Prostaglandin F2.ALPHA. Increases Lipoprotein Utilization for Progesterone in Bovine Early Corpora Lutea In Vitro.

Abstract

Luteal cells utilize lipoproteins (LIPs) for progesterone (P) synthesis. A luteolysin prostaglandin F2α (PGF 2α) has shown to prevent the LIPs utilization for steroidogenesis in bovine midcycle luteal cells. However, a luteolytic injection of PGF2α before Day 5 (Day 0=estrus) can not induce the regression of the corpus luteum (CL). This suggests that the intraluteal mechanism of PGF2 α action on the LIPs utilization in early CL is different from that of the mid luteal stage. Thus, this study aimed to investigate the interaction between PGF2 α and LIPs on the secretion of P and oxytocin (OT) from bovine early CL. An in vitro microdialysis system (MDS) was used as a model. Each bovine early CL (Days 3-4) was implanted with the MDS, and maintained in an organ culture chamber. The infusion of LIPs (1 μg/ml) stimulated P release during infusion, but had no effect on OT release. The infusion of PGF2α (10-5 M) stimulated both P and OT release during infusion. When LIPs were infused after PGF2α exposure, P and OT release continued to be stimulated until 3 h thereafter. The results show that PGF2α is capable of enhancing the LIPs utilization in early CL, thus support the concept that luteal PGF2α acts as a luteotropic promoter in bovine early CL.