Leukotrienes modulate secretion of progesterone and prostaglandins during the estrous cycle and early pregnancy in cattle: An in vivo study

Abstract

Recently, we showed that leukotrienes (LTs) regulate ovarian cell function in vitro. The aim of this study was to examine the role of LTs in corpus luteum (CL) function during both the estrous cycle and early pregnancy in vivo. mRNA expression of LT receptors (BLT for LTB4 and CYSLT for LTC 4), and 5-lipoxygenase (5-LO) in CL tissue and their localization in the ovary were studied during the estrous cycle and early pregnancy. Moreover, concentrations of LTs (LTB4 and C4) in the CL tissue and blood were measured. 5-LO and BLT mRNA expression increased on days 16-18 of the cycle, whereas CYSLT mRNA expression increased on days 16-18 of the pregnancy. The level of LTB4 was evaluated during pregnancy compared with the level of LTC4, which increased during CL regression. LT antagonists influenced the duration of the estrous cycle: the LTC4 antagonist (azelastine) prolonged the luteal phase, whereas the LTB4 antagonist (dapsone) caused earlier luteolysis in vivo. Dapsone decreased progesterone (P4) secretion and azelastine increased P4 secretion during the estrous cycle. In summary, LT action in the bovine reproductive tract is dependent on LT type: LTB4 is luteotropic during the estrous cycle and supports early pregnancy, whereas LTC4 is luteolytic, regarded as undesirable in early pregnancy. LTs are produced/secreted in the CL tissue, influence prostaglandin function, and serve as important factors during the estrous cycle and early pregnancy in cattle. © 2010 Society for Reproduction and Fertility.