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

Transitional epithelium lining rabbit urinary bladders was isolated and studied in vitro. The homogeneity of the isolated epithelium was demonstrated by light and electron microscopical monitoring as well as cell culture studies. Transitional epithelium responded to epinephrine and prostaglandin E1 (PGE1) in the presence of 2mM 1-methyl, 3-isobutylxanthine (MIX) with increases in intracellular levels of cyclic adenosine 3':5'-monophosphate (cyclic AMP). Corticotropin, aldosterone, insulin, parathyroid hormone and vasopressin were slightly but significantly stimulatory under similar conditions. Glucagon and oxytocin were not stimulatory at the concentrations tested. The effects of epinephrine and PGE1 were potentiated by 2mM MIX 20-fold or greater. The cells were slightly more sensitive to PGE1 then to epinephrine. The prostaglandin produced a noticeable response at about 10nM, while effects of epinephrine were discernible at 0.1muM. Maximal responses to both effectors were seen at about 10muM. The action of 10muM epinephrine, but not 10muM PGE1, was completely abolished by 0.1mM propranolol. Responses to combinations of epinephrine and PGE1 were additive. Cyclic AMP accumulated in the incubation medium of transitional epithelial cells exposed to epinephrine, PGE1, MIX, or combinations of the agonists. The appearance of cyclic AMP in the medium was slow compared to the rate of intracellular accumulation, but reached significant levels following prolonged stimulation.
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PMID:The effects of hormones on cyclic adenosine 3':5'-monophosphate accumulation in transitional epithelium of the urinary bladder. 17 60

The distribution of vasopressin (VP), oxytocin (OXY) and neurophysins 1 and 2 (N1, N2) has been studied in the median eminence (ME) of normal, heterozygous (HDI) and Brattleboro (DI) rats. Numerous thin periportal VP and N2 fibres exist in the normal and HD1 rats; they have never been observed in the DI rats. N1 and OXY fibres in the external layer of the median eminence are rare. Adrenalectomy increases periportal VP and N2 loading in normal and HDI rats; it does not modify the appearance of the DI median eminence. Dexamethasone prevents external VP and N2 overloading in adrenalectomized rats injected during the whole postoperative period. Injections of vasopressin indicated that it had a negative feedback effect during a short time (3 days) but not during a longer period (7 days). The suprachiasmatic neurons are stained only by anti-VP and anti-N2 antibodies. Their overstaining induced by adrenalectomy disappears with dexamethasone, aldosterone or vasopressin treatment. This central effect of hormones is not necessarily associated with disappearance of overloading in the external layer of the ME. The hypothalamo-infundibular tract carrying VP and N2 is involved in regulatory mechanisms of the corticotrope axis. Its relationships with suprachiasmatic neurons are discussed.
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PMID:Infundibular localization of vasopressin, oxytocin and neurophysins in the rat; its relationships with corticotrope function. 22 Oct 71

The responses of isolated frog skin to 5-hydroxytryptamine (increased active sodium transport and decreased passive chloride permeability) are diminished by incubation with the enzymes neuraminidase and N-acetylneuraminic acid aldolase but only in the absence of Ca2+ and presence of EDTA. The responses induced by oxytocin, adrenalin and aldosterone are unaffected by enzyme treatment.
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PMID:Selective destruction of 5-hydroxytryptamine receptors by neuraminidase. 31 8

The effect of the treatment was controlled by measurements of plasma renin activity and aldosterone concentration. These observations concern maternal toxemia treated by diuretic and dietary sodium restriction two weeks before delivery. In two cases, labor was augmented with oxytocin infusion. These cases illustrate the respective role of sodium depletion and hemodilution in the occurrence of maternal and neonatal hyponatremia. They emphasize the amount of sodium supplementation in these newborn infants.
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PMID:[Neonatal hyponatremia from maternal origin. Three cases (author's transl)]. 40 18

In a previous report we demonstrated the presence of a vasotocin (AVT)-like peptide in chromaffin cells of the amphibian adrenal gland and showed that synthetic AVT is a potent stimulator of corticosterone and aldosterone secretion by frog adrenocortical cells. In the present study we evaluated the relative potency of various AVT analogs and investigated the mechanism of action of AVT on frog interrenal (adrenal) tissue. Several AVT agonists, including hydrin 2, oxytocin (OXT), arginine vasopressin (AVP), Lys-conopressin G, and mesotocin (MT), were able to mimic the stimulatory effect of AVT on steroid secretion, but AVT was by far the most potent stimulator of steroidogenesis. In the series of analogs studied, the order of potency was: AVT greater than hydrin 2 greater than OXT greater than AVP greater than Lys-conopressin G greater than MT greater than [deamino-Cys1,D-Arg8]AVP greater than [d(CH2)5,Tyr(OMe)2] AVP. The effect of AVT (5 x 10(-10) M) was totally blocked by both the antidiuretic V2 antagonist [d(CH2)5,D-Phe2,Ile4,Ala9-NH2]AVP (10(-6) M) and the oxytocinergic antagonist [d(CH2)5,Tyr(OMe)2,Orn8]AVT (10(-6) M); the V2 antagonist was approximately twice as potent as the OXT antagonist. In contrast, the V1 antagonist 1-(1-mercapto-4-phenylcyclohexaneacetic acid)-AVP (10(-6) M) did not affect the response of the interrenal tissue to AVT. Indomethacin (5 microM), a cyclooxygenase inhibitor, induced a dramatic decrease in the spontaneous secretion of corticosteroids, but did not impair the stimulatory effect of AVT (5 x 10(-9) M) on corticosterone and aldosterone secretion. In addition, AVT did not stimulate the production of prostaglandin E2, suggesting that prostaglandins are not involved in the mechanism of action of AVT. Concurrently, AVT did not modify cAMP production by frog adrenal slices. In contrast, AVT induced both an increase in inositolphosphate production and a reduction of membrane phospholipid content. We conclude that in the frog adrenal gland, the stimulatory effect of AVT on steroid secretion is mediated through activation of receptors related to the mammalian V2 and/or OXT receptors, which are positively coupled to phosphoinositide-specific phospholipase C.
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PMID:Pharmacological characterization of vasotocin stimulation of phosphoinositide turnover in frog adrenal gland. 130 45

The effect of aldosterone (1 mumol/l for 4-6 h) on Na+ transport across toad skin (Bufo viridis) was studied in skins preincubated in vitro. Short-circuit current (Isc) was consistently and reproducibly elevated in skins from NaCl(100 and 200 mmol/l)-acclimated toads, where the baseline Isc was greatly reduced. The effect of aldosterone was tested in NaCl and NaNO3 Ringer's and also after oxytocin (50 mU/ml) in the latter conditions. Apical membrane conductance of the principal cells increased consistently after aldosterone in all skins and was linearly correlated with the Isc under all conditions. This confirms that the stimulation of Na+ transport originates from the effect of the aldosterone on apical Na+ channels. Basolateral membrane conductance was also significantly elevated compared with control pieces in those tissues that were preincubated with aldosterone for 4-6 h. The increase, however, did not correlate with the magnitude of the Isc. It is therefore concluded that aldosterone specifically stimulates, in addition to the apical effect, the basolateral membrane conductance. This stimulation appears to be direct and not a secondary response to the elevation of transepithelial transport rate.
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PMID:The effect of aldosterone on sodium transport and membrane conductances in toad skin (Bufo viridis). 165 21

The effects of the activation of protein kinase A (PKA), protein kinase C (PKC) and corticosteroids were investigated on the release of corticotrophin-releasing factor-41 (CRF), arginine vasopressin (AVP) and oxytocin from rat fetal hypothalamic cells in culture. Both forskolin and PMA (phorbol 12-myristate 13-acetate) increased CRF, AVP and oxytocin release, while dexamethasone and aldosterone only reduced basal secretion of CRF. Both steroids also inhibited forskolin-induced CRF, AVP and oxytocin responses to PMA. These data provide direct evidence for a role for both PKC- and PKA-mediated mechanisms in the regulation of CRF, AVP and oxytocin release and for differential effects of both glucocorticoids and mineralocorticoids on PKA- and PKC-stimulated responses.
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PMID:Release of corticotrophin-releasing factor-41, arginine vasopressin and oxytocin from rat fetal hypothalamic cells in culture: response to activation of intracellular second messengers and to corticosteroids. 173 59

Oxytocin (OT) is known to stimulate natriuresis in rats when administered in large doses that produce high plasma levels. We examined the effects of physiological plasma OT levels on renal sodium excretion by infusing graded doses of OT sc in conscious adult male rats maintained on a sodium-deficient diet. Our results demonstrate that OT causes a dose-related increase in urinary sodium excretion during the initial day of infusion. The lowest plasma OT levels associated with increases in urinary sodium excretion (5-6 pmol/liter) were well within the range of physiological OT secretion in rats. However, this natriuretic effect was not sustained during subsequent days of maintenance on a sodium-deficient diet, suggesting that the OT-induced natriuresis was limited in part by receptor desensitization and/or a decreased exchangeable sodium pool in combination with secretion of opposing antinatriuretic factors such as aldosterone. Pretreatment with an OT receptor antagonist completely blocked the natriuresis produced by a 20 pmol/h infusion of OT, but urinary sodium excretion was not affected by a vasopressin V1 antagonist and was blocked only partially by a combined vasopressin V1 and V2 antagonist. Together with previous studies in rats demonstrating an inverse relation between pituitary OT secretion and sodium appetite, these results support the hypothesis that peripherally and centrally secreted OT act in concert in rats to produce a negative sodium balance by stimulating sodium excretion while inhibiting sodium ingestion.
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PMID:Oxytocin produces natriuresis in rats at physiological plasma concentrations. 184 54

The influence of arginine vasotocin (AVT) on the interrenal secretion of the clawed toad (Xenopus laevis) was studied combining in vivo and in vitro experiments. In vivo: A single injection of 3 nmol AVT per 100 g body weight was given, and the concentrations of corticosterone and aldosterone in the serum were measured after 1, 3, 6, 12, and 24 hr. The serum levels of both steroids remained elevated over 6 hr and declined to normal levels within 12 hr. The increase of the aldosterone concentration was relatively stronger than that of corticosterone. In vitro: A perifusion system was used to study the influence of AVT concentrations ranging from 0.1 to 50 nM on the secretion rates of corticosterone and aldosterone. The response of the interrenals was dose dependent; corresponding to the in vivo results, the elevation rate was higher for aldosterone than for corticosterone. The effects of several nonapeptides were compared. AVT was most effective, followed by mesotocin and arginine vasopressin (AVP). Isotocin and oxytocin had less effect. The selective agonist of the mammalian V2 receptor (1-deamino-8-D-arginine)-vasopressin (DDAVP) did not stimulate the interrenals, while the V1 receptor-selective antagonist ((1-beta-mercapto-beta,beta-cyclopentamethylene propionic acid)-2-(O-methyl)-tyrosine)-AVP could not diminish the stimulation by AVT. Thus, the AVT receptor of the amphibian interrenal must be a special one and is different from the V1 and V2 types of mammals. In a comparison of the effects of AVT with other stimulators such as ACTH(1-28) or urotensin II, it was found that the sensitivity of the interrenals to AVT was similar to that of these peptides. The results indicate that AVT plays an important role in the osmomineral regulation of Xenopus laevis by acting on the corticosteroid secretion of the interrenals.
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PMID:Neurohypophysial hormones and steroidogenesis in the interrenals of Xenopus laevis. 196 9

The presence of neurohypophyseal nonapeptides in the adrenal gland of nonmammalian vertebrates and the possible action of these regulatory peptides on corticosteroid secretion have never been investigated. We have applied the indirect immunofluorescence technique to examine whether vasotocin (AVT) and/or mesotocin (MT) are located in frog adrenal (interrenal) tissue. Using antisera against AVT and tyrosine hydroxylase, we found that all chromaffin cells contain an AVT-like peptide. Labeling of consecutive sections with phenylethanolamine-N-methyltransferase or AVT antibodies showed that both noradrenaline- and adrenaline-storing cells contain AVT-like immunoreactivity. In contrast no labeling of frog adrenal slices was observed using a MT antiserum. At the ultrastructural level, the immunogold technique revealed that the AVT-immunoreactive peptide is sequestered in chromaffin granules with varying electron densities. Filtration of frog adrenal tissue extracts on Sep-Pak C-18 cartridges showed that the elution profile of the AVT-like peptide was similar to that of synthetic AVT. The apparent concentration of AVT in the adrenal was 2.7 ng/g tissue. Since chromaffin cells represent approximately one third of all interrenal cells, the actual concentration of AVT in chromaffin tissue was about 8 ng/g tissue. The role of AVT in the regulation of frog adrenal steroidogenesis was studied in vitro using perifused frog interrenal slices. Graded doses of AVT (10(-10)-10(-7) M) induced a dose-dependent stimulation of both corticosterone and aldosterone secretion. The other neurohypophyseal peptides (vasopressin, oxytocin, and MT) were also able to enhance corticosteroid secretion, but AVT was by far the most potent stimulator of steroidogenesis. Prolonged administration (4 h) of AVT induced a rapid increase in corticosterone and aldosterone output, followed by a gradual decline of corticosteroid secretion. These results show that an AVT-like peptide is stored in chromaffin granules of frog adrenal gland. Our data also indicate that synthetic AVT is a potent stimulator of corticosteroid secretion by frog interrenal cells. Since in amphibians adrenocortical and chromaffin cells are intimately intermingled, these results suggest that AVT produced by chromaffin cells may regulate corticosteroid release locally, through a cell to cell mode of communication.
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PMID:Identification of vasotocin-like immunoreactivity in chromaffin cells of the frog adrenal gland: effect of vasotocin on corticosteroid secretion. 267 89


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