TNFa and IL-1p were shown to stimulate P4 secretion in the isolated rat ovary perfused in vitro and in a rat follicle culture, whereas they did not exert any clear effect on basal or LH-stimulated P4 production in the present MDS study. Our data are partly comparable with the results of a study of porcine theca cells in which TNF-a did not affect basal secretion of P4 from the cells but caused a marked dose-dependent inhibition of LH-stimu-lated P4 production. As the present data are the first on the effects of cytokines in an MDS study in the bovine follicle, a detailed evaluation of these effects must await an accumulation of data from different systems of bovine follicles, rather than from other species.
Theca cells in the preovulatory follicle have been demonstrated to release prostaglandin upon cytokine stimulation in vitro. The present MDS study demonstrated that LH increased local ET-1 release from the theca layer and that ET-1 stimulation after LH exposure induced a further PGE2 release. These results strongly suggest that ET-1 locally regulates the LH-triggered ovulatory process. ET-1 and PGE2 could possibly act synergistically to control blood flow, modify vascular permeability, and activate proteolytic enzymes involved in follicular rupture. LH-induced PGE2 release was amplified also by TNFa. This local increase in PGE2 may modulate collagenolytic activity and hemodynamic changes associated with the ovulatory process. levitra super active plus
In conclusion, ET-1 is released from the theca layer of mature bovine follicles in vitro and affects follicular steroids and PGE2 secretion. The overall results suggest that interactions among ET-1, PGE2, and cytokines may play key roles in a local intermediatory/amplifying system of the LH-triggered ovulatory cascade in the bovine preovulatory follicle.