Nuclear progesterone receptor regulates blood coagulation facilitating ovulation in zebrafish

Ovulation is a remodeling process including blood capillary rupture and coagulation. Until now, there is no regulation and functional studies of coagulation factors in ovulation. Here, we report dramatic increases of coagulation factors (f5, f3a) in zebrafish preovulatory follicles. This upregulation was induced by progestin (DHP: 17α, 20β-dihydroxy-4-pregnen-3-one), a native ligand for nuclear progestin receptor (Pgr) that is essential for ovulation in zebrafish; but was abolished in pgr-/-. In addition, promoter activities of f5 and f3a were significantly enhanced by progestin via zebrafish Pgr. Similarly, we found promoter activities of human F5 were significantly stimulated by progesterone (P4) via human PGRB. Moreover, a dramatic increase of erythrocyte numbers in capillaries on ovarian follicles was associated with ovulation. Importantly, heparin, an anticoagulant, inhibited ovulation. Furthermore, reduced fecundity and impaired ovulation were observed in f5+/- female zebrafish. Together, our results provide plausible evidence for an exceptional function of coagulation factors in ovulation.

Characterization of Nuclear Progesterone Receptor Isoforms in the Term Equine Placenta

In equine parturition, the role of progestins along with the nuclear progesterone receptor (nPR) signaling pathway in the placenta is not completely clarified. The progestins play an integral role in maintaining myometrial quiescence during the late stage of pregnancy via acting on nPR isoforms (PRA and PRB; PRB is more active than PRA). The current study aimed to determine the PRA and PRB expressions in the term equine placenta at the gene and protein levels. Six term equine placentas were used in this study. Reverse transcription polymerase chain reaction (RT-PCR) was used to quantify the mRNA expression for PRA and PRB. The protein expression was detected using the Western Blot technique. The results revealed that the mRNA and protein expressions for PRA were significantly higher (P < 0.0001) in the term equine placental tissue compared to the mRNA and protein expressions of PRB. These results demonstrated that nPRs are detectable in the term placenta of mares and PRA is the dominant isoform expressed. The present findings raised the possibility that the PRA plays an important role in the parturition process and expulsion of the placenta in mares.