bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of sodium on agonist efficacy for G‐protein activation in μ‐opioid receptor‐transfected CHO cells and rat thalamus
Authors: Selley Dana E , Cao Cheng‐Chun , Liu Qixu , Childers Steven R 
Published: January 2005

Sodium ions inhibit spontaneous Gi/Go‐coupled receptor activity and promote agonist‐induced responses in vitro. The effects of sodium on the relative efficacy of opioid agonists for G‐protein activation was measured by guanosine‐5′‐O‐(γ‐35S)‐triphosphate ([35S]‐GTPγS) binding in membranes from two μ‐opioid receptor‐containing systems: CHO cells stably transfected with mouse μ receptors (mMOR‐CHO cells) and rat thalamus.
NaCl inhibited basal [35S]‐GTPγS binding in both systems, and this effect was partially mimicked by KCl. In mMOR‐CHO membranes, net [35S]‐GTPγS binding stimulated by partial but not full agonists was inhibited by NaCl with a potency that was inversely proportional to agonist efficacy. Monovalent cations were required for agonist‐stimulated [35S]‐GTPγS binding in this system, and increasing NaCl concentrations magnified relative efficacy differences among agonists.
In thalamic membranes, which contain a lower receptor:G‐protein ratio than mMOR‐CHO cells, similar monovalent cation effects were observed, with two exceptions: (1) [35S]‐GTPγS binding stimulated by both full and partial agonists was inhibited by NaCl; and (2) monovalent cations were not required to observe agonist‐stimulated [35S]‐GTPγS binding.
Basal [35S]‐GTPγS binding stimulated by the absence of monovalent cations resembled that of agonist‐stimulated binding and was blocked by pretreatment of mMOR‐CHO cells with pertussis toxin.
These results indicate that sodium inhibits spontaneous and agonist‐occupied μ receptor‐mediated G‐protein activation in a manner inversely proportional to the efficacy of the agonist, and that spontaneous μ receptor activity and the relative efficacy of partial agonists acting at these receptors are both increased by increases in the stoichiometric ratio of receptors:G‐proteins.

British Journal of Pharmacology (2000) 130, 987–996; doi:10.1038/sj.bjp.0703382
Opposite effects of flurbiprofen and the nitroxybutyl ester of flurbiprofen on apoptosis in cultured guinea‐pig gastric mucous cells
Authors: Johal Kamaljit , Hanson Peter J 
Published: January 2005

The nitric oxide (NO)‐donating nitroxybutyl ester of flurbiprofen (NO‐flurbiprofen), shows reduced gastro‐intestinal toxicity relative to flurbiprofen. NO may exert either pro‐ or anti‐apoptotic effects, while non‐steroidal anti‐inflammatory drugs may induce apoptosis. The aim of the present work was therefore to compare the effects of flurbiprofen and NO‐flurbiprofen on apoptosis in guinea‐pig gastric mucous cells.
Apoptotic activity was assessed by assay of caspase activity and from the fragmentation and condensation of nuclei.
Incubation with flurbiprofen for 24 h produced a concentration‐dependent induction of apoptosis in cells attached to the culture plate (caspase 3‐like activity increased by 257% at 500 μM), while NO‐flurbiprofen inhibited basal apoptosis (caspase 3‐like activity decreased by 71% at 500 μM).
Caspase activity and nuclear fragmentation were substantially increased in cells that had spontaneously detached from the culture plate. NO‐flurbiprofen inhibited caspase activity (55% at 500 μM) but not nuclear fragmentation in these detached cells.
NO flurbiprofen inhibited the activation of apoptosis by 25 μM C6‐ceramide in cells attached to the culture plate.
Inhibition of caspase activity by NO‐flurbiprofen was detectable after 6 h of incubation with intact cells, but by contrast with the NO‐donor S‐nitrosyl‐N‐acetyl‐penicillamine, was not demonstrable with cell homogenates.
Activation of caspase 3‐like activity by flurbiprofen was slow (>6 h incubation needed) and was inhibited by cycloheximide.
The presence of a nitroxybutyl ester moiety on flurbiprofen prevents the pro‐apoptotic activity of the parent compound and may contribute to the reduced gastro‐intestinal toxicity of NO‐flurbiprofen.

British Journal of Pharmacology (2000) 130, 811–818; doi:10.1038/sj.bjp.0703383
Role of A2A‐adenosine receptor activation for ATP‐mediated coronary vasodilation in guinea‐pig isolated heart
Authors: Erga Knut Ståle , Seubert Christoph N , Liang Hui‐Xiu , Wu Lin , Shryock John C , Belardinelli Luiz 
Published: January 2005

Adenosine‐5′‐triphosphate (ATP) and adenosine are potent coronary vasodilators. ATP is rapidly converted to adenosine by ectonucleotidases. We examined whether coronary vasodilation caused by exogenous ATP is mediated by P2 receptor activation or by A2A‐adenosine receptor activation.
Effects of interventions on coronary conductance were determined by measuring coronary perfusion pressure in guinea‐pig isolated hearts perfused at a constant flow of 10 ml min−1.
ATP and adenosine both caused sustained, concentration‐dependent increases of coronary conductance. Maximal responses to both agonists were equivalent. The values of pD2 (±s.e.mean) for ATP and adenosine were 6.68±0.04 and 7.06±0.05, respectively. Adenosine was significantly more potent than ATP (P<0.0001, n=10).
The values of pIC50 for the selective A2A‐adenosine receptor antagonist SCH58261 to antagonize equivalent responses to ATP and adenosine were 8.28±0.08 and 8.28±0.06 (P=0.99, n=6), respectively.
The non‐selective adenosine receptor antagonists xanthine amine congener (XAC) and CGS15943 antagonized similarly the equivalent vasodilations caused by ATP (pIC50 values 7.48±0.04 and 7.45±0.06, respectively) and adenosine (pIC50 values 7.37±0.13 and 7.56±0.11).
In contrast to ATP and adenosine, the two P2 agonists 2‐methylthio‐ATP and uridine‐5′‐triphosphate failed to cause stable increases of coronary conductance, caused desensitization of vasodilator responses, and were not antagonized by SCH 58261, 8‐parasulphophenyltheophylline, or XAC.
Glibenclamide attenuated coronary vasodilations caused by ATP and adenosine by 88 and 89%, respectively, but failed to attenuate those caused by 2‐methylthio‐ATP.
These results strongly suggest that sustained, submaximal coronary vasodilation caused by exogenous ATP is entirely mediated by adenosine acting upon A2A‐adenosine receptors.

British Journal of Pharmacology (2000) 130, 1065–1075; doi:10.1038/sj.bjp.0703386
The involvement of intracellular Ca2+ in 5‐HT1B/1D receptor‐mediated contraction of the rabbit isolated renal artery
Authors: Hill P B , Dora K A , Hughes A D , Garland C J 
Published: January 2005

5‐Hydroxytryptamine1B/1D (5‐HT1B/1D) receptor coupling to contraction was investigated in endothelium‐denuded rabbit isolated renal arteries, by simultaneously measuring tension and intracellular [Ca2+], and tension in permeabilized smooth muscle cells.
In intact arterial segments, 1 nM–10 μM 5‐HT failed to induce contraction or increase the fura‐2 fluorescence ratio (in the presence of 1 μM ketanserin and prazosin to block 5‐HT2 and α1‐adrenergic receptors, respectively). However, in vessels pre‐exposed to either 20 mM K+ or 30 nM U46619, 5‐HT stimulated concentration‐dependent increases in both tension and intracellular [Ca2+].
1 nM–10 μM U46619 induced concentration‐dependent contractions. In the presence of nifedipine (0.3 and 1 μM) the maximal contraction to U46619 (10 μM) was reduced by around 70%. The residual contraction was abolished by the putative receptor operated channel inhibitor, SKF 96365 (2 μM).
With 0.3 μM nifedipine present, 100 nM U46619 evoked similar contraction to 30 nM U46619 in the absence of nifedipine, but contraction to 5‐HT (1 nM–10 μM) was abolished.
In permeabilized arterial segments, 10 mM caffeine, 1 μM IP3 or 100 μM phenylephrine, each evoked transient contractions by releasing Ca2+ from intracellular stores, whereas 5‐HT had no effect. In intact arterial segments pre‐stimulated with 20 mM K+, 5‐HT‐evoked contractions were unaffected by 1 μM thapsigargin, which inhibits sarco‐ and endoplasmic reticulum calcium‐ATPases.
In vessels permeabilized with α‐toxin and then pre‐contracted with Ca2+ and GTP, 5‐HT evoked further contraction, reflecting increased myofilament Ca2+‐sensitivity.
Contraction linked to 5‐HT1B/1D receptor stimulation in the rabbit renal artery can be explained by an influx of external Ca2+ through voltage‐dependent Ca2+ channels and sensitization of the contractile myofilaments to existing levels of Ca2+, with no release of Ca2+ from intracellular stores.

British Journal of Pharmacology (2000) 130, 835–842; doi:10.1038/sj.bjp.0703387
Participation of kinins in the captopril‐induced inhibition of intimal hyperplasia caused by interruption of carotid blood flow in the mouse
Authors: Emanueli Costanza , Salis Maria Bonaria , Figueroa Carlos , Chao Julie , Chao Lee , Gaspa Leonardo , Capogrossi Maurizio C , Madeddu Paolo 
Published: January 2005

In the rat balloon injury model, angiotensin‐converting enzyme (ACE) inhibitors prevent vascular remodelling by inhibiting angiotensin II generation and kinin breakdown. We investigated if ACE inhibition also prevents the structural vascular responses to disruption of carotid artery blood flow and if kinin potentiation plays a role in such a protection.
Morphometric analysis of the structural alterations caused by ligation of the left carotid artery was performed 14 days after surgery in J129Sv wild‐type mice (B2+/+) drinking normal tap water or water containing captopril (120 mg kg−1 per day). In addition, the effect of captopril on vascular remodelling was tested in B2+/+ given the bradykinin (BK) B1 receptor antagonist des‐Arg9‐[Leu8]‐BK (DALBK, 50 nmol kg−1 per day, intraperitoneally) or the BK B2 receptor antagonist D‐Arg,[Hyp3,Thi5D‐Tic7,Oic8]‐BK (icatibant, 1 μmol kg−1 per day, intraperitoneally), and in B2 receptor gene knockout mice (B2−/−).
Interruption of blood flow resulted in carotid artery intimal hyperplasia and media thickening in untreated B2+/+, these responses being partially suppressed by captopril. The inhibition of intimal thickening exerted by captopril was reduced in B2+/+ given DALBK or icatibant (P<0.05 for both comparisons) as well as in B2−/− (P<0.05). Neither antagonism of kinin receptors nor disruption of the B2 receptor gene altered the suppressive effect of captopril on media thickening. The protection of vascular wall structure was independent of the reduction in blood pressure by captopril.
These results demonstrate that kinins participate in the inhibitory effect of captopril on intimal hyperplasia via B1 and B2 receptor signalling. Our findings may have important implications in treating vascular remodelling evoked by altered shear stress conditions.

British Journal of Pharmacology (2000) 130, 1076–1082; doi:10.1038/sj.bjp.0703388
Deoxycorticosterone acetate‐salt hypertensive rats display gender‐related differences in ETB receptor‐mediated vascular responses
Authors: Passaglia Rita C A Tostes , David Flavia Lucia , Fortes Zuleica B , Nigro Dorothy , Scivoletto Regina , Catelli de Carvalho Maria Helena 
Published: January 2005

Male DOCA‐salt rats exhibit vasoconstriction upon ETB activation. Because hypertension is less severe in female than male DOCA rats, we hypothesized that female DOCA rats would display attenuated ETB vasoconstrictor responses.
Uninephrectomized Wistar rats received DOCA and drinking water containing NaCl/KCl. Control rats received vehicle and tap water. Systolic blood pressure was higher in male vs female DOCA rats. Responses to endothelin‐1 (ET‐1), IRL‐1620, an ETB agonist, and acetylcholine were evaluated in isolated aortas and in vivo in the mesenteric microcirculation.
Endothelium‐denuded aortas from male, but not female, DOCA rats displayed increased sensitivity to ET‐1. IRL‐1620 contracted aortas from male DOCA rats, but not control or female DOCA aortas. Noradrenaline‐constricted and endothelium‐intact aortas from male, but not female, DOCA rats displayed increased relaxation to IRL‐1620 compared to control aortas.
In vivo, increased vasoconstriction to ET‐1 was observed in male and female DOCA rats. IRL‐1620 induced vasodilation in control rats, but vasoconstriction in male DOCA rats. There were minimal changes in diameter in vessels from female DOCA rats.
The initial fall in blood pressure induced by ET‐1 and IRL‐1620 was attenuated in male DOCA rats. Bosentan, a mixed ETA/ETB receptor antagonist, lowered blood pressure in male and female DOCA rats, but a greater and marked decrease occurred in the male DOCA group.
The gender‐related differences in ET‐1/ETB‐mediated effects both in the vasculature and blood pressure suggest that sex‐related functional up‐regulation of ETB receptors may play a role in the more severe hypertension in male DOCA hypertensive rats.

British Journal of Pharmacology (2000) 130, 1092–1098; doi:10.1038/sj.bjp.0703389
Endothelial dysfunction in diabetes
Authors: De Vriese An S , Verbeuren Tony J , Van de Voorde Johan , Lameire Norbert H , Vanhoutte Paul M 
Published: January 2005

Endothelial dysfunction plays a key role in the pathogenesis of diabetic vascular disease. The endothelium controls the tone of the underlying vascular smooth muscle through the production of vasodilator mediators. The endothelium‐derived relaxing factors (EDRF) comprise nitric oxide (NO), prostacyclin, and a still elusive endothelium‐derived hyperpolarizing factor (EDHF). Impaired endothelium‐dependent vasodilation has been demonstrated in various vascular beds of different animal models of diabetes and in humans with type 1 and 2 diabetes. Several mechanisms of endothelial dysfunction have been reported, including impaired signal transduction or substrate availibility, impaired release of EDRF, increased destruction of EDRF, enhanced release of endothelium‐derived constricting factors and decreased sensitivity of the vascular smooth muscle to EDRF. The principal mediators of hyperglycaemia‐induced endothelial dysfunction may be activation of protein kinase C, increased activity of the polyol pathway, non‐enzymatic glycation and oxidative stress. Correction of these pathways, as well as administration of ACE inhibitors and folate, has been shown to improve endothelium‐dependent vasodilation in diabetes. Since the mechanisms of endothelial dysfunction appear to differ according to the diabetic model and the vascular bed under study, it is important to select clinically relevant models for future research of endothelial dysfunction.British Journal of Pharmacology(2000)130, 963–974; doi:10.1038/sj.bjp.0703393
Sensitivity of Kir6.2‐SUR1 currents, in the absence and presence of sodium azide, to the KATP channel inhibitors, ciclazindol and englitazone
Authors: McKay N G , Kinsella J M , Campbell C M , Ashford M L J 
Published: January 2005

Two electrode voltage clamp and single channel recordings were used to investigate the actions of various ATP‐sensitive K+ (KATP) channel inhibitors on cloned KATP channels, expressed in Xenopus oocytes and HEK 293 cells.
Oocytes expressing Kir6.2 and SUR1 gave rise to inwardly rectifying K+ currents following bath application of 3 mM sodium azide. Inside‐out recordings from non‐azide treated oocytes demonstrated the presence of KATP channels which were activated by direct application of 3 mM azide and 0.1 mM Mg‐ATP.
Tolbutamide inhibited azide‐induced macroscopic Kir6.2‐SUR1 currents, recorded from Xenopus oocytes, with an IC50 value similar to native KATP channels. Ciclazindol and englitazone also inhibited these currents in a concentration‐dependent manner, but with relative potencies substantially less than for native KATP channels.
Single channel currents recorded from inside‐out patches excised from oocytes expressing Kir6.2‐SUR1 currents were inhibited by tolbutamide, Mg‐ATP, englitazone and ciclazindol, in the absence of azide, with potencies similar to native KATP channels. In the presence of azide, Kir6.2‐SUR1 currents were inhibited by englitazone and tolbutamide but not ciclazindol.
Single channel currents derived from Kir6.2Δ26, expressed in HEK 293 cells, were inhibited by ciclazindol and englitazone irrespective of the absence or presence of SUR1.
In conclusion, heterologously expressed Kir6.2 and SUR1 recapitulate the pharmacological profile of native pancreatic β‐cell KATP channels. However, currents induced by azide exhibit a substantially reduced sensitivity to ciclazindol. It is likely that ciclazindol and englitazone inhibit KATP currents by interaction with the Kir6.2 subunit.

British Journal of Pharmacology (2000) 130, 857–866; doi:10.1038/sj.bjp.0703395
Mechanisms of nitric oxide‐independent relaxations induced by carbachol and acetylcholine in rat isolated renal arteries
Authors: Jiang Fan , Li Chun Guang , Rand Michael J 
Published: January 2005

In rat isolated renal artery segments contracted with 0.1 μM phenylephrine and in the presence of the NO synthase inhibitor Nω‐nitro‐L‐arginine methyl ester (L‐NAME), carbachol and acetylcholine produced endothelium‐dependent relaxations. The mechanisms underlying these relaxations were studied.
These relaxations were not affected by ODQ (1H‐[1,2,4]oxadiazolo[4,3,‐a]quinoxalin‐1‐one) or indomethacin. In arteries contracted with 20–30 mM K+, L‐NAME‐resistant relaxations induced by carbachol and acetylcholine were virtually absent.
The Na+‐K+ ATPase inhibitor ouabain reduced these relaxations in a concentration‐dependent manner.
In K+‐free media, addition of K+ (5 mM) produced 90.5±3.9% (n=3) relaxation of phenylephrine‐induced tone. This relaxation was endothelium‐independent and ouabain‐sensitive.
Tetraethylammonium (TEA), charybdotoxin (ChTX) and iberiotoxin (IbTX) reduced the sensitivity of carbachol‐induced relaxations, but did not change the maximal response. These relaxations were not altered by 4‐aminopyridine (4‐AP), glibenclamide or apamin. Acetylcholine (1 μM)‐induced relaxation was reduced by ChTX, but not by TEA or IbTX.
The cytochrome P450 inhibitor miconazole, but not 17‐octadecynoic acid, reduced the sensitivity of carbachol‐induced relaxations, without changing the maximal response.
In conclusion, in rat isolated renal arteries, acetylcholine and carbachol produced a non‐NO/non‐PGI2 relaxation which is mediated by an endothelium‐derived hyperpolarizing factor (EDHF). This factor does not appear to be a cytochrome P450 metabolite. The inhibition by ouabain of these relaxations suggests the possible involvement of Na+‐K+ ATPase activation in EDHF responses, although other mechanisms cannot be totally ruled out.

British Journal of Pharmacology (2000) 130, 1191–1200; doi:10.1038/sj.bjp.0703408
Mechanisms underlying the neurokinin A‐induced contraction of the pregnant rat myometrium
Authors: Shintani Yoshinobu , Nishimura Junji , Niiro Naohisa , Hirano Katsuya , Nakano Hitoo , Kanaide Hideo 
Published: January 2005

Using fura‐PE3 fluorimetry and α‐toxin permeabilization, the characteristics of the contractile responses to neurokinin A (NKA) were determined in the pregnant rat myometrium.
NKA induced contractions in rat myometrium in a concentration‐dependent manner. There were no significant differences in the maximum contractions and EC50 values between the pregnant and non‐pregnant myometrium, however, the contraction of only the former was greatly enhanced in the presence of phosphoramidon (PPAD), an endopeptidase inhibitor.
In the pregnant myometrium, NKA induced sustained increases in [Ca2+]i and tension in normal physiological saline solution, while only small transient increases in [Ca2+]i and tension were observed in Ca2+‐free solution.
Both diltiazem (10 μM) and SK‐F 96365 (10 μM) significantly inhibited the NKA‐induced elevations of [Ca2+]i and tension. The effects were additive when these drugs were used together.
NKA induced a significant leftward shift of the [Ca2+]i‐tension curve obtained by changing the external Ca2+ (0–2.5 mM) during depolarization with high K+ solution. This Ca2+‐sensitizing effect by NKA was also observed in the α‐toxin permeabilized myometrium.
These results indicated that in the pregnant rat myometrium: (1) the responsiveness to NKA increased, although it was masked by the increase in the endopeptidase activity; (2) NKA induced contractions of the myometrium by increasing both [Ca2+]i and the myofilament Ca2+ sensitivity and (3) The NKA‐induced [Ca2+]i elevation was partly due to the intracellular Ca2+ release and mainly due to the Ca2+ influx, which was thought to be through both voltage dependent calcium channels and non‐specification channels.

British Journal of Pharmacology (2000) 130, 1165–1173; doi:10.1038/sj.bjp.0703410
Potassium does not mimic EDHF in rat mesenteric arteries
Authors: Doughty Joanne M , Boyle John P , Langton Philip D 
Published: January 2005

K+ has been proposed to be EDHF in small arteries. We compared ACh‐stimulated, EDHF‐mediated dilatation/relaxation with raised [K+]o in rat mesenteric arteries.
In pressurized arteries, ACh (10 μM) dilated all arteries. Raising [K+]o from 5.88 to 10.58 mM only dilated 30% of arteries. Ba2+ (30 μM) did not affect dilatation to ACh, but abolished 40% of dilatations to raised [K+]o.
If [K+]o was lowered to 1.18 mM, restoring [K+]o to 5.88 mM produced dilatation which was depressed by Ba2+ or ouabain (1 mM). Combined application of Ba2+ and ouabain abolished dilatation. In 1.18 mM K+, dilatation to ACh was depressed by ouabain, but not by Ba2+. Combined application of Ba2+ and ouabain depressed dilatation further. Gap junction inhibitors (Gap‐27; 300 μM and 18‐α‐glycyrrhetinic acid; 100 μM) also depressed dilatation to ACh.
In arteries mounted isometrically, ACh (1 μM) relaxed endothelium intact (+E), but not endothelium denuded (−E) arteries. Raising [K+]o from 5.9–10.9 mM failed to relax all arteries. When [K+]o was lowered to 1 mM, raising [K+]o to 6 mM produced relaxation. In −E arteries, relaxation was unaffected by Ba2+ but abolished by ouabain. In +E arteries, Ba2+ depressed and ouabain abolished relaxation. In +E arteries, with 1 mM K+, ACh relaxation was depressed by ouabain but not Ba2+. The combined application of Ba2+ and ouabain further depressed relaxation.
In summary, both EDHF and raised [K+]o dilate/relax rat mesenteric arteries, though sensitivities to barium and ouabain differ. K+ may be a relaxing factor in this tissue, but its characteristics differ from EDHF. Gap junction inhibitors depress EDHF, implying an important role for myo‐endothelial gap junctions.

British Journal of Pharmacology (2000) 130, 1174–1182; doi:10.1038/sj.bjp.0703412
Leukaemia inhibitory factor (LIF) upregulates excitatory non‐adrenergic non‐cholinergic and maintains cholinergic neural function in tracheal explants
Authors: Knight D A , D'Aprile A C , Spalding L J , Goldie R G , Thompson P J 
Published: January 2005

The effect of leukaemia inhibitory factor (LIF) in modulating cholinergic and sensory nerve function was examined using guinea‐pig tracheal explants. Specific LIF receptors (LIFR) were immunolocalized to both cholinergic and sensory nerves. Release of SP in culture was not influenced by LIF. Similarly, maximum contraction to carbachol (Cmax) was not influenced by LIF. After 3 h, maximum (Emax) eNANC‐induced contraction in controls was 32±2.5% of Cmax. In LIF‐treated preparations, Emax was enhanced to 50±4.5% Cmax (P<0.05). Cholinergic nerve‐induced contractions after 3 h incubation with LIF were similar to control. After 24 h, control Emax was 25±4.5% Cmax (58% smaller than Emax at 3 h). In contrast, in LIF‐treated preparations, Emax was 37±2.5% Cmax, (24% smaller than at 3 h, P<0.05). This did not appear to be due to the effect of LIF on muscarinic M2 receptor expression or function. Thus LIF appears to differentially influence the function of airway nerves and thus may provide an important link between the immune and neural systems. British Journal of Pharmacology (2000) 130, 975–979; doi:10.1038/sj.bjp.0703415