Luteotropic mechanisms in the bovine corpus luteum: Role of oxytocin, prostaglandin f_2α, progesterone and noradrenaline

The main function of the corpus luteum (CL) is production of progesterone (P4). Adequate luteal function to secrete P4 is crucial for determining the physiological duration of the estrous cycle and for achieving a successful pregnancy. The bovine CL grows very fast and regresses within two days at luteolysis. The mechanism controlling the development and secretory function of the bovine CL may involve many factors that are produced both within and outside the CL. Some of these regulators seem to be prostaglandins (PGs), oxytocin (OT) and adrenergic factors such as noradrenaline (NA). Recently, there has been some evidence that P4 acts within the bovine CL as an autocrine and/or paracrine regulator. Each of these factors may act on the CL independently or may modify the actions of others. The purpose of this paper is to review and discuss the possible roles of OT, PGs, P4 and NA as luteotropic auto/paracrine regulators in the bovine CL. Furthermore, intraluteal mechanisms controlling the sensitivity of the CL to extragonadal PGF_2α are discussed.