Real-time dynamics of prostaglandin F2α release from uterus and corpus luteum during spontaneous luteolysis in the cow

Abstract

Prostaglandin (PG) F2α released from the uterus in a pulsatile fashion is essential to induce regression of the corpus luteum (CL) in the cow. In addition to the uterus, the CL has also been recognized as a site of PGF2α production. Therefore, this study aimed to determine the detailed dynamics of the releasing profile of CL-derived PGF2α together with uterus-derived PGF2α during spontaneous luteolysis in the cow. Non-lactating Holstein cows (n = 6) were surgically implanted with a microdialysis system (MDS) on day 15 (oestrus = day 0) of the oestrous cycle. Simultaneously, catheters were implanted to collect ovarian venous plasma ipsilateral to the CL as well as jugular venous plasma. The concentrations of PGF2α, 13,14-dihydro-15-keto-PGF2α (PGFM) and progesterone in the MDS and plasma samples were determined by enzyme immunoassays. The intra-luteal PGF2α secretion slightly increased after the onset of luteolysis (0 h) and drastically increased from 24 h, and was maintained at high levels towards the following oestrus. Furthermore, PGF2α was released from the CL into the ovarian vein in a pulsatile manner during spontaneous luteolysis. Also, the fact that intra-luteal secretion of PGF2α and PGFM showed a positive correlation indicates the existence of a local metabolic pathway for PGF2α in the CL. In conclusion, the present study clarified the real-time dynamics of uterus-derived PGF2α and CL-derived PGF2α during spontaneous luteolysis in the cow, and gives the first in vivo evidence that the CL releases PGF2α during spontaneous luteolysis in the cow. Although the physiological relevance of CL-derived PGF2α appears to be restricted to a local role as an autocrine/paracrine factor in the CL, overall results support the concept that the local release of PGF2α within the regressing CL amplifies the luteolytic action of PGF2α from the uterus.