Expression of oxytocin receptors is greatly reduced in the placenta of heavy mares with retained fetal membranes due to secondary uterine atony

Rapacz-Leonard, A.; Raś, A.; Całka, Jarosław; Janowski, Tomasz

doi:10.1111/evj.12426

Cited by 15 publications

(8 citation statements)

References 31 publications

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“…Our present results differ from those of our previous study of the placenta in horses, in which we observed substantially less OXTR content in FMR associated with secondary atony of the uterus than in physiological parturition 27 . The difference between studies is attributable to two factors: first, the FMR horses in our present study did not have secondary atony of the uterus.…”

Section: Discussioncontrasting

confidence: 99%

“…OXT exerts its effects by binding with its receptor (OXTR), which is expressed in the myometrium, mammary gland, and placenta 23 . During pregnancy and parturition in horses, OXTR has only been studied in the nonpregnant uterus, the endometrium in early pregnancy (<21 days) 16,25,26 , and the endometrium and allantochorion within 3 hours of foal delivery 27 . Thus, OXTR levels in the horse placenta during the majority of pregnancy and parturition remain unknown.…”

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confidence: 99%

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The oxytocin-prostaglandins pathways in the horse (Equus caballus) placenta during pregnancy, physiological parturition, and parturition with fetal membrane retention

Rapacz-Leonard

Leonard

Chmielewska-Krzesińska

et al. 2020

Sci Rep

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Despite their importance in mammalian reproduction, substances in the oxytocin-prostaglandins pathways have not been investigated in the horse placenta during most of pregnancy and parturition. Therefore, we quantified placental content of oxytocin (OXT), oxytocin receptor (OXTR), and prostaglandin E2 and F2 alpha during days 90-240 of pregnancy (PREG), physiological parturition (PHYS), and parturition with fetal membrane retention (FMR) in heavy draft horses (PREG = 13, pHYS = 11, FMR = 10). We also quantified OXTR and prostaglandin endoperoxide synthase-2 (PTGS2) mRNA expression and determined the immunolocalization of OXT, OXTR, and PTGS2. For relative quantification of OXT and OXTR, we used western blotting with densitometry. To quantify the prostaglandins, we used enzyme immunoassays. For relative quantification of OXTR and PTGS2, we used RT-qPCR. For immunolocalization of OXT, OXTR, and PTGS2, we used immunohistochemistry. We found that OXT was present in cells of the allantochorion and endometrium in all groups. PTGS2 expression in the allantochorion was 14.7-fold lower in FMR than in PHYS (p = 0.007). These results suggest that OXT is synthesized in the horse placenta. As PTGS2 synthesis is induced by inflammation, they also suggest that FMR in heavy draft horses may be associated with dysregulation of inflammatory processes. In the placenta, a delicate balance of hormones helps to support pregnancy and initiate parturition 1-3. Parturition is a proinflammatory event 4-8 , and delivery of the fetus and the placenta are accompanied by coordinated contractions, pain, and swelling, which are mostly mediated by prostaglandins 9. Exposure of the placenta to endogenous or exogenous oxytocin (OXT) causes it to release prostaglandin E2 (PGE 2) and prostaglandin F2 alpha (PGF 2ɑ) within a few hours 10-21 (see Supplementary Fig S1 for the pathways that start with OXT release and end with the prostaglandins binding to their receptors). OXT is released from the posterior pituitary gland 22 , and during pregnancy and parturition in humans, from the placenta 23. Given that, of all domestic and laboratory species, horses may be the most similar to humans in terms of the endocrinology of pregnancy and parturition 24 , it seems likely that horses also release OXT from the placenta. Moreover, human placental OXT is not believed to play a role in myometrial contractions, unlike pituitary OXT 13. Thus, it seems likely that horse placental OXT would be a signal for prostaglandin release in the placenta itself, and not a signal for myometrial contractions. However, the presence of OXT in horse placental cells needs to be verified.

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Section: Discussioncontrasting

confidence: 99%

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confidence: 99%

The oxytocin-prostaglandins pathways in the horse (Equus caballus) placenta during pregnancy, physiological parturition, and parturition with fetal membrane retention

Rapacz-Leonard

Leonard

Chmielewska-Krzesińska

et al. 2020

Sci Rep

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“…; Threlfall ; O'Brien ; Rapacz‐Leonard et al . ). Stillbirths and a lack of nursing and oxytocin release may also contribute to the presence of a retained placenta.…”

Section: Retained Placentamentioning

confidence: 97%

Equine placenta – A clinician's perspective. Part 2: Abnormalities

Pozor

2015

Equine Veterinary Education

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Summary Any insufficiency of the equine placenta has dramatic effects on the developing equine fetus. Placental abnormalities, such as the separation of the chorioallantois from the maternal endometrium or torsion of the umbilical cord, lead to fetal demise, premature labour or abortion. These conditions are each associated with characteristic lesions on the equine placenta, which can be found during a detailed examination. These findings can be very helpful for diagnosing problems and implementing appropriate treatments for mares and affected newborn foals. Furthermore, the retention of the entire placenta or any small fragment thereof can cause metritis, laminitis and sepsis. The prompt diagnosis and aggressive treatment of this condition is necessary to save the mare from becoming seriously ill. Therefore, a thorough evaluation of the equine placenta is a crucial element of the post partum evaluation of every brood mare.

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“…Mares experiencing secondary uterine atony have decreased oxytocin receptor expression in the endometrium and allantochorion, reducing the likelihood of successful expulsion of FM with oxytocin therapy alone (Rapacz‐Leonard et al . ). This increases the indication for manual removal of FM in cases of secondary uterine atony, as oxytocin therapy is less likely to be successful.…”

Section: Discussionmentioning

confidence: 97%

In the mare, does manual removal of fetal membranes negatively affect fertility?

Platt

Walker

Gunn

2019

Equine Veterinary Education

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Expression of oxytocin receptors is greatly reduced in the placenta of heavy mares with retained fetal membranes due to secondary uterine atony

Abstract: Inadequate expression of oxytocin receptors may be a cause of uterine atony leading to fetal membrane retention.

Cited by 15 publications

References 31 publications

The oxytocin-prostaglandins pathways in the horse (Equus caballus) placenta during pregnancy, physiological parturition, and parturition with fetal membrane retention

The oxytocin-prostaglandins pathways in the horse (Equus caballus) placenta during pregnancy, physiological parturition, and parturition with fetal membrane retention

Equine placenta – A clinician's perspective. Part 2: Abnormalities

In the mare, does manual removal of fetal membranes negatively affect fertility?

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