7:30 AM-10:00 AM
(95) ANGIOPOIETIN AND Tie mRNA EXPRESSION IN DEVELOPING, MATURE AND ATRETIC FOLLICLES IN THE BOVINE OVARY.
Hayashi, Ken-Go1, Acosta, Tomas1,3, Tetsuka, Masa1, Hayashi, Misato1, Berisha, Bajram2, Schams, Dieter2, Miyamoto, Akio1, 1 Dept of Animal Science, Obihiro, Japan3 Departamento de Fisiologia, San Lorenzo, Paraguay2 Institute for Phisiology, Freising-Weihenstephan, Germany
ABSTRACT- Angiogenesis in the theca layer is involved in the local mechanisms of follicular growth and ovulation. Recently, angiopoietin (ANPT) system has been shown to regulate the blood vessel formation, stabilization, and degeneration. This study therefore aimed to investigate 1) the mRNA expression for ANPT and its receptor Tie in the bovine developing, mature, and atretic follicles, and 2) the effect of ANPT-2 on the secretion of steroid hormones from mature follicles in vitro. Developing follicles were classified into 5 groups according to the follicular fluid (FF) content of estradiol (E) (<0.5 ng/ml, 0.5-5 ng/ml, 5-20 ng/ml, 20-180 ng/ml, and >180 ng/ml) with progesterone (P) concentrations <100 ng/ml. In the developing follicles with E concentration <180 ng/ml, a semi-quantitative RT-PCR revealed that the levels of ANPT-2 mRNA and ANPT-2/ANPT-1 mRNA ratio in theca cells (TC) were higher than those in mature follicles with the highest E content (>180 ng/ml). The Tie-1 and Tie-2 mRNA expressions in TC of small follicles (<0.5 ng/ml) were lower than those of larger follicles. Mature and atretic follicles were collected from ovaries with a regressing corpus luteum (follicular phase). Based on the characteristics of granulosa cells (GC) and concentrations of E and P in FF, they were separated into 3 groups; E dominant, early atretic, and atretic follicles. TC of early atretic follicles showed higher ANPT-2/ANPT-1 mRNA ratio than that of mature or atretic follicles. In GC, ANPT-1 mRNA was expressed at similar level as that in TC, whereas ANPT-2 mRNA was only weakly expressed. TC expressed Tie-2 mRNA at higher levels in mature and early atretic follicles than atretic follicles, whereas they expressed Tie-1 mRNA at higher levels in early atretic and atretic follicles than that in mature follicles. In the in vitro microdialysis system, ANPT-2 (100 ng/ml) stimulated E and P secretion, but not androstenedione. The present results strongly suggest that ANPT and Tie are involved in the vascular and secretory changes during follicular development and atresia in the bovine ovary. Supported by JSPS grants.
KEY WORDS: angiogenesis, angiopoietin, follicle, bovine