Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P01178 (oxytocin)
 15,767 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Oxytocin, bradykinin, melittin and A23187 increased cyclic GMP levels through activation of soluble guanylate cyclase in cultured porcine kidney epithelial cells, LLC-PK1. NG-monomethyl-L-arginine, an inhibitor of endothelium-derived relaxing factor/nitric oxide formation, decreased both basal and stimulated levels of cyclic GMP in a concentration-dependent manner. L-Arginine, but not D-arginine, augmented basal as well as stimulated levels of cyclic GMP and prevented the inhibition induced by NG-monomethyl-L-arginine. Similar effects of L-arginine were also observed with L-argininamide, L-arginine ethyl ester, L-arginine methyl ester and the dipeptide L-arginyl-L-aspartic acid. NG-monomethyl-L-arginine did not affect cyclic GMP accumulation induced by sodium nitroprusside, an activator of soluble guanylate cyclase, and atrial natriuretic factor, an activator of particulate guanylate cyclase. Stimulatory effects of oxytocin, glyceryl trinitrate, sodium nitroprusside, bradykinin, melittin and A23187 on cyclic GMP accumulation were enhanced with superoxide dismutase and diminished with oxyhemoglobin. However, atrial natriuretic factor-induced cyclic GMP accumulation was not affected. Furthermore, endothelium derived relaxing factor-like activity was detected in the conditioned medium from LLC-PK1 cells stimulated with oxytocin. Based on these data, we conclude that endothelium-derived relaxing factor is produced in this cell type and participates in the regulatory mechanism of cyclic GMP formation as an intra- and intercellular messenger for activation of soluble guanylate cyclase.
 ...
PMID:Formation of endothelium-derived relaxing factor in porcine kidney epithelial LLC-PK1 cells: an intra- and intercellular messenger for activation of soluble guanylate cyclase. 167 Oct 98

Oxytocin increased cyclic GMP levels in LLC-PK1 porcine kidney epithelial cells through activation of soluble guanylate cyclase. NG-Monomethyl-L-arginine and N omega-nitro-L-arginine inhibited oxytocin (10 microM) induced cyclic GMP accumulation with IC50 values of 2.3 microM and 140 nM, respectively, and the inhibition was prevented with L-arginine. Both inhibitors at 100 microM lowered the basal levels of cyclic GMP, but did not affect those induced by 1 microM sodium nitroprusside and 100 nM atrial natriuretic factor. These data support our hypothesis that an endothelium-derived relaxing factor-like substance is formed as the endogenous activator of soluble guanylate cyclase in an L-arginine-dependent fashion in various cell types. N omega-Nitro-L-arginine is 16 times more potent than NG-monomethyl-L-arginine as a specific inhibitor of this pathway in LLC-PK1 cells.
 ...
PMID:N omega-nitro-L-arginine: a potent inhibitor of the L-arginine-dependent soluble guanylate cyclase activation pathway in LLC-PK1 cells. 197 29

Recently, it was shown that in LLC-PK1 kidney epithelial cells hormones such as vasopressin or oxytocin increase cyclic GMP in a receptor-mediated and L-arginine-dependent manner. In the present study, the possible existence of cross-tolerance to vasopressin and oxytocin was investigated in nitrate-tolerant LLC-PK1 cells. Pretreatment with 1 mM glyceryl trinitrate for 3 h decreased cyclic GMP stimulation by 1 microM vasopressin and 1 microM oxytocin by 49% and 54%, respectively. Under the same conditions, cyclic GMP stimulation at 1 microM sodium nitroprusside was diminished by 56% whereas the cyclic GMP response to 100 microM glyceryl trinitrate was virtually abolished. Our results demonstrate that a substantial degree of cross-tolerance to L-arginine-dependent guanylate cyclase activators occurs in nitrate-pretreated nonvascular cells which may be due to glyceryl trinitrate-induced desensitization of soluble guanylate cyclase.
 ...
PMID:Cross-tolerance to L-arginine-dependent guanylate cyclase activators in nitrate-tolerant LLC-PK1 kidney epithelial cells. 197 70

Recently, it has been reported that oxytocin (OT) produces diuresis by its interaction with OT receptors in the kidney. LLC-PK1 cells have been used as a model system for renal epithelial cells. To determine if OT stimulates receptor-mediated phosphoinositide (PI) hydrolysis in LLC-PK1 cells as it does in nonrenal cell systems, we measured the release of PI hydrolysis products in LLC-PK1 cells by OT and a selective OT agonist (AK-2-60) in the absence and presence of a selective OT antagonist (KB-5-21). In addition, we determined the effect of an increase in osmolality of the incubation medium on OT-stimulated PI hydrolysis in LLC-PK1 cells. The methods involved the incubation of LLC-PK1 cells with [3H]inositol for its incorporation into membrane PI and the measurement of the release of [3H]inositol phosphates in the presence of LiCl which prevents dephosphorylation. The osmolality of the incubation media was increased from 300 mOsmol/kg of H2O to 600, 900 and 1200 mOsmol/kg of H2O by addition of NaCl and urea. In an iso-osmotic incubation medium OT (10(-11) M) produced a greater than 100% increase in PI hydrolysis in LLC-PK1 cells. The OT agonist, AK-2-60, produced a significant increase in PI hydrolysis in LLC-PK1 cells at 10(-8) M concentration. The effects of both OT and its agonist were concentration-dependent and were blocked by the OT antagonist, KB-5-21. An increase in osmolality of the incubation media decreased OT-stimulated PI hydrolysis in LLC-PK1 and abolished completely the effect of OT at 1200 mOsmol/kg of H2O.(ABSTRACT TRUNCATED AT 250 WORDS)
 ...
PMID:Stimulation of phosphoinositide hydrolysis by oxytocin in renal epithelial cells. 215 51

Two selective radioligands for oxytocin receptors, [3H]-[4-threonine,7-glycine]oxytocin [( 3H]-[Thr4,Gly7]OT) and 125I-[1-(beta-mercapto-beta,beta-cyclopentamethylenepropionic acid), 2-(O-methyl)tyrosine, 4-threonine, 8-ornithine, 9-tyrosine amide]-oxytocin (125I-OTA), were used to characterize oxytocin receptors from two pig kidney-derived cell lines, LLC-PK1 and LLC-PK1L. [3H]-[Thr4,Gly7]OT and 125I-OTA bind with high affinity (mean Kd values of 14 and 0.06 nM, respectively) to the same population of sites on LLC-PK1 cell membranes [maximum binding (Bmax) of 100 fmol/mg membrane protein]. These sites had the expected ligand selectivity of oxytocin receptors. [3H]-[Thr4,Gly7]OT and 125I-OTA binding sites could be distinguished from V2 vasopressin receptors present on LLC-PK1 and LLC-PK1L cells on the basis of clearly different maximal capacities and ligand selectivities, different sensitivities to insulin and serum, and absence of heterologous downregulation. Oxytocin receptors from LLC-PK1 cells have no functional relationship with adenylate cyclase. [Thr4,Gly7]OT affected neither the basal adenosine 3',5'-cyclic monophosphate (cAMP) content nor the vasopressin-induced cAMP accumulation by LLC-PK1 cells. Xenopus laevis oocytes injected with LLC-PK1 cell mRNA responded to [Thr4,Gly7]OT by an increase in 45Ca2+ outflux; this effect is antagonized by a highly selective oxytocin antagonist.
 ...
PMID:Oxytocin receptors from LLC-PK1 cells: expression in Xenopus oocytes. 215 46

Arginine vasopressin (AVP) is a potent neuroactive and vasoactive nonapeptide encoded in and processed from a precursor, preproarginine vasopressin-neuro-physin II (preproAVP-NPII). To study the physiologic consequences of a genetic model of chronic hypervasopressinemia transgenic mice were produced by introduction of a mouse metallothionein-rat-ppAVP-NPII fusion gene into the germ line of mice. Three stable transgenic pedigrees were analyzed through several generations. Levels of immunoreactive AVP and neurophysin (NP) in sera, livers, kidneys, intestines, pancreas, and brains were markedly elevated. Chromatographic analyses showed sera levels of approximately 500 pg/ml (normal 0-20 pg/ml) of authentic AVP non-apeptide and serum osmolalities were elevated, 315.4 +/- 1.4 mosm/liter (control, 307.3 +/- 1.1), consistent with a state of mild nephrogenic diabetes insipidus. Brain levels of immunoreactive AVP in transgenic mice were 3-4-fold elevated 145 +/- 15 ng/g versus 31 +/- 7 (controls). Although immunoreactive AVP in livers and intestines, and to some extent kidneys, consisted predominantly of unprocessed precursors, in brain and pancreas greater than 90% of AVP consisted of processed bioactive nonapeptide, as determined by chromatography and measurements of cAMP-generation in LLC-PK1 cells. Immunocytochemistry localized immunoreactive AVP to the exocrine pancreas and to the magnacellular neurons (SON and PVN) of the hypothalamus. Expression of the fusion gene in the hypothalamus was further demonstrated by Northern analyses of fusion gene specific transcripts and in situ histohybridization. Although the fusion gene contained only 35 base pairs of 5'-flanking DNA of the ppAVP-NPII gene, a tentative neuronal cell-specific expression element, -17GCCCAG-CC-10 resides in this sequence and may confer neuron-specific expression to the fusion gene.
 ...
PMID:Metallothionein-vasopressin fusion gene expression in transgenic mice. Nephrogenic diabetes insipidus and brain transcripts localized to magnocellular neurons. 280 95

We examined the effects of oxytocin on renal tubular epithelial LLC-PK1 cells. In cells loaded with Fura 2, we found that 1 microM oxytocin induced a rapid increase in cytosolic free [Ca2+]i from 120 nM to 250 nM within 12 sec. [Ca2+]i then decreased and leveled at 148 nM. Calcium was mobilized from intra- and extra-cellular sources. Oxytocin-induced calcium mobilization was dose dependent (EC50 between 5 and 30 nM). Oxytocin also stimulated calcium efflux which was blocked by the selective oxytocin antagonist KB-5-21. Calcium mobilization was a likely consequence of enhanced phosphatidylinositol turnover, because oxytocin rapidly increased the formation of inositol phosphates including Ins1,4,5P3. Calcium transients were induced by oxytocin and the oxytocin selective analog AM-2-40 and blocked by the oxytocin-selective antagonist KB-5-21. Lysine vasopressin, the selective V2 agonist dDAVP, and the V1-selective agonist SK&F 105349 were at least 10- to 100-fold less potent than oxytocin and exhibited only partial agonist activity. Using peptide analogs, a poor correlation was found between antagonism of oxytocin-induced calcium transients of LLC-PK1 cells and pig kidney V2 and rat liver V1 receptor affinity. These data indicate that oxytocin-induced calcium transients in LLC-PK1 cells were not mediated by V1 or V2 vasopressin receptors, but by oxytocin receptors. However, the poor correlation between antagonism at the LLC-PK1 receptors and the rat uterus oxytocin receptors suggests marked differences in antagonist recognition. We have also identified specific, saturable, high affinity oxytocin-binding sites of low density on intact LLC-PK1 cells (KD = 1.9 nM; Bmax = 3.2 fmol/10(6) cells). The relative analog affinities for these binding sites correlated well with their effects on oxytocin-induced calcium transients. We conclude that in LLC-PK1 cells, oxytocin stimulates a transient rise in cytosolic free [Ca2+]i and the formation of inositol phosphates, including Ins1,4,5P3. The effects on [Ca2+]i probably are not mediated by V1 and V2 vasopressin receptors, but by putative oxytocin receptors.
 ...
PMID:Oxytocin induces a transient increase in cytosolic free [Ca2+] in renal tubular epithelial cells: evidence for oxytocin receptors on LLC-PK1 cells. 282 15

The effect of atrial natriuretic peptide (ANP), arginine vasopressin (AVP), and oxytocin (OT) on cAMP and cGMP accumulation was investigated in LLC-PK1 kidney epithelial cells. The addition of ANP, AVP, and OT to intact cells produced a time- and concentration-dependent increase in cGMP accumulation. ANP produced a 1.7-fold increase in cGMP at 10 pM and a maximal 28-fold increase in cGMP at 1 microM. ANP had no effect on basal or AVP-induced stimulation of cAMP accumulation. OT was 10-fold more potent than AVP at increasing cGMP levels, producing a 2.1-fold increase in cGMP at 0.1 nM, whereas AVP was 100-fold more potent at increasing cAMP levels. At a concentration of 1 microM, AVP and OT produced a maximal 12 to 14-fold increase in cGMP, while OT and AVP produced 50- and 90-fold increase in cAMP, respectively. The selective OT agonist [Thr4, Gly7]oxytocin was very effective at increasing cGMP, but not at increasing cAMP levels. The V2-vasopressin agonist [deamino-Pen1,Val4, D-Arg8]vasopressin did not increase cGMP levels, but produced a 20-fold increase in cAMP levels. The addition of ANP together with either AVP or OT produced an additive increase in cGMP content. Simultaneous addition of AVP and OT did not lead to a greater increase in cAMP or cGMP levels. These results suggest that the AVP- and OT-induced increase in cGMP is mediated by OT receptors, whereas the increase in cAMP is probably mediated by vasopressin receptors. ANP increased the activity of particulate guanylate cyclase by 6-fold, while AVP and OT has no effect on particulate guanylate cyclase activity. The relatively selective inhibitor of soluble guanylate cyclase, methylene blue, had no effect on the ANP-induced increase in cGMP content in intact cells, but produced a 50% inhibition of the increase in cGMP by AVP and OT. Methylene blue did not alter the stimulation of cAMP by AVP or OT. These results demonstrate that ANP, AVP, and OT increase cGMP in LLC-PK1 kidney epithelial cells. The increase in cGMP by ANP is mediated by particulate guanylate cyclase, whereas AVP and OT probably increase cGMP by interacting with OT receptors coupled to soluble guanylate cyclase.
 ...
PMID:Atrial natriuretic peptide, oxytocin, and vasopressin increase guanosine 3',5'-monophosphate in LLC-PK1 kidney epithelial cells. 289 98

Using a variety of peptide analogues of oxytocin (OT) and Arg8-vasopressin (AVP), OT-mediated induction of urokinase-type plasminogen activator (uPA) was examined in LLC-PK1 renal epithelial cells, which possess distinct high-affinity receptors of both the OT- and vasopressin renal (V2-) types. OT or OT-receptor specific agonists induced concentration-dependent cAMP synthesis, activation of the cAMP-dependent protein kinase (cAMP-PK) and uPA production consistent with their respective binding affinities for the V2- and not the OT-receptor. OT-mediated uPA induction could be inhibited in a concentration-dependent fashion by coincubation with a V2/V1-receptor specific antagonist, but not by an OT-receptor specific antagonist. Results implied that stimulation of cAMP- and uPA responses in LLC-PK1 cells by OT was V2-receptor-mediated.
 ...
PMID:Oxytocin induced cAMP-dependent protein kinase activation and urokinase-type plasminogen activator production in LLC-PK1 renal epithelial cells is mediated by the vasopressin V2-receptor. 838 Feb 70

[Arg8]vasopressin and oxytocin are the two main members of the neurohypophysial hormone family found to be present in nearly all mammals. [Lys8]vasopressin ([Lys8]VP) has been identified as the antidiuretic hormone in pig and some marsupial families. The porcine-derived kidney epithelial cell line, LLC-PK1, expresses both [Lys8]VP receptors coupled to the activation of adenylate cyclase (V2 receptors) and oxytocin receptors. Here we report the molecular cloning of the V2 [Lys8]VP receptor and the oxytocin receptor from LLC-PK1 cells. The cloned V2 [Lys8]VP receptor differs from human and rat V2 [Arg8] receptors mainly in its N-terminal region, in residues located in the extracellular loops and in intracellular phosphorylation sites. When expressed in COS7 cells, the V2 [Lys8]VP receptor exhibits the relative order of ligand affinity [Lys8]VP = [Arg8]VP >> 1-deamino[D-Arg8]VP > or = oxytocin and adenylate-cyclase stimulation, expected for the porcine V2 [Lys8]VP receptor but different from V2 [Arg8]VP receptors. Adenylate-cyclase activation by [Lys8]VP was inhibited in COS7 cells by a V2 antagonist. The cloned oxytocin receptor exhibits in COS7 cells a ligand specificity typical of mammalian oxytocin receptors. mRNA-distribution analysis revealed a single 5.5-kb transcript in the uterus from pregnant guinea pig.
 ...
PMID:Molecular cloning and functional characterization of V2 [8-lysine] vasopressin and oxytocin receptors from a pig kidney cell line. 839 86


1 2 Next >>