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Query: UNIPROT:P01178 (oxytocin)
 15,767 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The spontaneous contractility of the epididymis in the rat was recorded in vivo and the effects of the neurohypophyseal hormones were studied. Oxytocin (50 muU and 500 muU/100 g body weight) produced a progressive increase in tonus together with an increase in amplitude and frequency of the contractions. Vasopressin (100 muU and 1000 muU/100 g body weight) showed similar effects. No differences were apparent at the doses studied.
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PMID:The 'in vivo' effects of oxytocin and vasopressin on spontaneous contractility of the rat epididymis. 1 18

The effects of norepinephrine, phentalamine, oxytocin, vasopressin, several prostaglandins, and indomethacin on the spontaneous motility of isolated guinea pig cauda epididymidis were explored. Phentolamine and indomethacin reduced the isometric peak tension of spontaneous epididymal contractions. Phentolamine also depressed the frequency. Both findings suggest that catecholamines and endogenous prostaglandins are in some way regulators of the spontaneous motility of the cauda epididymidis. Norepinephrine resulted in the development of a distinct, sustained, tonic contraction without phasic activity, whereas prostaglandins E1, E2, and F2 alpha elicited a tonic increase accompanied by frequent, superimposed, phasic contractions. Both oxytocin and vasopressin comparably enhanced epididymal motility, producing contractile responses similar to those observed with prostaglandins. Since the epididymal contractions can influence the time spent by spermatozoa in passing through the ductus epididymidis, the above-mentioned compounds could play an important role in spermatozoal transport via modulation of epididymal contractile activity. In addition, such naturally occurring substances might regulate the release of sperm from the last portion of the epididymis into the ductus deferens.
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PMID:Physiologic and pharmacologic studies on the motility of isolated guinea pig cauda epididymidis. 80 41

The presence, possible biosynthesis, and uptake of oxytocin from luminal fluid in the ductuli efferentes and caput epididymidis of the ram were studied. Specific immunostaining for oxytocin, but not neurophysin, was observed in the ductuli efferentes as well as caput epididymidis. This indicates the presence, but not production, of oxytocin in epithelial cells of these ducts. Staining was predominantly present in the epithelium, especially in the middle lobules of the ductuli efferentes and initial segment of the epididymis. Endocytosis of oxytocin was studied by electron microscopy after intraluminal microinjections of oxytocin conjugated to colloidal gold (8-10 nm), a 20-fold excess of oxytocin followed by oxytocin-gold, or plain colloidal gold into the ductuli efferentes and four successive regions of the caput epididymidis. Specific uptake by a receptor-mediated process was evidenced by the presence of more gold particles within epithelial cells after oxytocin-gold injections than after control injections. The quantity of oxytocin-gold endocytosed was 3.7-fold greater in the ductuli efferentes than in the initial segment of the epididymis. Within the caput epididymidis, more oxytocin-gold was endocytosed in the initial segment and proximal caput epididymidis than in two distal regions. We conclude that localization of oxytocin in epithelia of the excurrent ducts is a consequence of endocytosis (predominantly receptor mediated) of luminal oxytocin entering in rete testis fluid; however, uptake of blood-borne oxytocin cannot be excluded. Although oxytocin may have a role in sperm transport via action on smooth muscle in the ductal wall, the regional pattern of endocytosis of oxytocin is suggestive of a role for oxytocin in epithelial function in the ductuli efferentes and proximal portions of the caput epididymidis.
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PMID:Oxytocin in the ovine ductuli efferentes and caput epididymidis: immunolocalization and endocytosis from the luminal fluid. 229 56

Neurohypophysial hormones stimulate the motility of tunica albuginea, epididymis, and vas deferens acting through oxytocin (OT) and V1 vasopressin receptors. To test the hypothesis that these hormones are involved also in the regulation of seminal vesicle physiology, we studied binding of [3H]OT and [3H] arginine vasopressin ([3H]AVP) to porcine seminal vesicle membranes. Neurohypophysial hormones bind to two different classes of sites. The first class shows low capacity (35 fmol per mg of protein) and a very high affinity (Kd less than 1 nM) for both the labeled ligands. The second class is characterized by a high capacity (2000 fmol per mg of protein) and a high affinity for AVP (Kd approximately equal to 2.5 nM), whereas OT has 160 times lower affinity. Lysine vasopressin and the V1 antagonist [1-deaminopenicillamine, 2-(O-methyl)tyrosine]Arg8-vasopressin compete with high affinity with [3H]AVP binding, whereas the V2 agonist [1-deamino,4-valine]D-Arg8-vasopressin (dVDAVP) is 110 times less potent than AVP. The OT agonist [Thr4,Gly7]OT and the OT antagonist [1(beta-mercapto-beta, beta-cyclopentamethylene propionic acid), 2-(O-ethyl)tyrosine, 8-ornithine]vasotocin failed to affect [3H]AVP binding. These findings seem to suggest that AVP interacts with the V1 vasopressin isoreceptor in porcine seminal vesicle membranes. However, AVP stimulates adenylate cyclase activity in a dose-dependent fashion with an EC50 of 14 nM, whereas OT or dVDAVP has no effect at 100 nM. Moreover, a well-characterized V1 vasopressin antagonist, [1-(beta-mercapto-beta, beta-cyclopentamethylene propionic acid),2-(O-methyl)tyrosine]Arg8-vasopressin [d(CH2)5Tyr(Me)AVP], competes with [3H]AVP binding with an IC50 of 0.17 microM. These pharmacological properties are distinct from the previously described V1 and V2 vasopressin receptors and indicate the presence of a new class of AVP receptors. Although this vasopressin isoreceptor shares some pharmacological characteristics with the V1 (pressor) isoreceptor, it has low affinity for the V1 antagonist d(CH2)5-Tyr(Me)AVP and is linked to the adenylate cyclase system. The extremely high density of AVP receptors in porcine seminal vesicles (2 pmol per mg of protein) is comparable to the density of V2 vasopressin receptors in porcine renal medulla, suggesting a physiological role for vasopressin in the seminal vesicle.
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PMID:Identification and characterization of a vasopressin isoreceptor in porcine seminal vesicles. 294 37

The neurohypophysial hormones oxytocin (OT) and vasopressin (VP) are involved in the regulation of the contractility of the male genital tract in several animal species. We investigated the presence of specific binding sites for [3H]OT and [3H]arginine VP (AVP) in membranes prepared from tunica albuginea, epididymis, and vas deferens from prepubertal pigs 2-16 weeks of age. Membranes were incubated with [3H]OT and [3H]AVP in the presence or absence of the corresponding unlabeled peptides. Binding equilibrium was reached in 60 min at 22 C. Millimolar concentrations of Mg2+ increased the specific binding of both ligands. Analysis of families of self- and cross-displacement curves using the computer program LIGAND clearly demonstrated that two classes of binding sites were present in all tissues investigated. The first class of sites, designated the OT site, shows high affinity for OT, AVP, lysine vasopressin, arginine vasotocin, the selective OT agonists [Thr4,Gly7]OT and [Asu1,6]OT, and the OT antagonists derived from ornithine vasotocin (OVT), namely d(CH2)5Tyr(Et)OVT and dEt2OVT. The second class of sites, designated the VP site, shows high affinity for AVP, lysine vasopressin, arginine vasotocin, and the selective V1 antagonist d(CH2)5Tyr(Me)AVP. The V2 agonist [1-deamino,4-valine]8-D-AVP shows low affinity for both sites. Isotocin, desglycinamide [Arg-8]AVP and tocinoic acid were ineffective in displacing [3H]AVP or [3H]OT. The highest density of OT receptors was found in tunica albuginea and epididymis, whereas the highest density of AVP receptors was found in vas deferens. Adenylate cyclase was not activated in any of the tissues studied by concentrations of AVP or OT up to 100-fold greater than their Kd values. This is the first demonstration and pharmacological characterization of specific OT and V1 VP receptors in the tunica albuginea, epididymis, and vas deferens. The recent demonstration of high local concentration of neurohypophysial hormones in the gonads of several mammals support a physiological role of these OT and VP receptors in regulation of the motility of the male genital tract.
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PMID:Identification and characterization of two classes of receptors for oxytocin and vasopressin in porcine tunica albuginea, epididymis, and vas deferens. 302 94

The testes of several species contain oxytocin and/or neurophysin, but the content or localization of oxytocin in epididymal tissue has not been studied. The present study was undertaken to localize oxytocin and neurophysin in epididymal tissue of the ram, and to quantify oxytocin in the ductus epididymidis and fluids entering and leaving the ductus epididymidis. Neurophysin was not detected in the epididymis; thus, synthesis of oxytocin by the epididymis is unlikely. Immunohistochemical localization of oxytocin was confined to the epithelium and capillaries. Oxytocin immunostaining was most intense for epithelium of the caput and declined in corpus and cauda regions. However, based on radioimmunoassay, no difference in oxytocin concentration was detected among regions of the epididymis. Since rete testis fluid entering and cauda epididymal fluid leaving the epididymis contained at least fourfold more oxytocin than testicular venous plasma, it was concluded that regional differences in epithelial concentration of oxytocin may have been masked by oxytocin contained in the luminal fluid. It was concluded further that the epididymis of the ram does not synthesize oxytocin, but about 22 ng/day enters the epididymis in rete testis fluid. Most of this luminal oxytocin apparently is absorbed by the epithelium of the caput epididymidis, with additional adsorption in the corpus and cauda. Although a role for oxytocin in ductal contractility cannot be excluded, it is more likely that the luminal oxytocin influences epithelial or sperm function.
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PMID:Evidence for the presence of oxytocin in the ovine epididymis. 317 87

The mammalian testes have several mechanisms to propel the nonmotile spermatozoa in the seminiferous tubules through the rete testis into the epididymis. These include (a) contractions of the testicular capsule and the seminiferous tubules and (b) fluid flow through the excurrent ducts resulting from active transport of fluids and electrolyte into the seminiferous tubules from the extracellular space. The efflux of fluids and sperm from the testis appears to closely parallel spermiation. An increased output of fluid may result from prostaglandins (PGF2 alpha) and possibly oxytocin (not all species respond to oxytocin) as a result of capsular contractions compressing and expelling the fluid from the tubules. Seminiferous tubular contractions do not result from nervous stimulation but are linked to PGs and cyclic nucleotide generation. They are regulated to some extent by androgens and the lesser response of the tubules to 5 alpha-dihydrotestosterone compared to testosterone can be explained by their interaction with androgen binding protein and their action on phospholipase A2 activity for PG synthesis.
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PMID:Contractility of seminiferous tubules as related to sperm transport in the male. 611 19

Oxytocin is present in the mammalian testis where it increases contractility of seminiferous tubules in vitro and has been implicated in sperm transport. The present study investigated whether oxytocin affects the transport of spermatozoa from the testis in vivo. In rats, mature spermatozoa are first seen in the testis 42 days postpartum and arrive in the epididymis at about day 45. Male Wistar rats were given daily subcutaneous injections of either oxytocin (0.5 micrograms), the oxytocin antagonist des Gly-NH2d(CH2)5-[D-Tyr2,Thr4]OVT (0.2 micrograms) or saline from day 40 postpartum. Groups of six animals were killed 2 h after their last injection on days 43, 44, 45 and 46 postpartum. Testes were removed and fixed in Bouin's fluid for histological examination and the number of spermatozoa in the epididymides was counted. Spermatozoa were seen in the epididymis earlier in the oxytocin-treated rats (day 43) than in the control animals (day 44), and treatment with the antagonist delayed the appearance of spermatozoa in the epididymis until day 45. When the testes were examined, residual bodies, which were used as an indicator of spermiation, were seen only in one control animal before day 44. Residual bodies were seen in the testes of all oxytocin-treated rats on day 43 but were not detected until day 45 in the oxytocin antagonist-treated rats. These data show that in rats oxytocin can affect the arrival of spermatozoa in the epididymis. Although this may be due in part to effects on tubal transport or the secretion of tubular fluid, these findings suggest that the peptide may affect spermiation.
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PMID:Effects of oxytocin on sperm transport in the pubertal rat. 888 97

Oxytocin is localized to the Leydig cells of the testis in the rat and several other species where it is postulated to play a role in steroidogenesis and seminiferous tubule contractility. Oxytocin has also been detected in the epididymis of the ram where active uptake of the peptide from luminal fluid has been demonstrated. This study was performed to investigate whether oxytocin is present in the rat epididymis, and the origin of the peptide. Immunoactive oxytocin was detected in the epididymis of all control animals examined (147.7 +/- 41.7 pg/g). Total epididymal oxytocin was reduced significantly following castration (p < 0.05). Testosterone treatment also reduced the epididymal concentration of the peptide in both intact and castrated rats. Efferent duct ligation (EDL) did not affect the presence of oxytocin in the epididymis. Immunoactive oxytocin was localized in discrete cells of the epithelium of the caput epididymis, with less staining apparent in the initial segment and cauda epididymis. Staining disappeared from the caput epididymis following castration, but reappeared following testosterone supplementation. No obvious alteration in staining was observed in the cauda epididymis after EDL. These data demonstrate for the first time the presence of oxytocin in the epididymis of the rat and that the peptide may be regulated by androgens. They further suggest an epididymal source of the peptide.
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PMID:Epididymal oxytocin in the rat: its origin and regulation. 898 76

Using a combination of reverse transcriptase polymerase chain reaction to detect specific mRNA and immunohistochemistry employing antibodies that recognize two different epitopes for each molecule, the local production of oxytocin (OT) and its cognate receptor was investigated in the male marmoset monkey (Callithrix jacchus). There was synthesis of both OT and the oxytocin receptor (OTR) within the testis, and both were markedly expressed within the Leydig cells. A weak staining for both OT and its associated neurophysin could also be detected in Sertoli cells in some animals. Expression of OT or neurophysin does not appear to be significant in the epididymis, though there appears to be synthesis of the receptor in some peritubular muscle cells of the epididymis and in the vas deferens. Within the prostate, there appears to be no production of OT or neurophysin, though there appears to be weak expression of the OTR in the basal layers of the secretory epithelium. Similarly in the bulbourethral gland, only OTR immunoreactivity could be detected. Receptors appear to be present in the myoid cells encompassing the glandular lobules and are presumably able to respond to systemic OT. An analysis of juvenile marmosets indicates that the testicular OT system appears to become established during puberty. Thus, in this New World monkey the testis is able to support a local OT-based paracrine-type system, though the prostate and bulbourethral gland are probably only able to respond to exogenous OT.
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PMID:Oxytocin and oxytocin receptor expression in reproductive tissues of the male marmoset monkey. 911 41


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