Expression of oxytocin receptor in human pregnant myometrium.

Abstract

Around the onset of labor, uterine sensitivity to oxytocin (OT) increases tremendously. Although this is considered to reflect OT receptor (OTR) augmentation in myometrium, neither spatial expression of OTR nor the level of the receptor message during the course of pregnancy have been investigated at the molecular level. We examined the localization and expression of the OTR in human myometrium by means of in situ hybridization, immunohistochemistry, and Northern and Western blotting. In the term pregnant myometrium, OTR expressing smooth muscle cells are observed diffusely and heterogeneously. Some of the smooth muscle cells were expressed high levels of the receptor at the messenger RNA and protein level, and they were surrounded with cells weakly positive for the OTR or negative. The level of OTR transcripts increased according to the course of pregnancy. The receptor messenger RNA level reached over 300-fold at parturition compared with the nonpregnant myometrium. In the myometrium at 32 weeks of gestation and not in labor, a relatively large amount (about 100-fold) of the receptor message was expressed. In the nonpregnant myometrium, significant amount of the receptor protein was revealed by Western blotting. We also found that the receptor protein was augmented at term and after the onset of labor. These findings indicated that the expression of OTR changes dynamically at the transcription and protein level during pregnancy and that its expression is heterogeneous in the term myometrium.

Prostaglandin F2α regulates the expression of uterine activation proteins via multiple signalling pathways

“…Oxytocin is a well-known neurohypophysial hormone that facilitates parturition and is commonly used as an uterotonic drug in clinical practice for the treatment of primary postpartum haemorrhage. Many studies have demonstrated that OTR level in myometrium is much higher at the end of pregnancy, which is critical for the onset of labour (Fuchs et al 1995, Kimura et al 1996, Challis et al 2000 although a few studies reported that OTR expression is not increased with labour (Phaneuf et al 2000, Havelock et al 2005. This study confirmed the previous findings that PGF2A upregulates the expression of these proteins in human pregnant myometrium, suggesting that PGF2A is involved in the processes of uterus activation for labour.…”

Possible roles of oxytocin receptor and vasopressin-1α receptor in the pathomechanism of dysperistalsis and dysmenorrhea in patients with adenomyosis uteri

“…Earlier studies have reported that OT (37) and its receptor are expressed in normal human endometrial and myometrial cells (12,(36)(37)(38)(39)(40). In addition, a role of OTR and VPR in the pathogenesis of dysmenorrhea and development of dyscontractile disorders have also been supported (7,8,41).…”

Myometrial cytokines and their role in the onset of labour

“…It is a key regulator of myometrial function. Its expression increases with advancing gestation (Fuchs et al 1991), peaking in early labour (Rivera et al 1990), corresponding to the clinical observation of increased uterine sensitivity to OT (Kimura et al 1996). OT increases myometrial contractility via increases in intracellular calcium, mediated through its G-protein-coupled receptor, OTR.…”