Abstract. Angiotensin II (Ang II), a vasoactive peptide, is secreted by the bovine oviduct and is involved in modulation of local oviductal contraction. Ang II biosynthesis and release during the normal estrous cycle and the effects of luteinizing hormone (LH) and ovarian steroids on biosynthesis and secretion of Ang II were investigated. During the preovulatory period, increases in mRNA expression for Angiotensin converting enzyme 1 (ACE-1) and release of Ang II peptide were detected. Microdialysis of oviductal segments in vitro showed that LH alone significantly increased Ang II release, and combined infusion of LH+E2+P4 caused an increase in Ang II release. In cultured oviductal epithelial cells, LH increased Ang II release and ACE-1 mRNA expression, and E2+P4 enhanced stimulatory effect of LH on Ang II release and ACE-1 mRNA expression. Thus, it can be concluded that the oviductal Ang II system is upregulated by LH and ovarian steroids during the periovulatory period and may enhance local oviductal contraction. These events could stimulate transport of gametes to the fertilization site. Key words: Angiotensin II (Ang II), Angiotensin converting enzyme 1 (ACE-1), Fallopian tube, Luteinizing hormone (LH), Ovarian steroids, Uterine tube (J. Reprod. Dev. 55: [570][571][572][573][574][575] 2009) he oviduct controls simultaneous opposite movements of gametes to the fertilization site and passage of the embryo into the uterus at a precise developmental stage. Estrous cycle-dependent oviductal contractile patterns appear to be attributed to these timely movements of gametes and embryos. Studies of spontaneous oviductal contractile patterns in the cow have revealed that the amplitude and frequency of contractions are low during the luteal phase [1], and a gradual increase in contractile amplitude and frequency ouccrs concomitant with a rapid decrease in the progesterone (P4) level [2]. Both contractile amplitude and frequency reach their maximal values during estrus, and the values quickly diminish over the next 3 days [1,2].Angiotensin (Ang) II, the major bioactive peptide of the reninangiotensin system, is involved in autocrine/paracrine regulation of the oviduct [3]. It is a vasoactive peptide that is converted from Ang I by angiotensin-converting enzyme-1 (ACE-1). Ang I is produced from the precursor angiotensinogen by the enzymatic activity of renin. Expression of Ang II and Ang II receptor (Ang II-R) in the human fallopian tube has been demonstrated [4], and Ang II plays a role in regulating the composition of fallopian tube secretions [5]. We recently reported that Ang II is secreted by the bovine oviduct and stimulates oviductal contractions [6][7][8]. Indeed, in the bovine oviduct, Ang II stimulates release of prostaglandin E2 (PGE2), prostaglandin F2α (PGF2α), and endothelin-1 (ET-1), which are the predominant inducers of contractions [9][10][11]. Moreover, luteinizing hormone (LH) stimulates e production and release of these hormones by the bovine oviduct during this period, and estradiol-17β (E2) exert...