Received September 19, 2002; Revised November 12, 2002; Accepted Novem- ber 12, 2002. Author to whom all correspondence and reprint requests should be addressed: Dieter Schams, Institute of Physiology, Technical University of Munich, Weihenstephaner Berg 3, D-85350 Freising, Germany. E-mail: physio@wzw. tum.de The Expression of Angiotensin and Endothelin System Members in Bovine Corpus Luteum During Estrous Cycle and Pregnancy Bajram Berisha, 1 Dieter Schams, 1 and Akio Miyamoto 2 1 Institute of Physiology, Technical University of Munich, Weihenstephaner Berg 3, D-85350 Freising, Germany; and 2 Department of Animal Science, Obihiro University of Agriculture and Veterinary Medicine, Obihiro 080, Japan. Endocrine, vol. 19, no. 3, 305–312, December 2002 0969–711X/02/19:305–312/$20.00 © 2002 by Humana Press Inc. All rights of any nature whatsoever reserved. 305 The aim of this study was to determine the changing profiles of the mRNA expression of members of angio- tensin and endothelin system in bovine corpus luteum (CL) from different stages of the estrous cycle and preg- nancy. Corpora lutea were accordingly assigned to the following stages; d 1–2, 3–4, 5–7, 8–12, 13–18, >18 (after regression) of estrous cycle and of early and late pregnancy (<4 and >4 mo). The block RT-PCR analysis of CL showed a significantly higher angioten- sin converting enzyme (ACE) mRNA expression during mid and late luteal phases as well as after regression, but lower levels during pregnancy. Full quantitative real-time RT-PCR (LightCycler) confirmed this pattern of ACE mRNA expression. The angiotensin receptor type 1 (AT1R) mRNA expression was relatively stable throughout the periods examined. In contrast, AT2R mRNA temporarily decreased on d 8–12, followed by an increase to the highest levels during late luteal phase, and it remained at high levels during regression and pregnancy. Concentration of angiotensin II (Ang II) pep- tide in luteal tissue was highest after ovulation (d 1–2), decreased afterward, increased again during late luteal phase, and decreased to lower levels during regres- sion and pregnancy. The mRNA expression and peptide concentration of endothelin 1 (ET-1) was high after ovu- lation followed by a decrease during mid and late luteal phases and increased again to the highest level after regression. The endothelin receptor type B (ETR-B) mRNA expression increased during late luteal phase and further after regression. In contrast, ETR-A and endo- thelin converting enzyme 1 (ECE-1) mRNA expression were relatively constant during all stages examined. In conclusion, the regulatory changes of both angioten- sin and endothelin family members during early luteal phase and again during late luteal phase suggest a pos- sible modulatory role of these vasoactive peptide fami- lies for bovine CL formation and regression. Key Words: Angiotensin II; endothelin-1; expression; corpus luteum; cow. Introduction It is indicated that the local angiotensin and endothelin systems may have important roles in ovarian physiology (1–5). Angiotensin II (Ang II) and endothelin-1 (ET-1) may regulate reproductive phenomena such as oocyte matura- tion, ovulation, and corpus luteum (CL) function (6–12). Most Ang II is generated in two sequential steps: renin catalyzes the conversion of angiotensinogen to the decapep- tide Ang I, which is subsequently hydrolyzed by angioten- sin converting enzyme (ACE) to form Ang II (13). Two main types of Ang II receptor (AT1R and AT2R) located on the cell membrane have been characterized (14). The three types of endothelin family members (ET-1, ET-2, and ET-3) are derived from three different precursors, the pre-proendothelins, which are proteolytically processed by endopeptidases, to generate the inactive big ET. Big ET-1 is cleaved by endothelin converting enzyme-1 (ECE-1) to generate the 21-amino acid active vasopeptide. The ETs are produced in various tissues, but ET-1 is the only isoform synthesized and secreted by vascular endothelial cells. Two endothelin receptor subtypes (ETR-A and ETR-B) have been identified (15). Both Ang II and ET-1 stimulate vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (FGF2), the two most important angiogenic factors. Ang II induces VEGF expression in cardiac microvascular endo- thelial cells (16) and potentiates VEGF-mediated angiogenic activity through up-regulation of VEGFR-2 in retinal micro- vascular endothelial cells (17). Ang II and ET-1 regulate FGF2 production in endothelial cells (18). Moreover, it has been reported that both Ang II and ET-1 are most potent vasoconstrictors. There is now clear evidence that the vaso- active peptides Ang II and ET-1 may play an important role during physiological and induced luteolysis in cows. Ang II and ET-1 may be responsible for the observed decrease of blood flow in mid-cycle corpus luteum (CL) after induced luteal regression and suggest an important role to trigger the luteolytic cascade (19). Ang II and ET-1 may have also direct effects on luteal cells by inhibiting progesterone production