bluuebunny/crossref_metadata_2025_split huggingface dataset:
Discrimination between citrulline and arginine transport in activated murine macrophages: inefficient synthesis of NO from recycling of citrulline to arginine
Authors: Baydoun Anwar R. , Bogle Richard G. , Pearson Jeremy D. , Mann Giovanni E. 
Published: July 2012

The kinetics, specificity, pH‐ and Na+‐dependency of l‐citrulline transport were examined in unstimulated and lipopolysaccharide (LPS)‐activated murine macrophage J774 cells. The dependency of nitric oxide production on extracellular arginine or citrulline was investigated in cells activated with LPS (1 μg ml−1) for 24 h.
In unstimulated J774 cells, transport of citrulline was saturable (Kt = 0.16 mm and Vmax = 32 pmol μg−1 protein min−1), pH‐insensitive and partially Na+‐dependent. In contrast to arginine, transport of citrulline was unchanged in LPS‐activated (1 μg ml−1, 24 h) cells.
Kinetic inhibition experiments revealed that arginine was a relatively poor inhibitor of citrulline transport, whilst citrulline was a more potent inhibitor (Ki = 3.4 mm) of arginine transport but only in the presence of extracellular Na+. Neutral amino acids inhibited citrulline transport (Ki = 0.2–0.3 mm), but were poor inhibitors of arginine transport.
Activated J774 cells did not release nitrite in the absence of exogenous arginine. Addition of citrulline (0.01 − 10 mm), in the absence of exogenous arginine, could only partially restore the ability of cells to synthesize nitrite, which was abolished by 100 μm NG‐nitro‐l‐arginine methyl ester or NG‐iminoethyl‐l‐ornithine.
Intracellular metabolism of l‐[14C]‐citrulline to l‐[14C]‐arginine was detected in unstimulated J774 cells and was increased further in cells activated with LPS and interferon‐γ.
We conclude that J774 macrophage cells transport citrulline via a saturable but nonselective neutral carrier which is insensitive to induction by LPS. In contrast, transport of arginine via the cationic amino acid system y+ is induced in J774 cells activated with LPS.
Our findings also confirm that citrulline can be recycled to arginine in activated J774 macrophage cells. Although this pathway provides a mechanism for enhanced arginine generation required for NO production under conditions of limited arginine availability, it cannot sustain maximal rates of NO synthesis.
Effect of salmeterol on human nasal epithelial cell ciliary beating: inhibition of the ciliotoxin, pyocyanin
Authors: Kanthakumar K. , Cundell D.R. , Johnson M. , Wills P.J. , Taylor G.W. , Cole P.J. , Wilson R. 
Published: July 2012

Patients with airway infection by Pseudomonas aeruginosa have impaired mucociliary clearance. Pyocyanin is a phenazine pigment produced by P. aeruginosa which is present in the sputum of colonized patients, slows human ciliary beat frequency (CBF) in vitro and slows mucociliary transport in vivo in the guinea‐pig.
We have investigated the effect of salmeterol, a long‐acting β2‐adrenoceptor agonist, on pyocyanin‐induced slowing of human CBF in vitro. Salmeterol (2 × 10−7 m) was found to reduce pyocycanin (20 μg ml−1)‐induced slowing of CBF by 53% and the fall in intracellular adenosine 3′:5′‐cyclic monophosphate (cyclic AMP) by 26% and ATP by 29%.
Another β2‐adrenoceptor agonist, isoprenaline (2 × 10−7 m), also inhibited pyocyanin‐induced slowing of CBF by 39%.
The effects of salmeterol (30 min preincubation) persisted after washing the cells.
Propranolol (10−7 m) and the β2‐specific antagonist, ICI 118551 (10−6 m) blocked the protective effects of salmeterol completely, but atenolol (10−6 m) was less effective. These results suggested that the effects of salmeterol on pyocyanin‐induced effects were mediated primarily via the stimulation of β2‐adrenoceptors.
Pyocyanin‐induced ciliary slowing is associated with a substantial fall in intracellular cyclic AMP and ATP. Salmeterol reversed the effects of pyocyanin on cyclic AMP and ATP.
Mucociliary clearance is an important defence mechanism of the airways against bacterial infection. Salmeterol may benefit patients colonized by P. aeruginosa, not only by its bronchodilator action, but also by protecting epithelial cells from pyocyanin‐induced slowing of CBF.
Recovery after dietary vitamin E supplementation of impaired endothelial function in vitamin E‐deficient rats
Authors: Rubino Annalisa , Burnstock Geoffrey 
Published: July 2012

Thoracic aortae, isolated from rats supplemented with dietary vitamin E after vitamin E deficiency, were analysed for changes in vascular reactivity.
Following 4 or 12 months of dietary vitamin E deficiency, endothelium‐dependent vasodilator responses to acetylcholine were significantly impaired. However, when animals were fed after the first 4 months of vitamin E deprivation with a vitamin E‐supplemented diet for 8 months, endothelium‐mediated responses were completely restored.
In contrast, the endothelium‐independent vasodilator or vasoconstrictor responses to sodium nitroprusside and noradrenaline, respectively were not altered either by vitamin E deficiency or supplementation.
These data indicate that vitamin E supplementation reversed the impairment of endothelial cell function which occurs during vitamin E deficiency.
Competitive and non‐competitive effects of 5‐hydroxyindole on 5‐HT3 receptors in N1E‐115 neuroblastoma cells
Authors: Kooyman André R. , van Hooft Johannes A. , Vanderheijden Patrick M.L. , Vijverberg Henk P.M. 
Published: July 2012

Effects of 5‐hydroxyindole (5‐OH‐indole) (the aromatic moiety of 5‐hydroxytryptamine (5‐HT)) on 5‐HT‐evoked ion current and the nature of these effects on 5‐HT3 receptors have been investigated in whole‐cell voltage clamp and radioligand binding experiments on cultured N1E‐115 mouse neuroblastoma cells.
The amplitude of 10 μm 5‐HT‐evoked ion currents was enhanced up to 150% of the control value by increasing concentrations up to 10 mm 5‐OH‐indole with half maximum effect of 0.8 mm. At concentrations between 10 mm and 50 mm, 5‐OH‐indole blocked the 5‐HT‐evoked ion current. Both the enhancement and the block by 5‐OH‐indole were accompanied by a marked slowing of the kinetics of decay of the 5‐HT‐evoked inward currents.
The blocking effect was surmounted when the 5‐HT concentration was raised from 10 μm to 100 μm. Conversely, the increase in amplitude and the slowing of the decay of the 5‐HT‐evoked ion current induced by 1 mm 5‐OH‐indole were not reversed by the same increase of 5‐HT concentration.
The binding of the selective antagonist [3H]‐GR65630 to 5‐HT3 receptors was displaced by 5‐OH‐indole in a concentration‐dependent manner with a pKi of 1.96. In saturation binding experiments 10 mm 5‐OH‐indole reduced the affinity of [3H]‐GR65630, whereas the total number of binding sites remained unaffected.
It is concluded that the blocking effect of high concentrations of 5‐OH‐indole is due to a competitive interaction with the antagonist recognition sites of 5‐HT3 receptors, whereas the potentiating effect of lower concentrations of 5‐OH‐indole appears to be mediated by a distinct non‐competitive interaction.
Evidence for differential roles of nitric oxide (NO) and hyperpolarization in endothelium‐dependent relaxation of pig isolated coronary artery
Authors: Kilpatrick E.V. , Cocks T.M. 
Published: July 2012

The possible roles of endothelial and smooth muscle cell hyperpolarization and nitric oxide (NO) in endothelium‐dependent relaxation were examined in isolated rings of pig right coronary artery.
The effects of hyperpolarization were prevented with high K+ (30–125 mm), isotonic Krebs solutions. Functional antagonism due to high K+‐induced smooth muscle contraction was prevented with 0.3 μm nifedipine (in all treatments, for consistency). All rings were contracted with the thromboxane‐mimetic U46619, (1 − 100 nm) to bring them to an initial active force of within 30–50% of maximum contraction.
High K+ had no effects on the sensitivity (EC50) or time course of endothelium‐dependent (substance P, SP; bradykinin, BK; calcimycin, A23187) and ‐independent (sodium nitroprusside, SNP) agents. Maximum relaxations (Rmax) to SP, BK and A23187 were reduced significantly by approximately 20% but only with 125 mm K+.
In normal K+ Krebs solution (5.9 mm), NG‐nitro‐l‐arginine (l‐NOARG; 100 μm) caused 40%, 20% and no reduction in Rmax for SP, BK and SNP respectively. EC50s for SP and BK were decreased significantly by approximately two fold whereas that for SNP was increased significantly by approximately ten fold. At all high K+ concentrations (30–125 mm), l‐NOARG (100 μm) caused complete inhibition of relaxations to SP and BK but those to SNP were unaffected.
High K+ (30 mm) unmasked potent and concentration‐dependent inhibition of relaxations of SP by l‐NOARG. At 10 μm l‐NOARG, all relaxation responses to SP were abolished and at the higher concentrations of SP (1 − 10 nm) small but significant contractions were observed.
NG‐monomethyl‐l‐arginine (l‐NMMA) had similar effects on relaxations to SP in the presence of 30 mm K+ except that maximum inhibition (40%) of Rmax was achieved at 10 μm l‐NMMA and this was not increased with either 100 or 1000 μm l‐NMMA. In normal K+, l‐NMMA (1000 μm) only decreased the EC50 by approximately two fold, without affecting Rmax.
High choline+ (25, 75 and 125 mm) isotonic Krebs also had no direct effect on the relaxations to SP, but like high K+, enabled l‐NOARG (100 μm) to inhibit these responses completely. Neither charyb‐dotoxin (30 nm) nor substitution of 25 mm NaCl with 50 mm sucrose had any direct effect on relaxations to SP or on the block of relaxations to SP by l‐NOARG (100 μm).
In conclusion, most if not all of the endothelium‐dependent relaxation in the pig coronary artery in vitro is due to NO, but hyperpolarization can supplement 60%–80% of this response if NO synthesis is blocked. Multiple endothelium‐derived factors could not only explain heterogeneity of the degree of block of endothelium‐dependent relaxation responses by l‐arginine analogues, but also constitute important ‘back‐up’ mechanisms for control of arterial diameter.
Stimulation by menthol of Cl secretion via a Ca2+‐dependent mechanism in canine airway epithelium
Authors: Chiyotani A. , Tamaoki J. , Takeuchi S. , Kondo M. , Isono K. , Konno K. 
Published: July 2012

To investigate the effect of menthol on airway epithelial ion transport function, we studied the bioelectrical properties of canine cultured tracheal epithelium by Ussing's short‐circuit technique in vitro.
Addition of menthol (10−3 m) to the mucosal but not the submucosal solution increased the short‐circuit current (Isc) from 6.2 ± 0.9 to 14.0 ± 2.2 μA cm−2 (P < 0.001), and this effect was accompanied by increases in transepithelial potential difference and conductance. The response was dose‐dependent, with the maximal increase from the baseline value and the concentration required to produce a half‐maximal effect (EC50) being 6.4 ± 0.9 μA cm−2 (P < 0.001) and 40 μm, respectively.
Other cyclic alcohols, including menthone and cyclohexanol, had no effect on the electrical properties.
The menthol‐induced increase in Isc was not altered by pretreatment of the cells with amiloride, indomethacin, or propranolol but was abolished by diphenylamine‐2‐carboxylate, furosemide or substitution of Cl with iodide in the medium.
Menthol (10−2 m) increased cytosolic levels of free calcium ([Ca2+]i) from 98 ± 12 to 340 ± 49 nm (P < 0.01) in fura‐2‐loaded tracheal epithelium but did not affect the intracellular adenosine 3′,5′‐cyclic monophosphate content.
These results suggest that menthol stimulates Cl secretion across airway epithelium, probably through a Ca2+‐dependent mechanism, and might thus influence mucociliary transport in the respiratory tract.
Cell inward transport of l‐DOPA and 3‐O‐methyl‐l‐DOPA in rat renal tubules
Authors: Soares‐da‐Silva P. , Fernandes M.H. , Pinto‐do‐OA P.C. 
Published: July 2012

The present study has determined the kinetics of the uptake of l‐3,4‐dihydroxyphenylalanine (l‐DOPA) and 3‐O‐methyl‐l‐DOPA (3‐OMDOPA) in rat renal tubules and examined the effect of 3‐OMDOPA on the inward transport of l‐DOPA and on its conversion into dopamine in kidney homogenates.
The accumulation of both l‐DOPA and 3‐OMDOPA in renal tubules was found to occur through non‐saturable and saturable mechanisms. The kinetics of the saturable component of l‐DOPA and 3‐OMDOPA uptake in renal tubules were as follows: l‐DOPA, Vmax = 11.1 nmol mg−1 protein h−1 and Km = 216 μm (n = 6); 3‐OMDOPA, Vmax = 8.1 nmol mg−1 protein h−1 and Km = 231 μm (n = 5). The diffusion constant of the non‐saturable component for the accumulation of l‐DOPA and 3‐OMDOPA was 0.0010 and 0.0014 μmol−1, respectively.
3‐OMDOPA (100 to 2000 μm) was found to produce a concentration‐dependent decrease (29% to 81% reduction) of the saturable component of the tubular uptake of l‐DOPA; the Ki value of 3‐OMDOPA for inhibition of l‐DOPA uptake was found to be 181 μm (n = 5). The accumulation of l‐DOPA obtained in experiments conducted at 4°C was not affected by 3‐OMDOPA.
In experiments conducted in kidney homogenates only l‐DOPA (10 to 5000 μm) was found to be decarboxylated. The Vmax and Km values for aromatic l‐amino acid decarboxylase determined in the absence of 3‐OMDOPA (Vmax = 14.1 nmol mg−1 protein h−1; Km = 62 μm) were not significantly different from those observed when the decarboxylation of l‐DOPA was carried out in the presence of 1000 μm 3‐OMDOPA (Vmax = 15.7 nmol mg−1 protein h−1; Km = 68 μm).
It is concluded that the tubular uptake of both l‐DOPA and 3‐OMDOPA occur through non‐saturable and saturable mechanisms; only the saturable tubular uptake of l‐DOPA was found to be inhibited by 3‐OMDOPA. It is further shown that 3‐OMDOPA neither undergoes decarboxylation into 3‐MT nor affects the decarboxylation of l‐DOPA.
Improvement of cardiovascular effects of metoprolol by replacement of common salt with a potassium‐ and magnesium‐enriched salt alternative
Authors: Mervaala Eero M.A. , Laakso Juha , Vapaatalo Heikki , Karppanen Heikki 
Published: July 2012

The influence of sodium chloride (NaCl)‐enrichment of the diet (6% of the dry weight) and that of a novel sodium‐reduced, potassium‐, magnesium‐, and l‐lysine‐enriched salt alternative on the cardiovascular effects of the β1‐adrenoceptor blocking drug, metoprolol, was studied in stroke‐prone spontaneously hypertensive rats.
Increased dietary sodium chloride intake produced a marked rise in blood pressure and induced left ventricular and renal hypertrophy. By contrast, the salt alternative did not increase blood pressure and caused remarkably less cardiac and renal hypertrophy than did sodium chloride.
Metoprolol treatment at a daily dose of 250 mg kg−1 lowered blood pressure and decreased left ventricular hypertrophy index during the control diet. Sodium chloride‐enrichment blocked the antihypertensive effect of metoprolol, while a partial protective effect on left ventricular and renal hypertrophy persisted. In the presence of the salt alternative‐enrichment both at the level of 6% and 10.5% (corresponding to a NaCl level of 6%), metoprolol was fully able to exert its beneficial cardiovascular and renal effects.
Both salt supplementations, irrespective of metoprolol treatment, induced a 3 to 4 fold increase in the urinary excretion of calcium. There was a linear correlation between the urinary excretions of sodium and calcium. The urinary excretion of magnesium rose by 90% and that of potassium by 110% in the salt alternative group.
Our findings suggest that replacement of common salt by a potassium‐, and magnesium‐enriched salt alternative in the diet produces beneficial cardiovascular effects and improves the antihypertensive efficacy of metoprolol in stroke‐prone spontaneously hypertensive rats. Increased intake of potassium and/or magnesium and l‐lysine from the salt alternative is involved in the beneficial effects of the salt alternative. The NaCl‐induced myocardial and renal hypertrophies appear to be partially mediated by β‐adrenoceptor activation.
Evaluation of a series of novel CCKB antagonists using a functional assay in the rat central nervous system
Authors: Boden P.R. , Pinnock R.D. , Pritchard M.C. , Woodruff G.N. 
Published: July 2012

Electrophysiological recordings from rat ventromedial hypothalamus (VMH) in vitro have been used to compare the effects of novel chemical entities on CCKB receptor activation in the rat central nervous system.
Twenty compounds from three different chemical series were evaluated for their ability to reduce pentagastrin‐induced increases in action potential firing rate.
All twenty compounds studied were found to be CCKB antagonists, with equilibrium constants spanning a concentration‐range of several orders of magnitude. The rank order for their ability to block pentagastrin responses correlated well with values obtained for their relative affinities for the mouse cortex CCKB binding site.
It is concluded that the VMH preparation provides a good functional correlate to binding assays in the rodent central nervous system for a structurally diverse series of CCKB antagonists.
The effects of sigma ligands and of neuropeptide Y on N‐methyl‐d‐aspartate‐induced neuronal activation of CA3 dorsal hippocampus neurones are differentially affected by pertussin toxin
Authors: Monnet François P. , Debonnel Guy , Bergeron Richard , Gronier Benjamin , de Montigny Claude 
Published: July 2012

The in vivo effects of the high affinity sigma ligands 1,3‐di(2‐tolyl)guanidine (DTG), (+)‐N‐cyclopropylmethyl‐N‐methyl‐1,4‐diphenyl‐1‐ethyl‐but‐3‐en‐1‐ylamine hydrochloride (JO‐1784), (+)‐pentazocine and haloperidol, as well as of those of neuropeptide Y (NPY), on N‐methyl‐d‐aspartate (NMDA)‐ and quisqualate (Quis)‐induced neuronal activations of CA3 pyramidal neurones were assessed, using extracellular unitary recording, in control rats and in rats pretreated with a local injection of pertussis toxin (PTX), to evaluate the possible involvement of Gi/o proteins in mediating the potentiation of the neuronal response to NMDA by the activation of sigma receptors in the dorsal hippocampus.
Microiontophoretic applications as well as intravenous injections of (+)‐pentazocine potentiated selectively the NMDA response in control rats as well as in PTX‐pretreated animals. In contrast, the PTX pretreatment abolished the potentiation of the NMDA response by DTG, JO‐1784 and NPY. Moreover, microiontophoretic applications of DTG induced a reduction of NMDA‐induced neuronal activation. Neither in control nor in PTX‐treated rats, did the sigma ligands and NPY have any effect on Quis‐induced neuronal response.
In PTX‐treated rats, the potentiation of the NMDA response induced by (+)‐pentazocine was suppressed by haloperidol, whereas the reduction of the NMDA response by DTG was not affected by haloperidol.
This study provides the first in vivo functional evidence that sigma ligands and NPY modulate the NMDA response by acting on distinct receptors, differentiated by their PTX sensitivity.
Comparative studies on the affinities of ATP derivatives for P2X‐purinoceptors in rat urinary bladder
Authors: Bo Xuenong , Fischer Bilha , Maillard Michel , Jacobson Kenneth A. , Burnstock Geoffrey 
Published: July 2012

Radioligand binding assays have been used to determine the affinities of a series of ATP derivatives with modifications of the polyphosphate chain, adenine and ribose moieties of the ATP molecule for [3H]‐α,β‐methylene ATP ([3H]‐α,β‐MeATP) binding sites in rat urinary bladder.
The replacement of the bridging oxygen in the triphosphate chain of ATP (pIC50 = 5.58) with a methylene or imido group markedly increased the affinity (691 fold in IC50 values for β,γ‐imidoATP, 15 fold for β,γ‐methylene ATP), and the replacement of an ionized oxygen on the γ‐phosphate with a sulphur (ATPγS) also led to increased affinity (5623 fold in IC50 values).
Modifications at N6, N1, and C‐8 positions on the purine base usually reduced the affinity of ATP (a decrease of 2.8 fold in IC50 values for N6‐methylATP and 8.9 fold for 8‐bromo ATP), while the attachment of an alkylthio group to the C‐2 position greatly increased the affinity for P2X‐purinoceptors (from 3.5 to 98 fold increase in IC50 values).
Replacement of the 3′‐hydroxyl group on the ribose with substituted amino or acylamino groups produced more potent P2X‐purinoceptor agonists (an increase of 447 fold in IC50 values for 3′‐deoxy‐3′‐benzylamino ATP and 28 fold for 3′‐deoxy‐3′‐(4‐hydroxyphenylpropionyl)amino ATP.
Diadenosine polyphosphates (Ap[n]A) were also shown to displace the [3H]‐α,β‐MeATP binding. The rank order of potency was Ap6A > Ap5A > Ap4A >> Ap3A >> Ap2A.
Suramin, PPADS, and reactive blue 2 could competitively displace the binding of [3H]‐α,β‐MeATP to P2X‐purinoceptors, with pIC50 values of 6.26, 5.35, and 6.22, respectively.
Muscarinic acetylcholine response in pyramidal neurones of rat cerebral cortex
Authors: Nishikawa M. , Munakata M. , Akaike N. 
Published: July 2012

The effects of acetylcholine (ACh) on pyramidal neurones acutely dissociated from the rat cerebral cortex were studied in the whole‐cell mode, by use of the nystatin‐perforated patch recording configuration.
ACh induced a net inward current (IACh) accompanied by a membrane conductance decrease at a holding potential (VH) of − 40 mV. IACh increased in a concentration‐dependent manner with a half‐maximum concentration (EC50) of 8.7 × 10−7 M.
IACh mainly resulted from the suppression of the voltage‐ and time‐dependent K+ current (M‐current).
Muscarine and muscarinic agonists such as McN‐A‐343, oxotremorine and oxotremorine‐M mimicked the ACh response. The potency was in the order of oxotremorine‐M > McN‐A‐343 ≥ muscarine > oxotremorine.
Pirenzepine shifted the concentration‐response curve for ACh to the right and the corresponding Schild plot yielded a pA2 value of 7.81. Other muscarinic antagonists also reversibly blocked IACh in a concentration‐dependent manner. The inhibitory potency was in the order of atropine > 4‐DAMP > pirenzepine > AF‐DX‐116.
IACh could be induced normally even after pre‐incubation of dissociated neurones in external solution with 200 ng ml−1 pertussis toxin (PTX) for 8 h, whereas the inhibitory effect of ACh on high‐voltage‐activated Ca2+ channels was completely abolished by the PTX treatment.
Behavioural and neurochemical adaptations to nicotine in rats: influence of NMDA antagonists
Authors: Shoaib M. , Benwell M.E.M. , Akbar M.T. , Stolerman I.P. , Balfour D.J.K. 
Published: July 2012

The repeated co‐administration of the non‐competitive N‐methyl‐d‐aspartate (NMDA) receptor antagonist dizocilpine (0.1 and 0.3 mg kg−1, i.p.) with nicotine (0.4 mg kg−1, s.c.) attenuated the development of tolerance to the locomotor depressant effect of the nicotine in rats.
The repeated co‐administration of the competitive NMDA antagonist d‐CPPene (SDZ EAA 494; 3‐(2‐carboxypiperazin‐4‐yl)‐1‐propenyl‐1‐phosphonic acid, 2 and 8 mg kg−1, i.p.) also attenuated tolerance to the locomotor depressant effect of nicotine.
Dizocilpine (0.3 mg kg−1, i.p.) pretreatment attenuated sensitization to the locomotor stimulant effect of nicotine (0.4 mg kg−1, s.c.) and prevented sensitization of nicotine‐induced dopamine release in the nucleus accumbens. However, pretreatment with dizocilpine alone caused a modest enhancement of the behavioural response to a subsequent acute dose of nicotine.
d‐CPPene (2.0 mg kg−1, i.p.) pretreatment prevented sensitization to the nicotine‐induced dopamine release in the nucleus accumbens. There was no enhanced locomotor response that could be attributed to nicotine pretreatment when d‐CPPene was co‐administered with nicotine. However, pretreatment with d‐CPPene alone enhanced the locomotor response to an acute dose of nicotine.
The results suggest the involvement of NMDA receptors in adaptations of the behavioural and neurochemical effects of nicotine that occur as a result of repeated administration of the drug.