bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of P1 and P2Y purinoceptor antagonists on endothelium‐dependent and ‐independent relaxations of rat mesenteric artery to GTP and guanosine
Authors: Vuorinen Pauli , Wu Xiumin , Arvola Pertti , Vapaatalo Heikki , Pörsti Ilkka 
Published: July 2012

Guanosine 5′‐triphosphate (GTP) and guanosine can relax both endothelium‐intact and ‐denuded arterial preparations. In the present work the P1 and P2Y purinoceptor antagonists, 8‐phenyltheophylline and reactive blue 2, respectively, were used to study the mechanisms of relaxation responses induced by GTP, guanosine, adenosine 5′‐triphosphate (ATP) and adenosine in noradrenaline‐precontracted rat mesenteric artery rings.
GTP (10 μm – 1 mm) dose‐dependently relaxed endothelium‐intact mesenteric artery rings and also induced moderate relaxation responses in endothelium‐denuded preparations. Pretreatment of the rings with 8‐phenyltheophylline (10 μm) or reactive blue 2 (10 μm) did not attenuate the relaxant effect of GTP.
Guanosine (10 μm – 1 mm) relaxed both endothelium‐intact and ‐denuded artery rings in a dose‐dependent manner. The presence of 8‐phenyltheophylline or reactive blue 2 had no effects on guanosine‐induced relaxations.
ATP‐induced (0.1 μm – 0.1 mm) relaxation of endothelium‐intact artery rings was attenuated by reactive blue 2 while 8‐phenyltheophylline was ineffective. ATP also relaxed endothelium‐denuded artery rings and this relaxation was inhibited by 8‐phenyltheophylline, but not by reactive blue 2.
Adenosine‐induced (10 μm–1 mm) relaxation of endothelium‐intact and ‐denuded artery rings was attenuated by the presence of 8‐phenyltheophylline, but not of reactive blue 2.
In conclusion, the endothelium‐dependent and ‐independent relaxations of rat mesenteric arteries to GTP and guanosine are not mediated via P1 and P2Y purinoceptors. Therefore, these results support our previous suggestion on the presence of a novel guanine nucleotide‐specific receptor, a putative PG receptor, on both endothelial and smooth muscle cells, which may participate in the regulation of arterial tone.
Characterization of the prostaglandin E2 sensitive (EP)‐receptor in the rat isolated trachea
Authors: Lydford S.J. , McKechnie K. 
Published: July 2012

Using a range of natural and synthetic prostanoid receptor agonists and antagonists, we have shown that the rat isolated trachea contains a heterogeneous population of prostaglandin receptor sub‐types mediating both relaxation and contraction of the smooth muscle. Prostaglandin E2 (PGE2) elicits smooth muscle relaxation of pre‐contracted preparations, the responses being well defined, with a mean potency (p[A50]) of 7.81 ± 0.05.
11‐deoxy PGE1 16,16‐dimethyl PGE2 and misoprostol were all full agonists at this receptor, whilst AH13205 was a low potency agonist, and sulprostone was inactive.
The EP1 receptor antagonist, AH6809 (5 μm), and the selective DP receptor antagonist, BW A868C (0.1 μm), had no significant effect on the concentration‐effect (E/[A]) curves to PGE2.
The putative EP4‐receptor antagonist, AH23848B, produced non‐competitive antagonism of the PGE2 response curves; pA2 values of 5.07 ± 0.15 and 5.24 ± 0.19 were obtained at concentrations of 30 μm and 100 μm respectively.
The synthetic thromboxane A2 mimetic, U46619, caused smooth muscle contractions, with a mean p[A50] of 6.90 ± 0.11. This response was antagonized by the TP receptor antagonist, GR32191B, yielding a mean pA2 of 8.31.
At concentrations of 1 μm and above, prostaglandin D2 (PGD2) and the IP‐receptor agonist, cicaprost, generally elicited concentration‐dependent relaxations of the rat trachea. Prostaglandin F2α (PGF2α) was without affinity or efficacy.
These data suggest that the rat isolated trachea contains EP‐receptors, TP‐receptors, and few, if any, DP, IP or FP‐receptors. The inactivity of sulprostone (EP3/EP1 receptor selective) and the low potency of AH13205 (EP2‐receptor selective) suggest that the rat trachea contains an atypical EP‐receptor that does not conform to the current classification system.
Block of ATP‐sensitive K+ channels in isolated mouse pancreatic β‐cells by 2,3‐butanedione monoxime
Authors: Smith Paul A. , Williams Beatrice A. , Ashcroft Frances M. 
Published: July 2012

The patch‐clamp technique has been used to examine the action of the chemical phosphatase 2,3‐butanedione monoxime (BDM) on ATP‐sensitive K+ channels (KATP‐channels) from mouse isolated pancreatic β‐cells in the absence of ATP and Mg2+.
BDM reversibly inhibited whole‐cell KATP‐currents with a concentration for half maximal inhibition (Ki) of 15 ± 1 mm and a Hill coefficient (n) of 2.5 ± 0.2 (n = 4).
In outside‐out patches, external BDM reversibly reduced the activity of single KATP‐channels with an affinity similar to that observed in whole‐cell recordings (Ki = 11 ± 3 mm, n = 2.0 ± 0.3, n = 7). In inside‐out patches, internally applied BDM also reversibly blocked the activity of KATP‐channels (Ki = 31 ± 2 mm, n = 2.2 ± 0.4, n = 8). In both excised patch configurations, BDM decreased the mean open life‐time and the burst duration, thereby producing a decrease in the channel open probability. The drug had no effect on the short intraburst closed times.
BDM had no effect on the single‐channel current amplitude.
The results suggest that BDM blocks the KATP‐channel directly, by mechanisms independent of channel dephosphorylation.
Stimulation of chloride secretion by P1 purinoceptor agonists in cystic fibrosis phenotype airway epithelial cell line CFPEo‐
Authors: Chao Anthony C. , Zifferblatt Jonathan B. , Wagner John A. , Dong Y.‐J. , Gruenert Dieter C. , Gardner Phyllis 
Published: July 2012

P1 purinoceptor agonists like adenosine have been shown to stimulate Cl−1 transport in secretory epithelia. In the present study, we investigated whether P1 agonist‐induced Cl−1 secretion is preserved in cystic fibrosis airway epithelium and which signalling mechanism is involved. The effects of purinoceptor agonists on Cl−1 secretion were examined in a transformed cystic fibrosis airway phenotype epithelial cell line, CFPEo‐.
Addition of adenosine (ADO; 0.1 – 1 mm) markedly increased 125I efflux rate. The rank order of potency of purinoceptor agonists in stimulating 125I efflux was ADO > AMP > ADP ≃ ATP. A similar order of potency was seen in transformed cystic fibrosis nasal polyp cells, CFNPEo‐ (ADO > ATP > AMP > ADP). These results are consistent with the activation of Cl−1 secretion via a P1 purinoceptor.
The P1 agonists tested (at 0.01 and 0.1 mm) revealed a rank order of potency of 5′‐N‐ethylcarboxamine adenosine (NECA) > 2‐chloro‐adenosine (2‐Cl‐ADO) > R‐phenylisopropyl adenosine (R‐PIA).
The known potent A2 adenosine receptor (A2AR) agonist, 5′‐(N‐cyclopropyl) carboxamidoadenosine (CPCA, 2 μm) but not the A1 adenosine receptor agonist, N6‐phenyl adenosine (N6‐phenyl ADO, 10 μm) markedly increased 125I efflux rate (baseline, 5.9 ± 2.0% min−1, + CPCA, 10.9 ± 0.6% min−1; P < 0.01). The stimulant effect of CPCA (10 μm) was abolished by addition of the A2AR antagonist 3,7‐dimethyl‐1‐propargylxanthine (DMPX) (100 μm; reported K1 = 11 ± 3 μm). These results favour the involvement of A2AR.
ADO (0.1 – 1 mm) and CPCA (2 μm) both induced a marked increase in intracellular [Ca2+] ([Ca2+]i); the effect of the latter was again abolished by pretreatment of the cells with DMPX. By contrast, N6‐phenyl ADO did not affect [Ca2+]i.
In patch‐clamp experiments, ADO (1 mm) induced an outwardly‐rectified whole‐cell Cl−1 current (baseline, 2.5 ± 0.8 pA pF−1, + ADO, 78.4 ± 23.8 pA pF−1; P < 0.02), which was largely inhibited in cells internally perfused with a selective inhibitory peptide of the multifunctional Ca2+/calmodulin‐dependent protein kinase, CaMK [273–302] (20 μm), as compared to a control peptide, CaMK [284–302]. Addition of BAPTA (10 mm), a Ca2+ chelator, to the perfusion pipette also abolished the ADO‐elicited Cl−1 current.
In conclusion, our results suggest that A2AR participates in regulation of airway Cl−1 secretion via a Ca2+‐dependent signalling pathway, which involves CaMK and appears to be at least partially conserved in cystic fibrosis airway epithelial cells.
Differences in the effects of NK1‐receptor antagonists, (±)‐CP 96,345 and CP 99,994, on agonist‐induced responses in guinea‐pig trachea
Authors: Longmore J. , Razzaque Z. , Shaw D. , Hill R.G. 
Published: July 2012

The effects of the NK1‐receptor antagonists, (±)‐CP 96,345 and CP 99,994, on NK1‐agonist evoked contractions were compared in isolated rings of guinea‐pig tracheal smooth muscle.
(±)‐CP 96,345 and CP 99,994 were similarly effective in antagonizing responses evoked by septide, whereas CP 99,994 was more effective than (±)‐CP 96,345 in inhibiting responses evoked by [Sar9Met11(O2)] substance P.
These results suggest that responses to septide and [Sar9Met11(O2)] substance P may be operated via different populations of NK1‐receptors.
Attenuation by chlormethiazole administration of the rise in extracellular amino acids following focal ischaemia in the cerebral cortex of the rat
Authors: Baldwin H.A. , Williams J.L. , Snares M. , Ferreira T. , Cross A.J. , Green A.R. 
Published: July 2012

In vivo microdialysis has been used to investigate the concentration of various amino acids and lactate in the extracellular fluid of the rat cortex following focal ischaemia, the probe being placed in the core of the infarct area.
An ischaemic infarct was produced in the cortex by use of a photochemical dye (Rose Bengal) and light irradiation. There was a marked increase in lactate concentration (300%) over the next 4 h. Substantial increases were also seen in the concentration of the excitatory (glutamate and aspartate), inhibitory (GABA and taurine) and other amino acids (serine, alanine, asparagine).
Administration of chlormethiazole (200 mg kg−1, i.p.) 5 min after the onset of ischaemia reduced the ischaemia‐induced neurodegeneration by approximately 30%, measured histologically 24 h later.
Chlormethiazole (200 mg kg−1, i.p.) administration also reduced the rise in the concentration of lactate and all the amino acids by between 30–60% during the first 4 h after the onset of ischaemia.
Analysis of the time course of the amino acid changes suggested that chlormethiazole is not neuroprotective because of the inhibition of excitatory amino acid release but rather that the attenuated rise in the concentration of all the amino acids is reflective of neuroprotection and therefore decreased cell death.
This conclusion was supported by the observation that the enhanced efflux of glutamate from slices of cerebral cortex which had been induced by incubation of the slices in an hypoxic medium was unaltered by the presence of a high concentration of chlormethiazole (1 mm) in the medium.
Overall the data strengthen the evidence for the neuroprotective effect of chlormethiazole in this model of focal ischaemia.
Effects of naftidrofuryl oxalate on microsphere embolism‐induced decrease in regional blood flow of rat brain
Authors: Miyake Keiko , Takagi Norio , Takeo Satoshi 
Published: July 2012

The purpose of the present study was to determine whether naftidrofuryl oxalate (naftidrofuryl), a vasodilator, is capable of improving brain regional blood flow of animals in sustained ischaemia.
Cerebral ischaemia was induced by injecting 900 microspheres (48 μm in diameter) into the right internal carotid artery of rats. Cerebral blood flow of brain regions was measured by a hydrogen clearance method on the 3rd, 7th and 28th days after the onset of ischaemia. Ischaemic animals were treated with naftidrofuryl, 15 mg kg−1 day−1 i.p., from the first to 28th day.
Microsphere‐embolism caused a sustained decrease in cortical and striatal blood flow over a period of 28 days, whereas hippocampal blood flow was decreased on the 3rd day but not on the 7th or 28th day. On the 3rd day, the striatal and hippocampal but not cortical blood flow of naftidrofuryl‐treated, microsphere‐embolized rats was higher than untreated rats. On the 7th and 28th days, the cortical and striatal blood flow of the treated and untreated animals did not differ.
Brain slices from microsphere‐embolized rats contained areas, which were not stained with triphenyltetrazolium chloride (TTC), to a similar degree on the 3rd, 7th and 28th days, indicating the genesis of cerebral infarction. TTC‐unstained areas of microsphere‐embolized rats that had received naftidrofuryl treatment were smaller than those of untreated rats on the 3rd and 7th days, but not on the 28th day.
The results suggest that naftidrofuryl improves cerebral circulation impaired by microsphere‐induced ischaemia and this higher level of cerebral blood flow of the treated animal may account for the delayed development of cerebral infarction.
Comparative pharmacology of recombinant rat AT1A, AT1B and human AT1 receptors expressed by transfected COS‐M6 cells
Authors: Balmforth Anthony J. , Bryson Susan E. , Alison J. Aylett , Warburton Philip , Ball Stephen G. , Pun Kwok‐Tao , Middlemiss David , Drew G. Michael 
Published: July 2012

Currently available antagonists and agonists cannot distinguish between angiotensin AT1 receptor subtypes.
We synthesized a series of compounds selected on the basis of having the most diverse structural features with respect to losartan (DuP753), the prototype non‐peptide AT1 receptor antagonist. Using a radioligand‐receptor binding assay and membranes prepared from COS‐M6 cells transfected with individual AT1 receptor subtypes, we determined whether any of these compounds could distinguish between the receptor subtypes.
The diversity of the structural features of this series of compounds was reflected by the wide range of affinities (pIC50 values) displayed towards competing with [125I]‐Sar1Ile8 angiotensin II for binding to the AT1 receptors.
Direct comparisons of the pIC50 values of individual compounds for rat AT1A, AT1B and human AT1 receptors revealed only minor differences.
It is concluded that compounds based structurally on losartan are unlikely to distinguish between these receptors.
Relative roles of nitric oxide and cyclo‐oxygenase and lipoxygenase products of arachidonic acid in the contractile responses of rat renal arcuate arteries
Authors: Wu X.C. , Richards N.T. , Michael J. , Johns E. 
Published: July 2012

We have examined the effects of inhibition of nitric oxide synthase, cyclo‐oxygenase and lipoxygenase on the responses of renal arcuate arteries of Wistar rats, with and without endothelium, to noradrenaline, potassium chloride, endothelin‐1, acetylcholine and sodium nitroprusside.
Noradrenaline, potassium chloride and endothelin‐1 caused concentration‐dependent contraction of the vessels. Indomethacin (14 μm) attenuated the contractile response to noradrenaline and to potassium chloride. The inhibitory effect of indomethacin persisted following endothelial removal.
Acetylcholine produced concentration‐dependent relaxation of the vessels which was potentiated by indomethacin (14 μm).
NG‐nitro‐l‐arginine methyl ester (l‐NAME, 100 μm) did not affect the contractile response to either noradrenaline or potassium chloride but abolished relaxation to acetylcholine. In addition, l‐NAME abolished the affects of indomethacin on acetylcholine‐induced relaxation and noradrenaline‐ and potassium chloride‐induced contraction.
BWC755C attenuated noradrenaline and potassium chloride‐induced contraction. This effect persisted in the presence of indomethacin.
In vessels pretreated with CHAPS, BW755C inhibited both noradrenaline and potassium chloride‐induced contraction. In these vessels BW755C had no additional inhibitory effect to indomethacin on noradrenaline‐ and potassium‐induced contraction.
Inhibition of nitric oxide synthase with l‐NAME (100 μm) attenuated the effect of BW755C on noradrenaline‐ and potassium‐induced contraction.
BW755C alone did not affect endothelium‐dependent relaxation as assessed by the response to acetylcholine. However, in the presence of indomethacin, BW755C inhibited acetylcholine‐induced relaxation.
BW755C did not affect endothelium‐independent relaxation as assessed by the response to sodium nitroprusside in vessels with or without endothelium.
These data support the existence of two vasoconstrictor products of arachidonic acid released during contraction of renal arcuate arteries with noradrenaline and potassium chloride. A cyclo‐oxygenase product which appears to be endothelium‐independent and the other an endothelium‐dependent lipoxygenase product.
The renal handling of dopamine originating from l‐DOPA and γ‐glutamyl‐l‐DOPA
Authors: Pestana M. , Soares‐da‐Silva P. 
Published: July 2012

The formation and outflow of dopamine and its deaminated metabolite 3,4‐dihydroxyphenylacetic acid (DOPAC) was studied in cortical fragments of the rat kidney loaded with l‐β‐3,4‐dihydroxyphenylalanine (l‐DOPA) or γ‐glutamyl‐l‐DOPA (GluDOPA). Dopamine and DOPAC in the tissues and in the effluent were assayed by means of h.p.l.c. with electrochemical detection.
In rats given 30 mg kg−1 l‐DOPA, tissue and outflow levels of both dopamine and DOPAC were 3 fold those observed with a lower dose of l‐DOPA (10 mg kg−1). In rats given GluDOPA (16.7 mg kg−1) levels of dopamine in renal tissues and in perifusate samples were found to be higher than those obtained with an equimolar dose of l‐DOPA (10 mg kg−1); however, no significant difference was observed for DOPAC. The outflow of both dopamine and DOPAC in kidney slices of rats injected with l‐DOPA (10 and 30 mg kg−1) or GluDOPA (16.7 mg kg−1) was found to decline monophasically with similar slopes of decline. The rate constants of loss (k, min−1) of DOPAC (10 mg kg−1 l‐DOPA, k = 0.0070; 30 mg kg−1 l‐DOPA, k = 0.0087; 16.7 mg kg−1 GluDOPA, k = 0.0080) were 2 to 3 fold those of dopamine (10 mg kg−1 l‐DOPA, k = 0.0027; 30 mg kg−1 l‐DOPA, k = 0.0034; 16.7 mg kg−1 GluDOPA, k = 0.0030). With both precursors the DOPAC/dopamine ratio in perifusate samples were 2.0 fold those in the tissues.
Tissue and outflow levels of dopamine after incubation of renal tissues with l‐DOPA, 50 and 100 μm were found to be lower than those observed with GluDOPA (50 and 100 μm). DOPAC/dopamine ratios in tissues and perifusate samples of experiments performed with l‐DOPA were significantly higher (P < 0.01) than those observed with GluDOPA. The outflow of both dopamine and DOPAC in renal slices incubated with l‐DOPA (50 and 100 μm) were found to decline with time, but presented a biphasic shape. DOPAC/dopamine ratios in perifusate samples were 3 fold that in the tissues with both precursors.
In conclusion, the present results show that both l‐DOPA and GluDOPA give origin to substantial amounts of dopamine and the newly‐formed amine undergoes considerable deamination to DOPAC. However, dopamine originating from GluDOPA was less deaminated than that resulting from l‐DOPA; it appears that this different behaviour may concern aspects related to the formation of the amine and also those related to its deamination and disposition, namely the processes involved in the access of newly‐formed dopamine to MAO.
Effects of dietary marine oil supplementation on reactivity of human buttock subcutaneous arteries and forearm veins in vitro
Authors: Chin Jaye P.F. , Kaye David M. , Hurlston Robyn M. , Angus James A. , Jennings Garry L. , Dart Anthony M. 
Published: July 2012

The vascular reactivity of resistance arteries isolated from gluteal skin biopsies and veins isolated from forearms of subjects fed marine oils were examined.
Twenty seven healthy adult males were randomly allocated to one of two different treatment groups. The first group received maxEPA (eicosapentaenoic acid 0.178 g g−1; docosahexaenoic acid 0.116 g g−1) capsules 10 g per day for 28 days while the second group received an equivalent amount of mixed oil placebo capsules. Biopsies were performed on day 29 (13 for gluteal sections; 14 for forearm vein biopsies). Subcutaneous arteries and veins were mounted in myographs and standard organ baths, respectively.
The internal diameter of the subcutaneous arteries at a calculated transmural pressure of 100 mmHg averaged 183.7 ± 10.3 μm in the maxEPA group and 182.6 ± 19.8 μm in the placebo controls. Arteries from subjects on maxEPA demonstrated increased sensitivity to angiotensin II (maxEPA vs placebo: – log EC50 (m) − 8.36 ± 0.18 vs − 7.91 ± 0.14) but not to noradrenaline or 5‐hydroxytryptamine. Concentration‐response curves to acetylcholine, substance P and sodium nitroprusside obtained for noradrenaline precontracted vessels were unaltered with marine oil treatment as was the concentration‐response curve to calcium in K+‐depolarized vessels.
Vein internal diameter at a calculated transmural pressure of 20 mmHg averaged 3.06 ± 0.23 mm in the maxEPA group and 2.96 ± 0.89 in the placebo group. Responses to noradrenaline, 5‐hydroxytryptamine, angiotensin II and endothelin‐1 were obtained in the absence and presence of indomethacin (1 μm) in veins from both maxEPA and placebo‐treated subjects. Neither dietary supplementation with marine oils nor indomethacin had any effect on the responses obtained to these agonists.
The major finding of the present study was that in general, maxEPA supplementation did not affect responses to various vasoactive substances on isolated subcutaneous arteries or forearm veins. An exception was the observation of an enhanced response to angiotensin II in subcutaneous resistance arteries studied in vitro. This effect was selective for angiotensin II and was not apparent in veins isolated from the forearm.
Differences in sensitivity of rat mesenteric small arteries to agonists when studied as ring preparations or as cannulated preparations
Authors: Buus N.H. , VanBavel E. , Mulvany M.J. 
Published: July 2012

Pharmacological experiments on vascular tissue are normally performed on isometric ring or strip preparations. The aim of this study was to compare the isometric characteristics with the characteristics obtained if vessels were examined under the more physiologically appropriate isobaric condition.
Rat mesenteric small arteries were mounted either on two steel wires for isometric force measurement (wire‐myograph) or cannulated for measurement of the internal diameter under isobaric conditions (pressure‐myograph).
The passive pressure‐diameter characteristics of the small arteries were similar on the wire‐ and pressure‐myograph (using the Laplace relation to convert wall tension‐internal circumference data from the wire‐myograph to effective pressure‐diameter characteristics).
In cumulative concentration‐response experiments with noradrenaline and phenyelphrine, the threshold concentration was 8–10 times lower, and the EC50‐concentration was 4–5 times lower, in the pressure myograph compared to the wire‐myograph. Thus vessels were not only more sensitive on the pressure myograph, but the slopes of the concentration‐response curves were less steep. Similar experiments with vasopressin also showed this difference in the threshold‐concentration and slope, but EC50 concentrations were similar.
Cumulative concentration‐response experiments with K+ showed no difference either in EC50 or in slope on the wire‐ and pressure‐myographs.
On the wire‐myograph, some vessels were stretched longitudinally (to mimic the longitudinal stretch which had to be used in the pressure‐myograph to avoid buckling). Such stretch did not affect the passive characteristics.
The differences between the EC50 determined on the wire‐ and pressure‐myographs as regards noradrenaline and phenylephrine were eliminated when neuronal noradrenaline uptake was inhibited by denervation. However, the slope of the concentration‐response curves on the wire‐myograph was not affected by denervation.
When vessels were exposed to cocaine (3 μm) the noradrenaline concentration‐response curves were the same on the wire‐ and pressure‐myographs as regards both EC50 and slope.
On the wire‐myograph, the calcium antagonist, methoxyverapamil, (D600) reduced the maximal contractile effect of noradrenaline by 50%, but on the pressure‐myograph D600 did not affect the maximal response.
The present results show that results obtained from vascular tissue under isometric conditions may differ substantially from the characteristics which would be obtained under isobaric conditions.