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This Article Full Text Full Text (PDF) All Versions of this Article: 69/6/2078    most recent biolreprod.103.017152v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Hayashi, K.-G. Articles by Miyamoto, A. Search for Related Content PubMed PubMed Citation Articles by Hayashi, K.-G. Articles by Miyamoto, A. Agricola Articles by Hayashi, K.-G. Articles by Miyamoto, A.

Involvement of Angiopoietin-Tie System in Bovine Follicular Development and Atresia: Messenger RNA Expression in Theca Interna and Effect on Steroid Secretion¹

Department of Agricultural and Life Science⁴ Field Center of Animal Science and Agriculture,⁵ Obihiro University of Agriculture and Veterinary Medicine, Obihiro 080-8555, Japan Departamento de Fisiologia,⁶ Facultad de Ciencias Veterinarias Universidad Nacional de Asuncion, 1061 San Lorenzo, Paraguay Institute of Physiology,⁷ Technical University of Munich, 85350 Freising-Weihenstphan, Germany

Angiogenesis is involved in the local mechanisms that regulate follicular development and ovulation. Recently, the angiopoietin (ANPT)-Tie system has been shown to be required to regulate angiogenesis and blood vessel regression. Expression of the ANPT-Tie system in the cyclic ovary suggests that the relative changes in the expression of ANPT-1 and ANPT-2 influence the stability of ovarian blood vessels. In this study, we investigated 1) the mRNA expression for ANPT-1, ANPT-2, and endothelial cell-specific receptors Tie1 and Tie2 in the theca interna (TI) of the bovine developing, mature, and atretic follicles by using a semiquantitative reverse transcription polymerase chain reaction assay and 2) the effect of ANPT on the secretion of steroid hormones from bovine preovulatory follicles in vitro using a microdialysis system (MDS) implanted in the thecal layer. Bovine follicles were classified as developing, mature, and atretic according to size, follicular fluid content of estradiol (E₂) and progesterone (P₄), and characteristics of granulosa cells (GCs). Both ANPT and Tie mRNA were expressed in the TI, whereas GCs expressed ANPT mRNA only. The expression of ANPT-2 mRNA was decreased in the mature follicles. This decrease resulted in a decrease in the ANPT-2:ANPT-1 ratio (an index of instability of blood vessels), indicating that the blood vessels became more stable or mature. The early atretic follicles showed a higher ANPT-2:ANPT-1 ratio and higher Tie2 mRNA expression than did other follicles at healthy or later atretic stages. This finding may imply that blood vessels become unstable at the initial stage of follicular atresia. In both mid and late atretic follicles, Tie2 mRNA expression dramatically decreased, indicating a disruption of the ANPT-Tie system. In the MDS experiment, an infusion of ANPT-1 or ANPT-2 increased P₄ release, whereas both ANPTs inhibited the release of androstenedione. ANPT-1 also increased E₂ release. These results showed that the mRNA expression for ANPT-1, ANPT-2, Tie1, and Tie2 changes during follicular development, maturation, and atresia in bovine follicles and that ANPTs affect steroidogenesis in the preovulatory follicle. The results suggest that the ANPT-Tie system is involved the structural (angiogenesis) and secretory changes that occur during follicular development and atresia.

¹ This study was supported by the Grant-in-Aid for Scientific Research of the Japan Society for the Promotion of Science (JSPS), the 21st Century COE Program (A-1) of Ministry of Education, Culture, Sports, Science, and Technology, Japan, and the Inoue Foundation for Science (IFS). T.J.A. and M.M. were postdoctoral fellows supported by JSPS and IFS, and the COE program, respectively.

² Correspondence. FAX: 81 155 49 5593; akiomiya{at}obihiro.ac.jp

³ Current address: Department of Animal Health and Biomedical Sciences, University of Wisconsin, Madison, WI 53706

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