Natriuretic peptide system regulation in granulosa cells during follicle deviation and ovulation in cattle.

Contents: Natriuretic peptides (NPs) are known to regulate reproductive events in polyovulatory species, but their function and regulation in monovulatory species remain to be fully characterized. Using a well‐established in vivo model, we found that bovine granulosa cells from follicles near the deviation stage express mRNA for the three NP receptors (<italic>NPR1</italic>,<italic> NPR2</italic> and <italic>NPR3</italic>), but not for NP precursors (<italic>NPPA</italic>,<italic> NPPB</italic> and <italic>NPPC</italic>). The abundance of <italic>NPR3 </italic>mRNA was higher in dominant compared to subordinate follicles at the expected time of follicular deviation. After deviation, mRNA for all NP receptors was significantly more abundant in the dominant follicle. Intrafollicular inhibition of oestrogen receptors downregulated <italic>NPR1 </italic>mRNA in dominant follicles. In granulosa cells from preovulatory follicles, <italic>NPPC</italic> mRNA increased at 3 and 6 h after systemic GnRH treatment, but decreased at 12 and 24 h to similar levels observed in samples collected at 0 h. After GnRH treatment, <italic>NPR1 </italic>mRNA was upregulated at 24 h, <italic>NPR3 </italic>mRNA gradually decreased after 3 h, while <italic>NPR2 </italic>mRNA was not regulated. The mRNA expression of the enzyme <italic>FURIN</italic> increased at 24 h after GnRH treatment. These findings revealed that the expression of mRNA encoding important components of the NP system is regulated in bovine granulosa cells during follicular deviation and in response to GnRH treatment, which suggests a role of NP system in the modulation of these processes in monovulatory species. [ABSTRACT FROM AUTHOR]