Intraluteal Release of Progesterone and Prostaglandins during PGF2.ALPHA.-Induced Luteolysis in Ewes: Local Effects of Tumor Necrosis Factor-.ALPHA..

Abstract

Abstract. The role of tumor necrosis factor-α (TNF-α) in the local regulatory mechanisms of functional luteolysis in the ewe was examined. TNF-α was infused into a microdialysis system (MDS) implanted in the corpus luteum (CL) for 24 h from 2 h after the intramuscular injection of cloprostenol (defined as 0 h), and plasma as well as intraluteal changes of progesterone (P) and prostaglandins (PG) were observed. Three ewes were treated for superovulation, and multiple CL formed thereafter were surgically implanted with the MDS (1 line/CL) on Day 7 after GnRH injection. Serial fractions from the MDS were collected every 30 min for 40 h on Days 9-11 following a preperfusion period of 30 h. An intramuscular injection of cloprostenol stimulated an acute increase of plasma P concentration (an increase to 150%) within 1 h, followed by a rapid decrease within 6 h (P<0.05), which directly correlates with functional luteolysis. Intraluteal P release into the MDS showed a profile similar to that in the plasma, but significantly decreased from 17 h (P<0.05). Twenty-four-hour infusions of TNF-α at 20 ng/ml and 200 ng/ml into the MDS starting at 2 h after cloprostenol injection slightly hastened the time of onset of P decrease when they were compared with the time of the control. In contrast, the higher dose of TNF-α at 2000 ng/ml clearly delayed the time of onset of P decrease. Intraluteal release of PGF2α and PGE2 in the control was slightly increased between 18-32 h (P<0.05). A 26-h infusion with indomethacin partly blocked the increase in basal release of both PG (P<0.05), whereas it had no effect on the P release. A 24-h infusion with different concentrations of TNF-α stimulated the release of PGE2, but not the release of PGF2α (P<0.05). The results support the idea that TNF-α may have a passive or secondary role in functional luteolysis. Furthermore, the intraluteal PG production appears to have no direct correlation with functional luteolysis.

Direct Effect of PGF2.ALPHA., TPA and lonophore A23187 on Progesterone Release from Microdialyzed Corpus Luteum inthe Cow.

“…Although the functional similarity between intact cyclic CL and the CL formed after superovulation is controversial, it is well known that an intramuscular injection of PGF2α (or its analogue) to such a superovulated cow clearly induces complete luteolysis that is well comparable with PGF2α-induced luteolysis in the cyclic cow. Therefore, we believe that the basic local mechanisms involved in PGF2α-induced luteolysis in both models are very similar [10].…”

Local interaction of prostaglandin F2α with endothelin-1 and tumor necrosis factor-α on the release of progesterone and oxytocin in ovine corpora lutea in vivo: a possible implication for a luteolytic cascade

“…After a period of 8 h for observing the spontaneous release of progesterone (baseline), further fractions were collected according to the experimental design. The transfer capacity of the microdialysis membrane was about 0.1% of the concentration infused as determined for OT, ET-1 and TNFa, and about 1% for progesterone and PGF 2a under the conditions used (Miyamoto et al 1997(Miyamoto et al , 1998a. At the end of the experiments, the ewes were ovariectomized, and the CL were fixed in Bouin's solution, dehydrated in a graded series of ethanol, cleared in xylene and embedded in paraffin wax, and then processed for histology after hematoxylin -eosin staining.…”

“…The study used a multiple CL model to implant the MDS, as the CL formed after super-ovulation were shown to regress in response to a luteolytic injection of PGF 2a in a way that was very similar to that of intact CL (Miyamoto et al 1998a). This model enables us to examine in parallel several experimental infusions into the MDS implanted in the different CL (one MDS line/CL) within a ewe (Miyamoto et al 1998a,b The experiments were conducted in October to December, during the breeding season.…”

Ovarian activity, hormone profile, pro‐inflammatory cytokines and reproductive performance of buffalo cows fed diets with different estrogenicity

“…This inflammation-inducing factor has been suggested to serve as a mediator of the luteolytic action of PGF 2α within the CL (Ohtani et al, 2004). In the ovine CL, TNF-α interacts with PGF 2α and endothelin-1 and together they directly inhibit local P 4 release (Miyamoto et al, 1998). During luteolysis, TNF-α can act locally within the bovine CL in concert with other cytokines inducing apoptosis and regression of the CL.…”