Leukotrienes are auto-/paracrine factors in the bovine corpus luteum: an in vitro study

The aim of this study was to determine leukotrienes (LTs) functions in the bovine corpus luteum (BCL) during the oestrous cycle. In steroidogenic CL cells we examined the effect of luteotropic [LH, prostaglandin E(2) (PGE(2))] and luteolytic (PGF(2α), cytokines) factors on: the levels of LTB(4) and C(4), the expression of 5-lipoxygenase (LO), LT receptors type I (LTR-I) and LTR-II, and the effects of LTB(4) and C(4) stimulations on the levels of progesterone (P4), PGE(2), F(2α) and nitric oxide (NO) metabolites. Both luteolytic and luteotropic factors stimulated 5-LO expression on days 2-4 and 17-19 of the cycle. Leukotriene receptors type I expression increased after PGE(2) and tumour necrosis factor α with interferon γ (TNF/IFN) stimulation on days 2-4 of the cycle. Leukotriene receptor type II expression increased after PGE(2α) and TNF/IFN stimulation on days 2-4 and 17-19 of the cycle, and LTR-II expression on days 8-10 of the cycle was unchanged after cell stimulation with any factor. Leukotriene B(4) level increased after BSC incubation with luteotropic factors during all examined days of the cycle and after cytokine stimulation at early- and mid-luteal stages, whereas luteolytic factors stimulated LTC(4) secretion over the entire cycle. Leukotriene B(4) stimulated P4 secretion at the mid-luteal stage and stimulated NO secretion during all examined phases. Leukotriene B(4) stimulated PGE(2) secretion at the early- and mid-luteal stage. Leukotriene C(4) inhibited P4 secretion at the mid- and regressing-luteal stage, stimulated NO (entire cycle) and PGF(2α) at mid- and regressing-luteal phases. Leukotrienes modulate steroidogenic cells functions, depending on the stage of the cycle. Leukotriene B(4) plays a luteotropic role stimulating P4 and PGE(2) secretions; LTC(4) stimulates the secretion of luteolytic factors and enhances the luteolytic cascade within BCL.