PARENT SESSION
FUNCTION AND REGULATION OF THE CORPUS LUTEUM
Laurel
7:30 AM-10:00 AM

(464) RELATIVE CHANGES IN mRNA EXPRESSION FOR ANGIOPOIETIN AND RECEPTORS Tie IN BOVINE CORPUS LUTEUM DURING ESTROUS CYCLE AND PROSTAGLANDIN F₂-INDUCED LUTEOLYSIS .

Tanaka, Jun¹, Acosta, Tomas¹, Berisha, Bajram², Tetsuka, Masa¹, Kobayashi, Shu-ichi¹, Schams, Dieter², Miyamoto, Akio¹, ¹ Dept of Animal Science, Obihiro, Japan² Institute for Physiology, Freising-Weihenstephan

ABSTRACT- Local mechanisms of angiogenesis and angiolysis in the corpus luteum (CL) directly relate to the luteal function. Recently, several studies showed that angiopoietin (ANPT)-2 regulates remodeling of microvasculature and acts as a competitive inhibitor of ANPT-1 by binding to Tie2 without transducing an activating signal. However, little is known about ANPT and its tyrosine kinase receptor Tie in the bovine CL. Thus, this study aimed to investigate 1) the relative changes in the expression of mRNA for ANPT and Tie in the bovine CL during the estrous cycle and prostaglandin (PG) F₂-induced luteolysis, and 2) the effect of ANPT-2 on progesterone (P) release from microdialyzed CL at late stage of the estrous cycle. The CL were classified into 4 stages as described by Ireland et al (I: early, II: mid, III: late, IV: regressing). The expression of mRNA for ANPT-1, ANPT-2, Tie1 and Tie2 was detected by semi-quantitative RT-PCR in the bovine CL during the estrous cycle and PGF₂-induced luteolysis. The levels of ANPT-1 mRNA in early and regressing CL were lower than those in mid and late CL, whereas ANPT-2 mRNA expression did not change during the estrous cycle. Consequently, the ANPT-2/ANPT-1 ratio was high in early and regressing CL. The Tie1 mRNA expression did not change, while Tie2 mRNA expression decreased as the CL aged. In the regressing CL by PGF₂, ANPT-1 mRNA expression started to decrease from 4 h after PGF₂ injection. The ANPT-2 mRNA expression temporally increased at 2 h, but it returned to the basal level after 4 h. Thus, the ANPT-2/ANPT-1 ratio was increased by PGF₂ administration, and the high level was kept until 64 h after PGF₂ treatment, suggesting that ANPT-2 may be involved in blood vessel degeneration. The luteolytic administration of PGF₂ had no effect on the Tie1 and Tie2 mRNA expression. In the study with in vitro microdialysis system, an infusion of ANPT-2 (100 ng/ml) acutely inhibited P release from late CL. The present results suggest that ANPT-2 regulates P secretion as well as vascular degeneration in the CL during luteolysis. Supported by JSPS grants.

KEY WORDS: angiopoietin, angiolysis, corpus luteum, bovine