Effects of pregnancy and systemic or intrauterine oxytocin infusion on the distribution of endometrial oxytocin receptors in the ewe: an autoradiographic study

1993 ◽  
Vol 137 (3) ◽  
pp. 423-NP ◽  
Author(s):  
V. J. Ayad ◽  
T. J. Parkinson ◽  
E. L. Matthews ◽  
M. L. Wild
Keyword(s):  
Epithelial Cells ◽  
Stromal Cells ◽  
Autoradiographic Study ◽  
Oxytocin Receptor ◽  
Oestrous Cycle ◽  
Oxytocin Receptors ◽  
Receptor Concentration ◽  
Oxytocin Infusion ◽  
Luminal Epithelial Cells ◽  
Specific Labelling

ABSTRACT Previous autoradiographic studies have suggested that the regulation of oxytocin receptors differs between endometrial cell types during the ovine oestrous cycle, and that those present on luminal epithelial cells are of particular importance to the regulation of prostaglandin F2α release during luteal regression. The present autoradiographic study compares the distribution of the endometrial oxytocin receptor in day-15 non-pregnant and pregnant ewes. The distribution of the endometrial oxytocin receptor in day-15 non-pregnant ewes infused with systemic or intrauterine oxytocin has also been investigated. Continuous, s.c. infusion of oxytocin (150 mmol/24 h) into ewes (n = 6) between days 10 and 15 of the oestrous cycle significantly increased plasma oxytocin concentrations (to approximately 100 pmol/l). There was no similar increase in systemic oxytocin concentrations in ewes receiving intrauterine (i.u.) oxytocin infusions (10 nmol/24 h) between days 10 and 15 of the oestrous cycle (n = 6). Luteolysis was inhibited in all six animals infused with oxytocin (s.c.) and endometrial oxytocin receptor concentrations were significantly lower on day 15 in these animals (12·8 ± 6·5 (s.e.m.) fmol/mg protein; P<0·001) and in pregnant ewes (18·4 ± 15·4 fmol/mg protein; P <0·001; n = 8) than in ewes infused with saline (248·6±67·1 fmol/mg protein; n = 6). While the 125I-labelled oxytocin receptor antagonist, [1-(β-mercapto-β,β-cyclopentamethylene propionic acid), 2-(ortho-methyl)-Tyr2, Thr4, Orn8, Tyr9-NH2]-vasotocin (125I-labelled OTA) clearly labelled glandular epithelia, luminal epithelium and caruncular stromal cells specifically on day 15 in saline (s.c.)-infused ewes, such specific labelling appeared to be reduced or absent from pregnant animals and those infused with oxytocin (s.c.). A significant reduction in the density of labelling of caruncular stroma (P < 0·05) and luminal epithelium (P < 0·001) was confirmed using quantitative densitometric analysis. The reduction in the labelling of endometrium in oxytocin-infused ewes was not caused by the binding of exogenous oxytocin to endometrial binding sites. Oxytocin infusion (i.u.) did not inhibit luteolysis, nor was there any significant difference in the endometrial oxytocin receptor concentration in this group of ewes on day 15 compared with those infused with saline (i.u.). There was also clear specific labelling of luminal epithelial cells with 125I-labelled OTA in ewes receiving oxytocin infused i.u. and quantification of autoradiograms failed to differentiate between these animals and those infused with saline (i.u.). It was concluded that systemic oxytocin infusion and the early establishment of pregnancy led to a clear reduction in the endometrial oxytocin receptor concentration on luminal epithelial cells, glandular epithelial cells and caruncular stromal cells, but that i.u. oxytocin infusions did not affect any of these receptor populations and notably not the luminal epithelial oxytocin receptor. The results support the contention that the luminal epithelial oxytocin receptor is involved in the luteolytic process. Journal of Endocrinology (1993) 137, 423–431

Autoradiographic localization of oxytocin receptors in the endometrium during the oestrous cycle of the ewe

1991 ◽  
Vol 130 (2) ◽  
pp. 199-NP ◽  
Author(s):  
V. J. Ayad ◽  
E. L. Matthews ◽  
D. C. Wathes ◽  
T. J. Parkinson ◽  
M. L. Wild
Keyword(s):  
Epithelial Cells ◽  
Stromal Cells ◽  
Oxytocin Receptor ◽  
Oestrous Cycle ◽  
Luminal Epithelium ◽  
Tissue Samples ◽  
Luteal Regression ◽  
Oxytocin Receptors ◽  
Secretory Glands ◽  
Luminal Epithelial Cells

ABSTRACT The present study was designed to determine the localization of the endometrial oxytocin receptor during the ovine oestrous cycle, particularly on day 14, the time of initiation of luteal regression in the ewe. Samples were obtained from 29 ewes at different stages of the oestrous cycle (several during the luteal phase and on every day between day 14 (− 2) and day + 3 of the oestrous period). Oxytocin receptors were localized autoradiographically in sections of uterine tissue, using the 125I-labelled oxytocin receptor antagonist [1-(β-mercapto-β,β-cyclopentamethylene propionic acid), 2-(ortho-methyl)-Tyr2,Thr4,Orn8,Tyr9-NH2]-vasotocin (125I-labelled OTA). There was some variation in the pattern of 125I-labelled OTA labelling between different uterine tissue samples from the same ewe and also between samples obtained from different ewes thought to be at the same stage of the oestrous cycle. A clear overall pattern did, however, emerge with 125I-labelled OTA-binding sites distributed between luminal epithelial cells, glandular epithelial cells and caruncular stromal cells to varying extents on different days of the cycle. During the luteal phase (days 5–12) clear specific labelling of endometrial tissue was generally absent. On day 14 labelling was evident on the luminal epithelium, but only in nine tissue samples out of a total of 18 studied, indicating that the entire luminal surface did not contain oxytocin receptors at this time. Between the day before oestrus and day 3 of the oestrous cycle the luminal epithelium was consistently labelled. The most extensive labelling of the remaining endometrial tissue was observed on the day of oestrus, with 125I-labelled OTA-binding sites clearly present on the stromal cells within caruncles and on a large proportion of secretory epithelia. This contrasted with the day before and the day after oestrus when labelling of glandular tissue was confined to the superficial endometrium, and labelling of caruncular stromal cells, although sometimes evident, was never as intense as on day 0. On days 2 and 3 labelling varied between being similar to that found on day 1 and being confined to the luminal epithelium and very few superficial secretory glands. The results of this study lead us to conclude that the oxytocin receptor shows a differential distribution between stromal cells, epithelial cells lining secretory glands and luminal epithelial cells during the oestrous cycle; that the steroidal regulation of the oxytocin receptor differs between endometrial cell types; and that control of the luminal epithelial oxytocin receptors is probably of particular importance to the regulation of prostaglandin F2α release at luteal regression and during the maternal recognition of pregnancy. Journal of Endocrinology (1991) 130, 199–206

Regulation of oxytocin, oestradiol and progesterone receptor concentrations in different uterine regions by oestradiol, progesterone and oxytocin in ovariectomized ewes

1996 ◽  
Vol 151 (3) ◽  
pp. 375-393 ◽  
Author(s):  
D C Wathes ◽  
G E Mann ◽  
J H Payne ◽  
P R Riley ◽  
K R Stevenson ◽  
...  
Keyword(s):  
Epithelial Cells ◽  
Low Dose ◽  
Progesterone Receptors ◽  
Cell Types ◽  
Oxytocin Receptor ◽  
Luminal Epithelium ◽  
Time Points ◽  
Progesterone Treatment ◽  
Oxytocin Receptors ◽  
Receptor Concentration

Abstract The regulation of oxytocin, oestradiol and progesterone receptors in different uterine cell types was studied in ovariectomized ewes. Animals were pretreated with a progestogen sponge for 10 days followed by 2 days of high-dose oestradiol to simulate oestrus. They then received either low-dose oestradiol (Group E), low-dose oestradiol plus progesterone (Group P) or low-dose oestradiol, progesterone and oxytocin (via osmotic minipump; Group OT). Animals (three to six per time-point) were killed following ovariectomy (Group OVX), at oestrus (Group O) or following 8, 10, 12 or 14 days of E, P or OT treatment. In a final group, oxytocin was withdrawn on day 12 and ewes were killed on day 14 (Group OTW). Oxytocin receptor concentrations and localization in the endometrium and myometrium were measured by radioreceptor assay, in situ hybridization and autoradiography with the iodinated oxytocin receptor antagonist d(CH2)5[Tyr(Me)2,Thr4,Tyr-NH29]-vasotocin. Oestradiol and progesterone receptors were localized by immunocytochemistry. Oxytocin receptors were present in the luminal epithelium and superficial glands of ovariectomized ewes. In Group O, endometrial oxytocin receptor concentrations were high (1346 ± 379 fmol [3H]oxytocin bound mg protein−1) and receptors were also located in the deep glands and caruncular stroma in a pattern resembling that found at natural oestrus. Continuing low-dose oestradiol was unable to sustain high endometrial oxytocin receptor concentrations with values decreasing significantly to 140 ± 20 fmol mg protein−1 (P<0·01), localized to the luminal epithelium and caruncular stroma but not the glands. Progesterone treatment initially abolished all oxytocin receptors with none present on days 8 or 10. They reappeared in the luminal epithelium only between days 12 and 14 to give an overall concentration of 306 ± 50 fmol mg protein−1. Oxytocin treatment caused a small increase in oxytocin receptor concentration in the luminal epithelium on days 8 and 10 (20 ± 4 in Group P and 107 ± 35 fmol mg protein−1 in Group OT, P<0·01) but the rise on day 14 was not affected (267 ± 82 in Group OT and 411 ± 120 fmol mg protein−1 in Group OTW). In contrast, oestradiol treatment was able to sustain myometrial oxytocin receptors (635 ± 277 fmol mg protein−1 in Group O and 255 ± 36 in Group E) and there was no increase over time in Groups P, OT and OTW with values of 61 ± 18, 88 ± 53 and 114 ± 76 fmol mg protein−1 respectively (combined values for days 8–14). Oestradiol receptor concentrations were high in all uterine regions in Group O. This pattern and concentration was maintained in Group E. In all progesterone-treated ewes, oestradiol receptor concentrations were lower in all regions at all time-points. The only time-related change occurred in the luminal epithelium in which oestradiol receptors were undetectable on day 8 but developed by day 10 of progesterone treatment. Progesterone receptors were present at moderate concentrations in the deep glands, caruncular stroma, deep stroma and myometrium in Group O. Oestradiol increased progesterone receptors in the luminal epithelium, superficial glands, deep stroma and myometrium. Progesterone caused the loss of its own receptor from the luminal epithelium and superficial glands and decreased its receptor concentration in the deep stroma and myometrium at all time-points. There was a time-related loss of progesterone receptors from the deep glands of progesterone-treated ewes between days 8 and 14. These results show differences in the regulation of receptors between uterine regions. In particular, loss of the negative inhibition by progesterone on the oxytocin receptor by day 14 occurred only in the luminal epithelium, but is unlikely to be a direct effect of progesterone as no progesterone receptors were present on luminal epithelial cells between days 8 and 14. The presence of oxytocin receptors in the luminal epithelium of ovariectomized ewes suggests that oestradiol is not essential for oxytocin receptor synthesis at this site. Oestradiol was able to sustain its own receptor at all sites, but high circulating progesterone was always inhibitory to oestradiol receptors. In general, oestradiol stimulated progesterone receptors in epithelial cells whereas progesterone abolished its own receptor from epithelial cells over a period of time, but had a lesser effect on stromal cells. The concentration of all three receptors is therefore differentially regulated between different uterine cell types, suggesting the importance of paracrine effects which remain to be elucidated. Journal of Endocrinology (1996) 151, 375–393

Localization of oxytocin receptor mRNA in the ovine uterus during the oestrous cycle and early pregnancy

1994 ◽  
Vol 12 (1) ◽  
pp. 93-105 ◽  
Author(s):  
K R Stevenson ◽  
P R Riley ◽  
H J Stewart ◽  
A P F Flint ◽  
D C Wathes
Keyword(s):  
Mrna Expression ◽  
Optical Density ◽  
Receptor Gene ◽  
Oxytocin Receptor ◽  
Oestrous Cycle ◽  
Luminal Epithelium ◽  
Binding Studies ◽  
Receptor Mrna ◽  
Oxytocin Receptors ◽  
Ovine Uterus

ABSTRACT A synthetic 45-mer oligonucleotide corresponding to part of the ovine endometrial oxytocin receptor cDNA was hybridized to sections of ovine uterus collected from 40 ewes at different stages during the oestrous cycle, the first 3 weeks of pregnancy and seasonal anoestrus. The quantity of oxytocin receptor mRNA was measured as the optical density (OD) value on autoradiographs using image analysis. Message first appeared in the luminal epithelium on days 14–15 of the cycle, increasing to a peak OD of 0·48 at oestrus and decreasing again between days 2 and 5. Oxytocin receptor mRNA in the superficial glands, deep glands and caruncular stroma increased between day 15 and oestrus to peak OD values of 0·17, 0·11 and 0·11 respectively, declining again by day 2 and reaching basal values (OD<0·015) by day 5. Hybridization to the myometrium tended to rise from a mean OD value of 0·01 on days 2–15 to a peak of 0·03±0·01 (mean±s.e.m.) on days 0–1, but the change was not significant. In pregnant ewes there was no detectable oxytocin receptor mRNA on days 14–15 in any region, but hybridization to the luminal epithelium was present in two of three ewes on day 21. In anoestrous ewes oxytocin receptor mRNA concentrations in all areas of the endometrium were approximately half those measured at oestrus. Optical density readings for oxytocin receptor mRNA in the various uterine compartments were compared with measurements of oxytocin receptors in the same regions as assessed by binding studies using the 125I-labelled oxytocin antagonist d(CH2)5[Tyr(Me)2,Thr4,Tyr-NH29]-vasotocin (125I-labelled OTA). In the endometrium, receptor mRNA and 125I-labelled OTA binding patterns changed in parallel, and both sets of measurements were significantly correlated (P<0·01). In the myometrium, a significant increase in 125I-labelled OTA binding occurred at oestrus; this was not accompanied by a similar increase in oxytocin receptor mRNA hybridization. This study helps to confirm that the previously identified cDNA clone is derived from the ovine oxytocin receptor, as patterns of oxytocin receptor mRNA expression in the endometrium closely resembled those of oxytocin binding. Maximum expression and binding both occurred at oestrus, suggesting that regulation of the oxytocin receptor gene in the uterus occurs principally at the transcriptional, rather than at the translational, level. Failure to detect a significant increase in myometrial mRNA expression at oestrus may indicate that the endometrial and myometrial oxytocin receptors are of different isoforms.

Blastocyst-induced ATP release from luminal epithelial cells initiates decidualization through the P2Y2 receptor in mice

2020 ◽  
Vol 13 (646) ◽  
pp. eaba3396
Author(s):  
Xiao-Wei Gu ◽  
Zi-Cong Chen ◽  
Zhen-Shan Yang ◽  
Yan Yang ◽  
Ya-Ping Yan ◽  
...  
Keyword(s):  
Epithelial Cells ◽  
Stromal Cells ◽  
Embryo Implantation ◽  
Atp Release ◽  
Sterile Inflammation ◽  
Short Exposure ◽  
Uterine Epithelial Cells ◽  
High Concentrations ◽  
Implantation Period ◽  
Luminal Epithelial Cells

Embryo implantation involves a sterile inflammatory reaction that is required for the invasion of the blastocyst into the decidua. Adenosine triphosphate (ATP) released from stressed or injured cells acts as an important signaling molecule to regulate many key physiological events, including sterile inflammation. We found that the amount of ATP in the uterine luminal fluid of mice increased during the peri-implantation period, and this depended on the presence of an embryo. We further showed that the release of ATP from receptive epithelial cells was likely stimulated by lactate released from the blastocyst through connexin hemichannels. The ATP receptor P2y2 was present on uterine epithelial cells during the preimplantation period and increased in the stromal cells during the time at which decidualization began. Pharmacological inhibition of P2y2 compromised decidualization and implantation. ATP-P2y2 signaling stimulated the phosphorylation of Stat3 in uterine luminal epithelial cells and the expression of early growth response 1 (Egr1) and prostaglandin-endoperoxide synthase 2 (Ptgs2, also known as Cox-2), all of which are required for decidualization and/or implantation, in stromal cells. Short exposure to high concentrations of ATP promoted decidualization of primary stromal cells, but longer exposures or lower ATP concentrations did not. The expression of genes encoding ATP-degrading ectonucleotidases increased in the decidua during the peri-implantation period, suggesting that they may limit the duration of the ATP signal. Together, our results indicate that the blastocyst-induced release of ATP from uterine epithelial cells during the peri-implantation period may be important for the initiation of stromal cell decidualization.

Oxytocin-stimulated phosphoinositide hydrolysis and prostaglandin F2α secretion by luminal epithelial, glandular epithelial and stromal cells from pig endometrium. II. Responses of cyclic, pregnant and pseudopregnant pigs on Days 12 and 1

2000 ◽  
Vol 12 (4) ◽  
pp. 157 ◽  
Author(s):  
Mehmet Uzumcu ◽  
Kevin G. Carnahan ◽  
Gheorghe T. Braileanu ◽  
Mark A. Mirando
Keyword(s):  
Epithelial Cells ◽  
Early Pregnancy ◽  
Stromal Cells ◽  
Prostaglandin F2α ◽  
Secretory Response ◽  
Reproductive Status ◽  
Phosphoinositide Hydrolysis ◽  
Pregnancy Recognition ◽  
Luminal Epithelial Cells

In pigs, the exact mechanism for the shift in endometrial PGF 2α secretion from an endocrine to an exocrine mode during pregnancy recognition is not known. The objective of this study was to examine whether this shift involved a change in the responsiveness of luminal epithelial, glandular epithelial and stromal cells to 0 or 100 nM oxytocin. Luminal epithelial cells, glandular epithelial cells and stromal cells were isolated from cyclic, pregnant or oestrogen-induced pseudopregnant gilts on Day 12 (Experiment 1) or Day 16 (Experiment 2) post oestrus (oestrus = Day 0). For cells obtained on Day 12, oxytocin stimulated PGF2α secretion by stromal cells (P<0.01) similarly for each reproductive status, whereas oxytocin stimulated PGF 2α secretion from luminal and glandular epithelial cells (P<0.05) from pregnant and pseudopregnant gilts but not from cyclic gilts. For both concentrations of oxytocin, mean PGF2α secretion was less (P<0.05) from stromal cells of pregnant than cyclic gilts. For cells obtained on Day 16, oxytocin stimulated PGF 2α release from stromal cells of cyclic gilts but not from stromal cells of pregnant gilts. Mean PGF 2α secretion also was less (P<0.05) from stromal cells of pregnant gilts than cyclic gilts. Oxytocin tended to stimulate PGF 2α release (P<0.07) from glandular epithelial cells of cyclic but not pregnant or pseudopregnant gilts. Luminal epithelial cells from all reproductive statuses were similarly unresponsive to oxytocin. In conclusion, the increased PGF2α secretory response to oxytocin of luminal and glandular epithelial cells from pregnant gilts on Day 12, combined with the decreased response of stromal cells from pregnant gilts on Days 12 and 16, may contribute, in part, to the shift in endometrial PGF2α secretion from an endocrine to an exocrine direction during early pregnancy in pigs.

Characterization and localization of oxytocin receptors in the uterus and oviduct of the non-pregnant ewe using an iodinated receptor antagonist

1991 ◽  
Vol 128 (2) ◽  
pp. 187-NP ◽  
Author(s):  
V. J. Ayad ◽  
S. E. F. Guldenaar ◽  
D. C. Wathes
Keyword(s):  
Binding Sites ◽  
Specific Binding ◽  
Oxytocin Receptor ◽  
Binding Characteristics ◽  
High Affinity ◽  
Oxytocin Receptors ◽  
Secretory Glands ◽  
Pregnant Ewe ◽  
Autoradiographic Technique ◽  
Specific Labelling

ABSTRACT Some of the binding characteristics of a novel oxytocin receptor ligand 125I-labelled [1-(β-mercapto-β, β-cyclopentamethylene propionic acid), 2-(ortho-methyl)-Tyr2,Thr4,Orn8,Tyr9-NH2]-vasotocin ([125I]OTA) have been determined in the sheep uterus. The compound was subsequently used for the autoradiographic localization of oxytocin receptors in the uterus and oviduct of the ewe. Specific binding of [125I]OTA to crude membrane fractions of ovine endometrium was time-dependent and was unaffected by the addition of cations to incubation media. Endometrial membranes contained a single population of saturable, high-affinity binding sites for the iodinated ligand (dissociation constant (Kd) 0·23±0·08 nmol/l) and unlabelled oxytocin competed with [125I]OTA for binding sites with high affinity (Kd 1·29±0·4 nmol/l) in the presence of Mg2+ In contrast, unlabelled OTA was able to compete with high affinity (Kd 1·13±0·16 nmol/l) in the absence of cation. Competition studies with a number of oxytocin analogues and related peptides and the tissue distribution of [125I]OTA binding sites also indicated that [125I]OTA bound to the ovine oxytocin receptor. This was further validated by autoradiographic studies which showed specific labelling with [125I]OTA to be greater to uterus and oviduct obtained from ewes which had been killed within 2 days of oestrus than to similar tissue from ewes killed during the luteal phase. In both the ampullary and isthmic regions of the oviduct and the myometrium, [125I]OTA binding sites were confined to smooth muscle. Endometrial binding sites for [125I]OTA were consistently located on the luminal epithelium and epithelial cells lining secretory glands. In addition, in one ewe which had been killed 2 days after cloprostenol treatment, stromal cells were labelled in a caruncular region of the endometrium. The consistency of this observation between similar animals remains to be determined. The autoradiographic technique demonstrated appears sufficiently sensitive to allow further studies into the distribution of the endometrial oxytocin receptor throughout the oestrous cycle, and into its regulation at luteolysis and during the establishment of pregnancy. Journal of Endocrinology (1991) 128, 187–195

scholarly journals Effect of LH on prostaglandin F2α and prostaglandin E2 secretion by cultured porcine endometrial cells

Reproduction ◽  
2005 ◽  
Vol 130 (1) ◽  
pp. 105-112 ◽  
Author(s):  
Agnieszka Blitek ◽  
Adam J Ziecik
Keyword(s):  
Epithelial Cells ◽  
Prostaglandin E2 ◽  
Stromal Cells ◽  
Prostaglandin F2α ◽  
Cell Types ◽  
Oestrous Cycle ◽  
Time Dependent ◽  
Dependent Effect ◽  
Endometrial Cells ◽  
Time Dependent Effect

LH appears to be a potent stimulator of the release of endometrial prostaglandins (PGs) in the pig. The aim of the present studies was to examine the effect of LH on PGF2αand PGE2secretion by cultured porcine endometrial cells on days 10–12 and 14–16 of the oestrous cycle and to compare its action with oxytocin. A time-dependent effect of LH (10 ng/ml) on PGF2αrelease from luminal epithelial and stromal cells on days 10–12 was observed (experiment 1). The highest increase in PGF2αsecretion in response to LH was detected in stromal cells after 6 h of incubation (P< 0.001). Epithelial cells responded to LH after a longer exposure time (P< 0.01). A concentration-dependent effect of LH (0.1–100 ng/ml) on PGF2αrelease from stromal cells was examined after 6 h and from epithelial cells after 12 h (experiment 2). Effective concentrations of LH were 10 and 100 ng/ml. LH (10 ng/ml) and oxytocin (100 nmol/l) affected PGF2αand PGE2secretion from endometrial cells on days 10–12 and 14–16 of the oestrous cycle (experiment 3). LH stimulated PGF2αsecretion from both cell types and its action was more potent on days 10–12. LH induced PGE2release, especially in epithelial cells on days 14–16. A stimulatory effect of oxytocin on PGF2αwas confirmed in stromal cells, but this hormone was also shown to enhance PGE2output. These results indicated that LH, like oxytocin, a very effective stimulator of PGF2αrelease, could play an important role in the induction of luteolysis.

Regulation of oxytocin receptor concentration in rat uterine explants by estrogen and progesterone

1983 ◽  
Vol 61 (7) ◽  
pp. 625-630 ◽  
Author(s):  
Melvyn S. Soloff ◽  
Mats Axel Fernstrom ◽  
Sumudra Periyasamy ◽  
Solweig Soloff ◽  
Sam Baldwin ◽  
...  
Keyword(s):  
Protein Synthesis ◽  
Oxytocin Receptor ◽  
Fivefold Increase ◽  
Oxytocin Receptors ◽  
Immature Rats ◽  
Receptor Concentration ◽  
17Β Estradiol ◽  
Inhibitor Of Protein Synthesis

Incubation of uterine explants from immature rats with 0.01–100 ng of 17β-estradiol/mL resulted in approximately a fivefold increase in the number of oxytocin receptors per milligram of protein in 48 h. This increase was maintained for at least an additional 48 h in the presence of estrogen. When the explants were incubated with 1 μg progesterone/mL from the outset, the concentration of oxytocin receptors was the same as initial (0 time) levels. The estrogen-induced increase in oxytocin receptor concentration was blocked by incubation with cycloheximide, an inhibitor of protein synthesis. Once increased, however, the concentration of oxytocin receptors exhibited no turnover for at least a 48-h period in the presence of estrogen. The addition of progesterone and estrogen to explants with elevated receptor levels resulted in almost a 60% reduction in oxytocin receptor concentration by 24 h, with no change in affinity of the receptor for oxytocin. The reduction in receptor concentration by progesterone was not prevented by cycloheximide. The progesterone effect may involve inactivation or degradation of oxytocin receptors or activation of substances that are inhibitory to oxytocin binding. The effects of estradiol and progesterone on oxytocin receptor concentration in uterine explants are similar to those seen when the steroids are administered in vivo. The explant system, therefore, should prove useful in clarifying factors and processes that are involved in regulation of oxytocin receptor concentration in the uterus and in the initiation of parturition in the rat.

Localization of neutral endopeptidase in the ovine uterus and conceptus during the oestrous cycle and early pregnancy

1995 ◽  
Vol 7 (1) ◽  
pp. 27 ◽  
Author(s):  
SC Riley ◽  
E Wong ◽  
JK Findlay ◽  
LA Salamonsen
Keyword(s):  
Smooth Muscle ◽  
Epithelial Cells ◽  
Smooth Muscle Cells ◽  
Early Pregnancy ◽  
Stromal Cells ◽  
Immunohistochemical Staining ◽  
Muscle Cells ◽  
Neutral Endopeptidase ◽  
Oestrous Cycle ◽  
Ovine Uterus

Neutral endopeptidase (NEP; EC 3.4.24.11), an enzyme which metabolizes several peptides (including oxytocin and endothelins) implicated in the control of uterine function, was found to be localized in the ovine uterus throughout the oestrous cycle and in the uterus and conceptus during early pregnancy, using immunohistochemical techniques. Positive NEP immunoreactivity was found in the endometrium principally in stromal cells, in the vasculature in endothelial and vascular smooth muscle cells, and also weakly in some glandular epithelial cells. In a layer of stromal fibroblasts several cells in thickness underlying the luminal epithelium, staining was much weaker than that in the deeper stromal cells throughout the period examined. NEP staining was also present in smooth muscle cells of the myometrium at all times, and was most intense in the layer of cells adjacent to the endometrium. In the conceptus, NEP immunohistochemical staining was found in uninucleate cells, but not in binucleate trophoblast cells, in epithelial cells of the allantois and amnion, and in the heart and brain of the Day-20 embryo. In ovariectomized ewes treated with oestrogen or progesterone separately or remaining untreated, immunohistochemical staining of NEP was stronger when compared with intact ewes, in caruncular and intercaruncular stroma and epithelia, in glands, in the vasculature and in myometrium. The staining was less intense in all cell types in ewes receiving oestrogen plus progesterone. The expression of NEP and its specific regionalization within the uterus indicate a mechanism by which the availability of biologically important peptides involved in the regulation of the oestrous cycle and implantation, including oxytocin and endothelin, can be controlled by regulation of their metabolism.

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