bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of cytoplasmic pH on Ca2+‐stimulated eicosanoid biosynthesis in human platelets
Authors: Edwards Jacqueline S. , Ritter James M. 
Published: July 2012

We have investigated the effect of cytoplasmic pH (pH;) on the relationship between platelet cytoplasmic Ca2+ concentration ([Ca2+]1) and eicosanoid biosynthesis. Stirred gel‐filtered human platelets loaded with fluorescent indicators of Ca2+ and H+ were suspended in balanced salt solutions at 37°C. [Ca2+]i was controlled by calcium ionophore (ionomycin). Increased [Ca2+]i was associated with increased production of thromboxane A2 (TXA2) as determined by radioimmunoassay of its stable hydrolysis product TXB2, and of 12‐hydroxy eicosatetraenoic acid (12‐HETE) measured by high performance liquid chromatography.
Varying pHi with a K+/H+ ionophore (nigericin) in platelets suspended in K+ rich solutions of pH 6.8, 7.4 or 7.8 with subsequent resuspension in solution of pH 7.4 containing albumin (1 g 1−1) and Ca2+ (mM) resulted in pH1 of 6.72 ± 0.05, 7.31 ± 0.02 and 7.71 ± 0.04 (mean ± s.e.mean, n = 5). Ionomycin (1.2 μm) increased [Ca2+1 by 97.1 ± 17.6, 191.9 ± 48.7 and 322.8 ± 55.7 nm at the different values of pH1 respectively; TXB2 production was 0.7 ± 0.2, 2.1 ± 0.4 and 10.7 ± 3.3 ngjig−1 protein, and 12‐HETE production was 150.9 ± 68.2, 184.4 ± 77.9 and 302.3 ± 62.8 ng μg−1 protein.
Ammonium chloride (50 μm) caused a small reduction in pHo while increasing pHi from 7.32 ± 0.04 to 7.89 ± 0.05 and increasing ionomycin (1.2μm)‐induced [Ca2+]4 responses from 94.1 ± 67.3 to 721.6 ± 288.3 nm. TXB2 production increased from 3.1 ± 2.1 to 17.3 ± 8.2 and 12‐HETE production increased from 100.5 ± 26.7 to 203.2 ± 36.4 ngμg−1 protein. Responses of [Ca2+]i and TXB2 production to epoxymethano prostaglandin H2 (U46619, an endoperoxide‐thromboxane receptor agonist) increased significantly in the presence of NH4Cl.
Alterations of pH1 (such as may occur under pathological conditions) influence [Ca2+]i responses and eicosanoid synthesis in human platelets.
The role of bradykinin B1 receptors in the maintenance of intra‐articular plasma extravasation in chronic antigen‐induced arthritis
Authors: Cruwys S.C. , Garrett N.E. , Perkins M.N. , Blake D.R. , Kidd B.L. 
Published: July 2012

The role of bradykinin B1 and B2 receptors in bradykinin‐ and des‐Arg9‐bradykinin‐induced plasma extravasation in normal and inflamed rat knee joints was investigated by use of an antigen‐induced model of chronic arthritis. A modification of an Evans blue extraction technique allowed the unstimulated (basal) plasma extravasation to be assessed in this model. The contributions of bradykinin B1 and B2 receptors towards basal synovial plasma extravasation were determined.
In normal knees, intra‐articular injection of bradykinin (BK) induced plasma extravasation in a potent, dose‐dependent manner with a threshold of 0.01 nmol and an ED50 of 0.1 nmol. In day 5 arthritic knees, basal plasma extravasation was substantially enhanced. Lower doses of BK had no demonstrable effect and increases above basal extravasation were first observed at 0.1 nmol. Thereafter the dose‐response mirrored the response in normal knees and the maximal response was unaltered.
The B1 agonist, des‐Arg9‐BK, induced slight but significant plasma extravasation in normal knees but was less potent than bradykinin. This response was inhibited by the Bi receptor antagonist, des‐Arg9, [Leu8]‐BK. Lower doses of des‐Arg9‐BK bradykinin did not significantly increase basal extravasation in day 5 arthritic knees but, in contrast to BK, the maximal response was significantly enhanced.
The B2 antagonist, Hoe 140, inhibited BK‐induced plasma extravasation in normal joints over a dose‐range of 0.1‐1.0 nmol but was relatively inactive in day 5 inflamed knees. The B1 receptor antagonist, des‐Arg9, [Leu8]‐BK, was relatively inactive in normal joints but showed increased potency against BK‐induced plasma extravasation in day 5 arthritic joints.
Hoe 140 and des‐Arg9, [Leu8]‐BK both inhibited basal extravasation in arthritic joints on days 1 and 5 post‐challenge in a dose‐dependent fashion. Whilst Hoe 140 was the more potent inhibitor on day 1, it was less potent than des‐Arg9, [Leu8]‐BK on day 5.
Although the majority of responses to BK in normal tissue are mediated via B2 receptors, a small population of B1 receptors may exist in normal joint tissues. The data presented in this study suggest an evolving role for Bx receptors in the mediation of plasma extravasation in inflamed joint tissues. A role for BK antagonists in the treatment of arthritis is also suggested.
Pharmacological profile of the ATP‐mediated increase in L‐type calcium current amplitude and activation of a non‐specific cationic current in rat ventricular cells
Authors: Scamps Frédérique , Vassort Guy 
Published: July 2012

The pharmacological profile of the ATP‐induced increase in ICa amplitude and of ATP activation of a non‐specific cationic current, IATP, was investigated in rat ventricular cells.
The EC50 values for ICa increase and IATP activation were 0.36 μm and 0.76 μm respectively. Suramin (10 μm) and cibacron blue (1 μm) competitively antagonized both effects of ATP.
The rank order of efficacy and potency of ATP analogues in increasing ICa amplitude was 2‐methylthio‐ATP ≅ ATP ≅ ATPγS. The derivatives α,β‐methylene‐ATP, β,γ‐methylene‐ATP and β,γ‐imido‐ATP up to 500 μm had no significant effects.
The rank order of efficacy of ATP analogues in activating a non‐specific cationic current, IATP, was 2‐methylthio‐ATP > ATP > > ATPγS. The rank order of potency was 2‐methylthio‐ATP ≅ ATP. The EC50 of ATPγS could not be determined owing to its very low efficacy.
The ATP analogues α,β‐methylene‐ATP, β,γ‐methylene‐ATP and β,γ‐imido‐ATP at 500 μm did not activate IATP but acted as antagonists of activation of IATP by ATP.
The results suggest that the increase in ICa amplitude induced by external ATP is due to activation of P2Y‐purinoceptors.
The mechanism of IATP activation remains to be determined before the receptor subtype involved can be deduced.
Vasoconstrictor and vasodilator responses to various agonists in the rat perfused mesenteric arterial bed: selective inhibition by PPADS of contractions mediated via P2x‐purinoceptors
Authors: Windscheif Ursula , Ralevic Vera , Bäumert Hans G. , Mutschler Ernst , Lambrecht Günter , Burnstock Geoffrey 
Published: July 2012

The effect of pyridoxalphosphate‐6‐azophenyl‐2′,4′‐disulphonic acid (PPADS) on vasoconstrictor and/or vasodilator responses to various agonists and electrical field stimulation was investigated in the rat mesenteric arterial bed at basal tone and at tone raised by methoxamine (15–50 μm).
At basal tone, nucleotides produced vasoconstriction with the following rank order of potency: α,β‐methylene ATP > > 2‐methylthio ATP ≥ ATP = UTP. PPADS (0.3–10 μm) concentration‐dependently antagonized α,β‐methylene ATP‐, 2‐methylthio ATP‐ and ATP‐induced responses. UTP‐, noradrenaline‐ and nerve‐mediated (4–32 Hz) increases in perfusion pressure remained unaffected by 10 μm PPADS.
In raised tone preparations, nucleotides produced vasodilations, their rank order of potency being 2‐methylthio ATP > ATP > UTP. Responses to 2‐methylthio ATP were slightly antagonized, whereas ATP‐ and UTP‐induced responses remained unaffected by 10μm PPADS. In addition, acetylcholine‐and adenosine‐elicited relaxations were not influenced by 10 μm PPADS.
The present results confirm the previously described selective P2x antagonism by PPADS, this compound being ineffective at muscarinic M3‐ and adenosine P1‐receptors as well as at α1‐adrenoceptors. There was some inhibition of P2y‐purinoceptors but at a much higher concentration than required for inhibition of P2x‐purinoceptors.
In addition, this study provides evidence for the ineffectiveness of PPADS at both vasoconstriction‐and vasodilatation‐mediating P2u‐purinoceptors.
Haemodynamic actions of a novel sino‐atrial node function modulator, ZENECA ZD7288, in the anaesthetized dog: a comparison with zatebradine, atenolol and nitrendipine
Authors: Rouse W. , Johnson I.R. 
Published: July 2012

ZENECA ZD7288 (4‐(N‐ethyl‐N‐phenylamino)‐1,2‐dimethyl‐6‐(methylamino) pyrimidinium chloride, formerly ICI D7288) is a novel sino‐atrial node function modulator which selectively slows sinus node rate. Its effects on haemodynamic function have been studied in pentobarbitone anaesthetized dogs, in comparison with zatebradine, atenolol and nitrendipine.
ZD7288 lowered heart rate in the dose‐range 0.02 to 1.0 mg kg−1 i.v. from 152 to 77 beats min−1. Myocardial contractile function (measured as both dPLV/dtmax and right ventricular free wall developed force) decreased along with rate. Stroke volume increased as rate decreased. Cardiac output decreased at doses in excess of 0.2 mg kg−1, i.v.
These haemodynamic changes were reversed when heart rate reduction was reversed by atrial pacing and are, therefore, considered to be indirect consequences of heart rate changes induced by ZD7288.
The effects of zatebradine paralleled those of ZD7288 (heart rate reduced from 149 to 60.5 beats min−1 over the dose‐range 0.02 to 1.0 mg kg−1, i.v.), except that dPLV/dtmax did not decrease with heart rate and increased during arial pacing.
Neither ZD7288 nor zatebradine had significant effects on atrio‐ventricular conduction at intrinsic heart rates, but both significantly and dose‐dependently prolonged the atrio‐ventricular conduction interval during atrial pacing at 180 beats min−1.
The observed effects of atenolol were commensurate with removal of p‐sympathetic cardiac drive. Atrial pacing was found not to restore the pre‐atenolol haemodynamic state completely.
Nitrendipine up to 0.2 mg kg−1 i.v. induced changes indicative of direct vasodilatation accompanied by reflex compensation, followed by cardiac depression at higher doses. Atrial pacing failed to compensate for the effects of vasodilatation, but caused atrio‐ventricular conduction block at doses above O.S mg kg−1, i.v.
The data show ZD7288 has marked heart rate slowing properties and that accompanying haemodynamic changes appear to be secondary to the rate changes, being reversed by atrial pacing even in the continued presence of the drug. Heart rate slowing without depression of contractile function should prove to be of benefit in the treatment of myocardial ischaemia, particularly in the presence of myocardial dysfunction.
Pharmacological reactivity of human epicardial coronary arteries: phasic and tonic responses to vasoconstrictor agents differentiated by nifedipine
Authors: Stork Andrew P. , Cocks Thomas M. 
Published: July 2012

Human epicardial coronary artery rings, freshly obtained from cardiac transplantation patients, commonly exhibited phasic contractile activity in vitro. This activity occurred either spontaneously or in response to vasoconstrictor stimulation.
Nifedipine pretreatment (1 nm‐0.1 μm) reduced both types of phasic contractions in a concentration‐dependent manner. At 0.1 μm nifedipine, spontaneous contractions were completely abolished, as were phasic contractions induced by U46619, endothelin‐1 or 5‐hydroxytryptamine (5‐HT).
For U46619 (0.1–100 nm), the largest phasic contractions (amplitude peak to trough) occurred over the mid‐range of concentrations used (1–10 nm). At higher concentrations (30–100 nm), phasic activity was reduced as the response reached a maximum. Estimated pEC50 values for the upper phasic and lower phasic curves were significantly different (8.71 ± 0.13 versus 7.90 ± 0.11; P < 0.05; n = 10). In the presence of nifedipine (0.1 μm), the purely tonic contraction curve to U46619 was similar to the lower phasic curve in the absence of nifedipine (pEC50 = 8.14 ± 0.06, n = 10). Similar results were obtained for endothelin‐1 (0.1 −100 nm).
Responses to 5‐HT (1 nm‐3 μm) were more variable. The largest phasic contractions were spread unevenly throughout the concentration‐response curve. In the presence of nifedipine (0.1 μm), the curve to 5‐HT was significantly depressed in range but not sensitivity (pEC50) when compared with the phasic curves.
In conclusion, activation of dihydropyridine‐sensitive voltage‐operated Ca2+ channels mediated the phasic contractions commonly observed in human epicardial coronary arteries. These contractions amplified the contractile responses to low concentrations of vasoconstrictors. Inhibition of phasic activity by the Ca2+ channel antagonist, nifedipine, allowed the tonic vasoconstrictor profile of human isolated coronary artery to be determined which is important information for the accurate quantitative assessment of vasodilator responses in this tissue in vitro.
Effects of tenoxicam and aspirin on the metabolism of proteoglycans and hyaluronan in normal and osteoarthritic human articular cartilage
Authors: Manicourt Daniel Henri , Egeren Anne Druetz‐Van , Haazen Ludo , de Deuxchaisnes Charles Nagant 
Published: July 2012

As nonsteroidal antiinflammatory drugs may impair the ability of the chondrocyte to repair its damaged extracellular matrix, we explored the changes in the metabolism of newly synthesized proteoglycan (PG) and hyaluronan (HA) molecules produced by tenoxicam and aspirin in human normal cartilage explants and in osteoarthritic (OA) cartilage from age‐matched donors.
Explants were sampled from the medial femoral condyle and were classified by use of Mankin's histological‐histochemical grading system. Cartilage specimens were normal in 10 subjects, exhibited moderate OA (MOA) in 10 and had severe OA (SOA) in 10.
Cartilage explants were pulsed with [3H]‐glucosamine and chased in the absence and in the presence of either aspirin (190 μg ml1) or tenoxicam (4–16 μg ml−1). After papain digestion, the labelled chondroitin sulphate ([3H]‐PGs) and HA([3H]‐HA) molecules present in the tissue and media were purified by anion‐exchange chromatography.
In normal cartilage as well as in explants with MOA and SOA aspirin reduced more strongly PG and HA synthesis than the loss of [3H]‐HA and [3H]‐PGs.
In normal cartilage, tenoxicam did not affect PG metabolism whereas it reduced HA synthesis in a dose‐dependent manner and did not change or even increased the net loss of [3H]‐HA. In contrast, in OA cartilage, tenoxicam produced a stronger reduction in the loss of [3H]‐PGs than in PG synthesis and this decrease occurred at lower concentrations in cartilage with SOA (4–8 μg ml−1) than in cartilage with MOA (8–16 μg ml−1). In cartilage with MOA, the metabolic balance of HA was unaffected by tenoxicam whereas in cartilage with SOA, the drug decreased the loss of [3H]‐HA and concomitantly did not change or even increased HA synthesis.
The data obtained in short‐term in vitro cultures indicate that aspirin may produce OA‐like changes in normal cartilage and is likely to worsen the disease process in OA tissue. On the other hand, although tenoxicam may reduce the HA content of normal cartilage, and, in so doing, may produce OA‐like lesions, this drug should not per se accelerate joint failure in OA.
Prevention of thrombosis and rethrombosis and enhancement of the thrombolytic actions of recombinant tissue‐type plasminogen activator in the canine heart by DMP728, a glycoprotein IIb/IIIa antagonist
Authors: Lucchessi Benedict R. , Rote William E. , Driscoll Edward M. , Mu Dun‐Xue 
Published: July 2012

We studied DMP728, a non‐peptide glycoprotein (GP) IIb/IIIa receptor antagonist, for prevention of coronary artery thrombosis or rethrombosis in a chronic canine model subjected to arterial injury.
In protocol I, DMP728 (1.0 mg kg−1, i.v., n = 8) or saline (n = 8) was administered and a 150 μA anodal current was applied to the intimal surface of the left circumflex coronary artery (LCX). Dogs were monitored for 6 h and again on each of 5 subsequent days.
Ex vivo platelet aggregation was inhibited but returned to baseline 1 day after drug administration. Thrombus weight was reduced (saline, 20.7 ± 5.0 mg; DMP728 1.7 ± 0.4mg; P < 0.05), as was infarct size [saline, 27.5 ± 4.3; DMP728, 1.6 ± 0.7 (per cent left ventricle); P < 0.05]. All control animals died by day 3, while all but one of the treated dogs survived the entire protocol (P < 0.05).
In protocol II, an LCX thrombus was induced and thrombolytic therapy was initiated 30 min later. DMP728 (1.0 mg kg−1, i.v., n = 8) or saline (n = 8) was administered 5 min after recombinant tissue‐type plasminogen activator infusion had begun. The incidence of reocclusion was reduced by DMP728 (saline, 4/8; DMP728, 1/8). One day after thrombolysis, 7/8 DMP728‐treated animals were alive compared with 1/8 in the control group (P = 0.01).
DMP728 inhibited ex vivo platelet aggregation, prevented primary and secondary occlusive thrombus formation, reduced thrombus weight and infarct size and increased survival in a chronic canine model of coronary artery thrombus formation. DMP728 is an effective anti‐platelet intervention when used as the singular adjunctive agent in association with thrombolytic therapy.
Regional effects of amphetamine, cocaine, nomifensine and GBR 12909 on the dynamics of dopamine release and metabolism in the rat brain
Authors: Karoum Tarouk , Chrapusta Stanislaw J. , Brinjak Raymond , Hitri Ana , Wyatt Richard J. 
Published: July 2012

The effects of single‐dose regimens of amphetamine, cocaine, nomifensine and GBR 12909 on the dynamics of dopamine (DA) release and metabolism were evaluated in the frontal cortex, hypothalamus, nucleus accumbens and striatum. The regimens selected are known to produce substantial behavioural effects.
3‐Methoxytyramine (3MT) and 3,4‐dihydroxyphenylacetic acid (DOPAC) rates of formation were used to assess DA metabolism by catechol‐O‐methyltransferase and monoamine oxidase respectively. The rate of formation of 3MT was used as an index of synaptic DA. The ratio and sum, respectively, of 3MT and DOPAC rates of formation were used to assess DA reuptake inhibition and turnover.
The effects of amphetamine on 3MT production and DOPAC steady‐state levels were similar in all regions, suggesting similar pharmacodynamic actions. Amphetamine increased 3MT formation and steady‐state levels, and reduced DOPAC steady‐state levels. DOPAC formation was significantly reduced only in the nucleus accumbens and striatum. Total DA turnover remained unchanged except in the nucleus accumbens. Apparently, the amphetamine‐induced increase in DA release occurred at the expense of intraneuronal DA metabolism and did not require stimulation of synthesis.
Nomifensine elevated 3MT formation in all regions. A similar effect was produced by cocaine except in the nucleus accumbens. GBR 12909 elevated 3MT production only in the hypothalamus, the striatum and the nucleus accumbens.
Cocaine selectively reduced DOPAC formation in the frontal cortex. Nomifensine increased and reduced, respectively, DOPAC formation in striatum and hypothalamus. GBR 12909 elevated DOPAC formation in all regions except the cortex, where pargyline did not reduce DOPAC levels in GBR 12909‐treated rats.
Ratios and sum of 3MT and DOPAC rates of formation also exhibited wide regional variations for each drug. In contrast to the other drugs, the ratio was not increased after GBR 12909. Apparently, the DA uptake properties of this drug are poorly related to its in vivo effects on the ratio of 3MT production to that of DOPAC, which should increase when DA reuptake is inhibited.
Total DA turnover was increased by GBR 12909 in the hypothalamus, nucleus accumbens and striatum, while cocaine and nomifensine increased it only in the nucleus accumbens and striatum respectively.
It is concluded that:

3MT and DOPAC rates of formation provide better indices of DA release and metabolism than do their steady‐state concentrations.
Some effects of DA uptake blockers on DA transmission, especially those of nomifensine and cocaine, may be attributed to increased DA release.
Patterns of regional effects of psychostimulants on the dynamics of DA release and metabolism may be better biochemical correlates of stimulant‐induced behaviours than would changes in any single region.
Pharmacological analysis of ecto‐ATPase inhibition: evidence for combined enzyme inhibition and receptor antagonism in P2X‐purinoceptor ligands
Authors: Crack B.E. , Beukers M.W. , McKechnie K.C.W. , IJzerman A.P. , Leff P. 
Published: July 2012

Previous studies have shown that suramin and FPL 66301 are competitive antagonists at the P2X‐purinoceptor in the rabbit ear artery. Those studies employed α,β‐methylene ATP, a poorly hydrolysable ATP analogue, as the agonist. In this study these compounds have been tested using ATP as the agonist.
Suramin, in the concentration range 30–1000 μm, potentiated the contractile effects of ATP, producing a 3‐fold leftward shift of the ATP E/[A] curves. FPL 66301, in the concentration range 100–1000 μm, produced a significant but small (3‐fold) rightward shift of the ATP curves. These results are in marked contrast with previous studies using α,β‐methylene ATP in which 30‐fold rightward shifts were achieved using the same concentration ranges of suramin and FPL 66301.
Suramin and FPL 66301 were tested as ecto‐ATPase inhibitors in a human blood cell assay. Suramin inhibited the enzyme with a pIC50 of 4.3, FPL 66301 with a pIC50 of 3.3.
The pharmacological data were analysed using a theoretical model describing the action of a compound with dual enzyme inhibitory and receptor antagonistic properties on the effects of an agonist susceptible to enzymatic degradation. The model was found to fit the data well using the known pKBestimates for suramin and FPL 66301 and similar relative (but not absolute) pK1 estimates to those obtained for the compounds in the enzyme assay.
From this analysis it was concluded that the limited shifts of ATP E/[A] curves produced by suramin and FPL 66301 were the result of ‘self‐cancellation’ of the potentiating (enzyme inhibitory) and rightward‐shifting (receptor antagonistic) properties.
The analysis also indicated that the presence of ecto‐ATPase activity in the rabbit ear artery preparation has a marked effect on the apparent potency of ATP. The experimental p[A50] was 3.4, whereas the ‘true’ value, that is the value which would be obtained in the absence of ecto‐ATPase activity, was 6.0, some 400‐fold higher.
Two conclusions are drawn from this study. Firstly, caution must be exercised in the use of suramin and FPL 66301 as tools for receptor classification. Absence of overt antagonism by these compounds when metabolically unstable agonists are used could lead to erroneous claims for receptor subtypes. Secondly, the agonist potency order currently used to designate P2X‐ purinoceptors may require modification.