OBJECTIVETo investigate the expression changes and regulation of pituitary adenylate cyclase-activating polypeptide (PACAP) mRNA in corpus luteum during pregnancy.

METHODSPregnant rats' ovaries were collected at different time points. The techniques of RT-PCR and in situ hybridization were used to observe expression changes of PACAP mRNA in rat ovaries during pregnancy. To further explore the regulation mechanism of PACAP mRNA expression in corpus luteum, luteal cells were cultured in vitro. Immature (25 - 28 days old) female Sprague-Dawley rats were injected subcutaneously with 50IU pregnant mare serum gonadotrophin (PMSG), and 25IU human chorionic gonadotrophin (hCG) 48 h later, to induce follicular development and luteum formation. On day 6 after hCG administration (the day of hCG administration was the first day), the rats were killed by guillotine and the ovarian luteal cells were collected. After incubation for 24 h, luteal cells were administration with various factors for 24 h. And then expression changes of PACAP mRNA in luteal cells after administration with different factors were detected by RT-PCR, and radioimmunoassay was used to analyze progesterone levels.

RESULTSWith the development of pregnancy, the expression of PACAP mRNA increased gradually, reached the peak at pregnancy 19 d, and then decreased. Compared with control group, platelet activating factor (PAF), forskolin and PMA could obviously stimulate PACAP mRNA expression in luteal cells which were cultured with corresponding factors for 24 h. At the same time, progesterone levels in culture media were also elevated.

CONCLUSIONPACAP, acting as a local ovary regulator, was closely related to the maintenance of medium-term and late pregnancy. PAF could directly stimulate PACAP mRNA expression in luteal cells, and protein kinase C (PKC) and protein kinase A (PKA) signal pathways could both participate in this process.