Positive Association, in Local Release, of Luteal Oxytocin with Endothelin 1 and Prostaglandin F2alpha During Spontaneous Luteolysis in the Cow: A Possible Intermediatory Role for Luteolytic Cascade Within the Corpus Luteum1

Abstract

Luteolysis is caused by a pulsatile release of prostaglandin F(2alpha) (PGF(2alpha)) from the uterus in ruminants, and a positive feedback between endometrial PGF(2alpha) and luteal oxytocin (OXT) has a physiologic role in the promotion of luteolysis. The bovine corpus luteum (CL) produces vasoactive substances, such as endothelin 1 (EDN1) and angiotensin II (Ang II), that mediate and progress luteolysis. We hypothesized that luteal OXT has an additive function to ensure the CL regression with EDN1 and Ang II, and that it has an active role in the luteolytic cascade in the cow. Thus, the aim of the present study was to observe real-time changes in the local secretion of luteal OXT and to determine its relationship with other local mediators of luteolysis. Microdialysis system (MDS) capillary membranes were implanted surgically into each CL of six cyclic Holstein cows (18 lines total among the six cows) on Day 15 (estrus == Day 0) of the estrous cycle. Simultaneously, catheters were implanted to collect ovarian venous plasma ipsilateral to the CL. Although the basal secretion of OXT by luteal tissue was maintained during the experimental period, the intraluteal PGF(2alpha) secretion gradually increased up to 300% from 24 h after the onset of luteolysis (0 h; time in which progesterone started to decrease). In each MDS line (microenvironment) within the CL, the local releasing profiles of OXT were positively associated with PGF(2alpha) and EDN1 within the CL in all 18 MDS lines implanted in the six CLs (OXT vs. PGF(2alpha), 50.0%; OXT vs. EDN1, 72.2%; P < 0.05). On the other hand, the intraluteal OXT was weakly related to Ang II (OXT vs. Ang II, 27.7%). In the ovarian vein, the peak concentration of PGF(2alpha) increased significantly when the peak of PGF(2alpha) coincided with the peak of OXT after the onset of spontaneous luteolysis (P < 0.05). In conclusion, intraluteal OXT may locally modulate secretion of vasoactive substances, particularly EDN1 and PGF(2alpha) within the CL, and thus might be one of the luteal mediators of spontaneous luteolysis in the cow.

Effect of oxytocin infusion on luteal blood flow and progesterone secretion in dairy cattle

“…This could explain why there was a tendency for P4 concentrations to increase in the present study, since the CLs of some cows were still sensitive to OXY while others were not. Shirasuna et al [23] recently confirmed this dual role of luteal OXY as luteotropic (during the early luteal and mid-luteal phases) and luteolytic (during the late luteal phase after initiation of the luteolytic cascade), highlighting the modulatory effect of OXY on local secretion of vasoactive substances within the CL.…”

Reversible infertility in a liver receptor homologue-1 (LRH-1)-knockdown mouse model

“…Other genes that showed high downregulation were previously described to be involved in: (1) (Table 1) and Oxtr (Shirasuna et al 2007) and Prlr (Le et al 2012; see Fig. S1 and Table S1); (2) proliferation, cell cycle and apoptosis, namely Btc (Oh et al 2011), Rasl10a (Elam et al 2005), Dpysl4 (Kimura et al 2011), Sfrp4 (Jacob et al 2012), Dusp1 (Chen et al 2011) and Rcc2 (Grigera et al 2012); and (3) neuronal processes, namely Nmu (Chu et al Regulator of chromosome condensation 2 À2.5*** À2.4*** Sh2d4a SH2 domain containing 4A À2.5* À2.2* Table 2.…”

Endothelins in regulating ovarian and oviductal function

“…Interestingly, peripheral concentrations of EDN1 continued to rise well after the demise of the CL with concentrations of this peptide peaking around the time of estrus. In a later study by Shirasuna et al (63), microdialysis (MDS) lines were implanted into the corpora lutea of naturally cycling cows and the local release of several hormones of interest, including EDN1, determined during spontaneous luteolysis. These authors observed a pulsatile pattern in the local release of EDN1 by the regressing CL, truly suggestive of a regulated, physiological role.…”