bluuebunny/crossref_metadata_2025_split huggingface dataset:
Inhibition of human platelet aggregation by a novel S‐nitrosothiol is abolished by haemoglobin and red blood cells in vitro: implications for anti‐thrombotic therapy
Authors: Megson Ian L , Sogo Naoki , Mazzei Francesca A , Butler Anthony R , Walton John C , Webb David J 
Published: January 2005

S‐Nitrosothiols are nitric oxide (NO) donor drugs that have been shown to inhibit platelet aggregation in platelet rich plasma (PRP) in vitro and to inhibit platelet activation in vivo. The aim of this study was to compare the platelet effects of a novel S‐nitrosated glyco‐amino acid, RIG200, with an established S‐nitrosothiol, S‐nitrosoglutathione (GSNO) in PRP, and to investigate the effects of cell‐free haemoglobin and red blood cells on S‐nitrosothiol‐mediated inhibition of platelet aggregation.
The effects of GSNO and RIG200 in collagen (2.5 μg ml−1)‐induced platelet aggregation in PRP and whole blood were investigated in vitro. Both compounds were found to be powerful inhibitors of aggregation in PRP, and RIG200 was significantly more potent (IC50=2.0 μM for GSNO and 0.8 μM for RIG200; P=0.04).
Neither compound inhibited aggregation in whole blood, even at concentrations of 100 μM. Red blood cell concentrations as low as 1% of the haematocrit, and cell‐free haemoglobin (2.5 μM), significantly reduced their inhibitory effects on platelets.
Experiments involving measurement of cyclic GMP levels, electrochemical detection of NO and electron paramagnetic resonance of haemoglobin in red blood cells, indicated that scavenging of NO generated from S‐nitrosothiols by haemoglobin was responsible for the lack of effect of S‐nitrosothiols on platelets in whole blood.
These studies suggest that scavenging of NO by haemoglobin in blood might limit the therapeutic application of S‐nitrosothiols as anti‐platelet agents.

British Journal of Pharmacology (2000) 131, 1391–1398; doi:10.1038/sj.bjp.0703731
Molecular impact of MinK on the enantiospecific block of IKs by chromanols
Authors: Lerche C , Seebohm G , Wagner C I , Scherer C R , Dehmelt L , Abitbol I , Gerlach U , Brendel J , Attali B , Busch A E 
Published: January 2005

Slowly activating IKs (KCNQ1/MinK) channels were expressed in Xenopous oocytes and their sensitivity to chromanols was compared to homomeric KCNQ1 channels. To elucidate the contribution of the β‐subunit MinK on chromanol block, a formerly described chromanol HMR 1556 and its enantiomer S5557 were tested for enantio‐specificity in blocking IKs and KCNQ1 as shown for the single enantiomers of chromanol 293B. Both enantiomers blocked homomeric KCNQ1 channels to a lesser extent than heteromeric IKs channels. Furthermore, we expressed both WT and mutant MinK subunits to examine the involvement of particular MinK protein regions in channel block by chromanols. Through a broad variety of MinK deletion and point mutants, we could not identify amino acids or regions where sensitivity was abolished or strikingly diminished (>2.5 fold). This could indicate that MinK does not directly take part in chromanol binding but acts allosterically to facilitate drug binding to the principal subunit KCNQ1.British Journal of Pharmacology (2000) 131, 1503–1506; doi:10.1038/sj.bjp.0703734
Thrombin causes endothelium‐dependent biphasic regulation of vascular tone in the porcine renal interlobar artery
Authors: Derkach Dmitry N , Ihara Eikichi , Hirano Katsuya , Nishimura Junji , Takahashi Shosuke , Kanaide Hideo 
Published: January 2005

Using a method employing front‐surface fura‐2 fluorometry to measure the cytosolic Ca2+ concentration, [Ca2+]i, the mechanism of endothelium‐dependent regulation of vascular tone by thrombin was studied in porcine renal interlobar arterial strips.
At concentrations lower than 3 u ml−1, thrombin evoked only early transient relaxation, while at 3 u ml−1 and higher concentrations, thrombin caused an early relaxation and a subsequent transient contraction. Both thrombin‐induced relaxation and contraction were abolished by removing the endothelium. Similar biphasic responses were observed with a protease‐activated receptor‐1‐activating peptide.
Early relaxation was associated with a decrease in [Ca2+]i, while the transient contraction was not associated with a change in [Ca2+]i of smooth muscle cells.
A thromboxane A2 (TXA2)/prostaglandin H2 (PGH2) receptor antagonist (10−5 M ONO‐3708) completely inhibited the thrombin‐induced contraction, whereas a thromboxane A2 synthase inhibitor (10−5 M OKY‐046) only partly inhibited it.
When the thrombin‐induced contraction was inhibited by ONO‐3708, either pretreatment with Nω‐nitro‐L‐arginine methylester (L‐NAME) or an increase in the amount of external K+ to 40 mM did not abolish thrombin‐induced relaxation during phenylephrine‐induced sustained contraction. However, the combination of pretreatment with L‐NAME and an elevation of external K+ to 40 mM completely abolished the relaxation.
There was no significant difference in the concentration‐dependent effects of thrombin on the initial early relaxation between conditions in which the contractile components either were or were not inhibited.
Thrombin is thus considered to mainly activate protease‐activated receptor‐1 and cause a biphasic response, early relaxation and a transient contraction, in the porcine renal interlobar artery in an endothelium‐dependent manner. The thrombin‐induced endothelium‐dependent relaxation was mediated by nitric oxide and hyperpolarizing factors, while the contraction was mediated by TXA2 and PGH2.

British Journal of Pharmacology (2000) 131, 1635–1642; doi:10.1038/sj.bjp.0703737
Sarcoplasmic reticulum function and carnitine palmitoyltransferase‐1 inhibition during progression of heart failure
Authors: Rupp Heinz , Vetter Roland 
Published: January 2005

Failing cardiac hypertrophy is associated with an inadequate sarcoplasmic reticulum (SR) function. The hypothesis was examined that pressure overloaded hearts fail to increase SR Ca2+ uptake rate proportionally to the hypertrophy and that carnitine palmitoyltransferase‐1 inhibition by etomoxir ((±)‐ethyl 2[6(4‐chlorophenoxy)hexyl] oxirane‐2‐carboxylate) can counteract this process.
Severe left ventricular pressure overload was induced in rats by constricting the ascending aorta for 8, 10, 14 and 28 weeks leading to cardiac hypertrophy (+62–+103% of sham‐operated rats) and pulmonary congestion. Homogenate oxalate‐facilitated SR Ca2+ uptake rate g wet wt−1 was reduced (P<0.05) by 29.9±1.8% irrespective of phospholamban phosphorylation (in the presence of catalytic subunit of protein kinase A) and inhibition of SR Ca2+ release channel by ruthenium red. SERCA2 protein level was reduced (P<0.05) by 30.4±0.8%.
SR Ca2+ uptake rate was inversely correlated (P<0.05) with left ventricular weight but was not affected by the occurrence of pulmonary congestion. Because SR Ca2+ uptake rate of whole ventricles was not reduced, a hypertrophy proportional dilution of SR Ca2+ uptake has to be inferred which precedes pulmonary congestion.
Treatment with etomoxir (15 mg kg body wt−1 day−1 for 10 weeks) did not affect left ventricular weight but decreased (P<0.05) the right ventricular hypertrophy related to pulmonary congestion. In parallel, SR Ca2+ uptake rate of left ventricle and myosin isozyme V1 were increased (P<0.05).
Etomoxir represents a candidate approach for prevention of heart failure by inducing a hypertrophy proportional increase in SR Ca2+ uptake rate.

British Journal of Pharmacology (2000) 131, 1748–1756; doi:10.1038/sj.bjp.0703741
Pharmacological characterization of the 5‐HT receptor‐mediated contraction in the mouse isolated ileum
Authors: Tuladhar B R , Womack M D , Naylor R J 
Published: January 2005

The pharmacological characterization of a 5‐HT receptor‐mediated contractile response in the mouse isolated ileum is described.
In the presence of methysergide (1 μM), 5‐hydroxytryptamine (5‐HT, 0.3–100 μM) produced phasic concentration‐dependent contractions of segments of the mouse isolated ileum with a pEC50 value of 5.47±0.09.
The 5‐HT3 receptor selective agonists m‐chlorophenylbiguanide (0.3–100 μM, pEC50 5.81±0.04), 1‐phenylbiguanide (3–100 μM, pEC50 5.05±0.06) and 2‐methyl‐5‐HT (3–100 μM, pEC50 5.00±0.07) acted as full agonists to induce contractile responses. 5‐methoxytryptamine (0.1–100 μM), RS 67506 (0.1–100 μM) and α‐methyl‐5‐HT (0.1–100 μM) failed to mimic the 5‐HT responses.
The contractile response to 5‐HT was not antagonized by either 5‐HT2 receptor antagonists ritanserin (0.1 μM) or ketanserin (1 μM) nor the 5‐HT4 receptor antagonist SB 204070 (0.1 μM).
The 5‐HT3 receptor selective antagonists granisetron (0.3–1 nM), tropisetron (1–10 nM), ondansetron (10 nM–1 μM) and MDL 72222 (10 nM–1 μM) caused rightward displacement of the concentration‐response curves to 5‐HT. The lower concentrations of the antagonists caused approximate parallel rightward shifts of the concentration‐response curves to 5‐HT with apparent pKB values for granisetron (9.70±0.39), tropisetron (9.18±0.20), ondansetron (8.84±0.24) and MDL 72222 (8.65±0.35). But higher concentrations of antagonists resulted in a progressive reduction in the maximum responses.
The contractile response to 5‐HT was abolished by tetrodotoxin (0.3 μM); atropine (0.1 and 1 μM) decreased the maximum response of the 5‐HT concentration‐response curve by approximately 65%.
It is concluded that a neuronally located 5‐HT3 receptor mediates a contractile response to 5‐HT in the mouse ileum. The 5‐HT3 receptor in the mouse ileum has a different pharmacological profile to that reported for the guinea‐pig ileum.

British Journal of Pharmacology (2000) 131, 1716–1722; doi:10.1038/sj.bjp.0703747
Bradykinin regulation of salt transport across mouse inner medullary collecting duct epithelium involves activation of a Ca2+‐dependent Cl− conductance
Authors: Kose H , Boese S H , Glanville M , Gray M A , Brown C D A , Simmons N L 
Published: January 2005

The mechanism by which bradykinin regulates renal epithelial salt transport has been investigated using a mouse inner medullary renal collecting duct cell‐line mIMCD‐K2.
Using fura‐2 loaded mIMCD‐K2 cells bradykinin (100 nM) has been shown to induce a transient increase in intracellular Ca2+ via activation of bradykinin B2 receptors localized to both the apical and basolateral epithelial cell surfaces.
In mIMCD‐K2 epithelial cell‐layers clamped in Ussing chambers, 100 nM bradykinin via apical and basolateral bradykinin B2 receptors stimulated a transient increase in inward short‐circuit current (Isc) of similar duration to the increase in intracellular Ca2+.
Replacements of the bathing solution Na+ by the impermeant cation, N‐methyl‐D‐glucamine and of Cl− and HCO3− by the impermeant anion gluconate at either the apical (no reduction) or basal bathing solutions (abolition of the response) are consistent with the bradykinin‐stimulated increase in inward Isc resulting from basal to apical Cl− (anion) secretion.
Using the slow whole cell configuration of the patch‐clamp technique, bradykinin was shown to activate a transient Cl− selective whole cell current which showed time‐dependent activation at positive membrane potentials and time‐dependent inactivation at negative membrane potentials. These currents were distinct from those activated by forskolin (CFTR), but identical to those activated by exogenous ATP and are therefore consistent with bradykinin activation of a Ca2+‐dependent Cl− conductance.
The molecular identity of the Ca2+‐dependent Cl− conductance has been investigated by an RT–PCR approach. Expression of an mRNA transcript with 96% identity to mCLCA1/2 was confirmed, however an additional but distinct mRNA transcript with only 81% of the identity to mCLCA1/2 was identified.

British Journal of Pharmacology (2000) 131, 1689–1699; doi:10.1038/sj.bjp.0703749
Inhibition of endotoxin‐induced vascular hyporeactivity by 4‐amino‐tetrahydrobiopterin
Authors: Gibraeil Hanan D , Dittrich Peter , Saleh Samira , Mayer Bernd 
Published: January 2005

The 4‐amino analogue of tetrahydrobiopterin (4‐ABH4) is a potent pterin‐site inhibitor of nitric oxide synthases (NOS). Although 4‐ABH4 does not exhibit selectivity between purified NOS isoforms, a pronounced selectivity of the drug towards inducible NOS (iNOS) is apparent in intact cells. This work was carried out to investigate the potential iNOS selectivity of 4‐ABH4 in isolated pig pulmonary and coronary arteries.
Endothelium‐dependent relaxations of pig pulmonary and coronary artery strips to bradykinin or calcium ionophore A23187 were inhibited by 4‐ABH4 in a concentration‐dependent manner. Half‐maximal inhibition was observed at 60–65 μM (pulmonary artery) and 200–250 μM 4‐ABH4 (coronary artery).
Pig coronary artery strips precontracted with 0.1 μM 9, 11‐dideoxy‐9, 11‐methanoepoxy‐prosta‐glandin F2α (U46619) showed a time‐dependent relaxation (monitored for up to 18 h) upon incubation with 1 μg ml−1 lipopolysaccharide (LPS). Addition of 10 μM 4‐ABH4 1 h after LPS led to a pronounced inhibition of the LPS‐triggered relaxation, whereas the pterin antagonist had no effect when given4 h after LPS.
Incubation of pulmonary and coronary artery strips with 1 μg ml−1 LPS attenuated contractile responses to norepinephrine (1 μM) and U46619 (0.1 μM). This hyporeactivity of the blood vessels to vasoconstrictor agents was inhibited by 4‐ABH4 in a concentration‐dependent manner [IC50=17.5±5.9 μM (pulmonary artery) and 20.7±3 μM (coronary artery)]. The effect of 0.1 mM 4‐ABH4 was antagonized by coincubation with 0.1 mM sepiapterin, which is known to supply intracellular BH4 via a salvage pathway.
These results demonstrate that 4‐ABH4 is a fairly selective inhibitor of iNOS in an in vitro model of endotoxaemia, suggesting that this drug and/or related pterin‐site NOS inhibitors may be useful to increase blood pressure in severe infections associated with a loss of vascular responsiveness to constrictor agents caused by endotoxin‐triggered iNOS induction in the vasculature.

British Journal of Pharmacology (2000) 131, 1757–1765; doi:10.1038/sj.bjp.0703752
Effects of the PAF receptor antagonist UK74505 on local and remote reperfusion injuries following ischaemia of the superior mesenteric artery in the rat
Authors: Souza D G , Cara D C , Cassali G D , Coutinho S F , Silveira M R , Andrade S P , Poole S P , Teixeira M M 
Published: January 2005

The effects of the long lasting and potent PAF receptor antagonist UK74505 were assessed on the local and remote injuries following ischaemia and reperfusion (I/R) of the superior mesenteric artery (SMA) in rats.
In a severe model of ischaemia (120 min) and reperfusion (120) injury, in addition to the local and remote increases in vascular permeability and neutrophil accumulation, there was significant tissue haemorrhage, blood neutropenia, systemic hypotension and elevated local and systemic TNF‐α levels.
Post‐ischaemic treatment with the selectin blocker fucoidin (10 mg kg−1) prevented neutrophil accumulation in tissue and, in consequence, all the local and systemic injuries following severe I/R.
Treatment with an optimal dose of UK74505 (1 mg kg−1) also reversed local and remote neutrophil accumulation, increases in vascular permeability and intestinal haemorrhage. UK74505 partially inhibited blood neutropenia and reperfusion‐induced hypotension.
Interestingly, both fucoidin and UK74505 prevented the local, but not systemic, increases of TNF‐α levels following severe I/R injury, demonstrating an important role of migrating cells for the local production of TNF‐α. However, the results do not support a role for PAF as an intermediate molecule in the production of systemic TNF‐α.
The beneficial effects of UK74505 and other PAF receptor antagonists in models of I/R injury in animals and the safety of UK74505 use in man warrant further investigations of the use of this drug as preventive measure for I/R injury in humans.

British Journal of Pharmacology (2000) 131, 1800–1808; doi:10.1038/sj.bjp.0703756
Local regulation of [3H]‐noradrenaline release from the isolated guinea‐pig right atrium by P2X‐receptors located on axon terminals
Authors: Sperlágh Beáta , Erdélyi Ferenc , Szabó Gábor , Vizi E Sylvester 
Published: January 2005

In this study the regulation of cardiac sympathetic outflow by presynaptic P2X receptor‐gated ion channels was examined.
ATP (30 μM–1 mM) and other P2‐receptor agonists elicited [3H]‐noradrenaline ([3H]‐NA) outflow from the isolated guinea‐pig right atrium with the potency order of ATP>2‐methyl‐thioATP>α,β‐methylene‐ATP=ADP, whereas β,γ‐methylene‐L‐ATP was inactive.
Ca2+‐free conditions abolished both electrical field stimulation (EFS)‐ and ATP‐evoked release of tritium. Unlike from EFS‐induced outflow, ATP‐induced [3H]‐NA outflow was not reduced by ω‐Conotoxin‐GVIA (100 nM), Cd2+ (100 μM) and tetrodotoxin (1 μM).
The rapid extracellular decomposition of ATP was revealed by HPLC analysis. However, the effect of ATP to promote [3H]‐NA release was not prevented by 8‐cyclopentyl‐1,3‐dipropylxanthine (DPCPX, 250 nM), 3,7‐dimethyl‐1‐propargylxanthine (DMPX, 250 nM), or by reactive blue 2 (RB2, 10 μM), antagonists of A1‐, A2‐ and inhibitory P2 receptors.
Zn2+ (50 μM), the P2X‐receptor modulator potentiated, and P2X receptor antagonists, i.e. suramin (300 μM), pyridoxal‐phosphate‐6‐azophenyl‐2′,4′‐disulphonic acid (PPADS, 30 μM) and 2′‐o‐(trinitrophenyl)‐adenosine 5′‐triphosphate (TNP‐ATP, 30 μM) antagonized the ATP (1 mM)‐evoked response.
RT–PCR study revealed the expression of P2X2 and P2X3 receptor mRNAs in guinea‐pig superior cervical ganglion.
PPADS (30 μM) significantly reduced the EFS‐induced [3H]‐NA outflow in the presence DPCPX (250 nM) and RB2 (10 μM).
In summary a P2X‐type purinoceptor regulates noradrenaline release from the isolated right atrium of the guinea‐pig. The pharmacological profile of the receptor resemble to homo‐oligomeric P2X3 or hetero‐oligomeric P2X2/P2X3 complexes, and provide a new target to intervene on sympathetic neuroeffector transmission at the presynaptic site.

British Journal of Pharmacology (2000) 131, 1775–1783; doi:10.1038/sj.bjp.0703757
Selective phenylalkylamine block of IKr over other K+ currents in guinea‐pig ventricular myocytes
Authors: Jones Stephen E , Missan Sergey , Zhabyeyev Pavel , McDonald Terence F 
Published: January 2005

Previous studies on verapamil and D600 have established that the Ca2+‐channel blockers also inhibit delayed‐rectifier K+ currents in cardiac tissues and myocytes. However, estimated IC50 values range over two to three orders of concentration, and it is unclear whether this reflects a high selectivity by one or both of the phenylalkylamines for particular K+ channels. The purpose of the present study was to determine the concentration‐dependent actions of verapamil and D600 on three defined cardiac K+ currents.
Guinea‐pig ventricular myocytes in the conventional whole‐cell configuration were bathed with normal Tyrode's or K+‐free solution, and pulsed from −80 mV for measurement of the effects of 0.01 μM to 3 mM verapamil and D600 on the inwardly‐rectifying K+ current (IKl) and the two delayed‐rectifier K+ currents, rapidly‐activating IKr and slowly‐activating IKs.
The phenylalkylamines inhibited both inward‐ and outward‐directed IKl. The IC50 values for outward IKl were approximately 220 μM.
Verapamil and D600 were approximately equipotent inhibitors of the delayed‐rectifier K+ currents. They inhibited IKr with IC50 near 3 μM, and IKs with IC50 280 μM. These results are discussed in relation to previous findings on K+ currents and to the clinical actions of the drugs.

British Journal of Pharmacology (2000) 131, 1809–1816; doi:10.1038/sj.bjp.0703758
Novel mechanism of blocking axonal Na+ channels by three macrocyclic polyamine analogues and two spider toxins
Authors: Yakehiro Masuhide , Furukawa Yasuo , Koike Tohru , Kimura Eiichi , Nakajima Terumi , Yamaoka Kaoru , Seyama Issei 
Published: January 2005

The mechanism of Na+ channel block by three macrocyclic polyamine derivatives and two spider toxins was studied with voltage clamp and internal perfusion method in squid axons.
All these chemicals specifically block Na+ channels in the open state only from the internal surface, and do not affect K+ channels.
The blocking effect is enhanced as the depolarizing pulse becomes larger. Blocked channels are unable to shift to the inactivated state.
In the case of cyclam and guanidyl‐side armed cyclam (G‐cyclam), quick release of these chemicals from the binding sites is proven by the increase in the tail current and prolongation of the time course of the off gating current. On the other hand, in the presence of N‐4 and the spider toxins, their detachment was delayed significantly.
Molecular requirements for the block of Na+ channels by these molecules are the presence of positive charge and hydrophobicity.

British Journal of Pharmacology (2001) 132, 63–72; doi:10.1038/sj.bjp.0703765
Characterization of a novel mechanism accounting for the adverse cholinergic effects of the anticancer drug irinotecan
Authors: Blandizzi Corrado , De Paolis Barbara , Colucci Rocchina , Lazzeri Gloria , Baschiera Fabio , Del Tacca Mario 
Published: January 2005

This study investigates the mechanisms accounting for the adverse cholinergic effects of the antitumour drug irinotecan. The activity of irinotecan and its active metabolite, 7‐ethyl‐10‐hydroxy‐camptothecin (SN‐38), was assayed in models suitable for pharmacological studies on cholinergic system.
Irinotecan moderately inhibited human or electric eel acetylcholinesterase activity, SN‐38 had no effect, whereas physostigmine blocked both the enzymes with high potency and efficacy.
Irinotecan and SN‐38 did not affect spontaneous or electrically‐induced contractile activity of human colonic muscle. Acetylcholine and dimethylphenylpiperazinium (DMPP) caused phasic contractions or relaxations, respectively. Physostigmine enhanced the motor responses elicited by electrical stimulation.
Although irinotecan and SN‐38 did not modify the basal contractile activity of guinea‐pig ileum longitudinal muscle strips, irinotecan 100 μM moderately enhanced cholinergic twitch contractions. Acetylcholine or DMPP caused phasic contractions, whereas physostigmine enhanced the twitch responses. Electrically‐induced [3H]‐acetylcholine release was reduced by irinotecan (100 μM) or physostigmine (0.1 μM).
Intravenous irinotecan stimulated gastric acid secretion in rats, but no effects were obtained with SN‐38, physostigmine or i.c.v. irinotecan. Hypersecretion induced by irinotecan was partly prevented by ondansetron, and unaffected by capsazepine. In the presence of atropine, vagotomy and systemic or vagal ablation of capsaicin‐sensitive afferent fibres, irinotecan did not stimulate gastric secretion.
The present results indicate that irinotecan and SN‐38 do not act as specific acetylcholinesterase blockers or acetylcholine receptor agonists. It is rather suggested that irinotecan promotes a parasympathetic discharge to peripheral organs, mediated by capsaicin‐sensitive vagal afferent fibres, and that serotonin 5‐HT3 receptors are implicated in the genesis of vago‐vagal reflex triggered by irinotecan.

British Journal of Pharmacology (2001) 132, 73–84; doi:10.1038/sj.bjp.0703766