentrations of Ang II peptide in CL were highest after ovulation (Days 1-2) and dropped afterwards to the lower levels, followed by a significant increase during late luteal phase and again lower levels during regression and pregnancy. The ACE protein was predominantly localized in endothelial cells and was very distinct during the early and mid luteal phases, followed by a clear decline afterwards. In conclusion, the results give the evidence for local dynamics of RAS in the bovine ovary, and support the concept that the RAS is involved in the regulation of follicle development and luteal function. Supported by DFG and JSPS grants.
KEY WORDS: bovine, corpus luteum, follicular development, angiotensin system