bluuebunny/crossref_metadata_2025 huggingface dataset:
Pharmacological block of the slow component of the outward delayed rectifier current (IKs) fails to lengthen rabbit ventricular muscle QTc and action potential duration
Authors: Lengyel Csaba , Iost Norbert , Virág László , Varró András , Lathrop David A , Papp Julius Gy
Published: January 2005

The effects of IKs block by chromanol 293B and L‐735,821 on rabbit QT‐interval, action potential duration (APD), and membrane current were compared to those of E‐4031, a recognized IKr blocker. Measurements were made in rabbit Langendorff‐perfused whole hearts, isolated papillary muscle, and single isolated ventricular myocytes.

Neither chromanol 293B (10 μM) nor L‐735,821 (100 nM) had a significant effect on QTc interval in Langendorff‐perfused hearts. E‐4031 (100 nM), on the other hand, significantly increased QTc interval (35.6±3.9%, n=8, P<0.05).

Similarly both chromanol 293B (10 μM) and L‐735,821 (100 nM) produced little increase in papillary muscle APD (less than 7%) while pacing at cycle lengths between 300 and 5000 ms. In contrast, E‐4031 (100 nM) markedly increased (30 – 60%) APD in a reverse frequency‐dependent manner.

In ventricular myocytes, the same concentrations of chromanol 293B (10 μM), L‐735,821 (100 nM) and E‐4031 (1 μM) markedly or totally blocked IKs and IKr, respectively.

IKs tail currents activated slowly (at +30 mV, τ=888.1±48.2 ms, n=21) and deactivated rapidly (at −40 mV, τ=157.1±4.7 ms, n=22), while IKr tail currents activated rapidly (at +30 mV, τ=35.5±3.1 ms, n=26) and deactivated slowly (at −40 mV, τ1=641.5±29.0 ms, τ2=6531±343, n=35). IKr was estimated to contribute substantially more to total current density during normal ventricular muscle action potentials (i.e., after a 150 ms square pulse to +30 mV) than does IKs.

These findings indicate that block of IKs is not likely to provide antiarrhythmic benefit by lengthening normal ventricular muscle QTc, APD, and refractoriness over a wide range of frequencies.

British Journal of Pharmacology (2001) 132, 101–110; doi:10.1038/sj.bjp.0703777
Vasoconstrictor actions of isoprostanes via tyrosine kinase and Rho kinase in human and canine pulmonary vascular smooth muscles
Authors: Janssen L J , Premji M , Netherton S , Coruzzi J , Lu‐Chao H , Cox P G
Published: January 2005

We examined the effects of several E‐ring and F‐ring isoprostanes on mechanical activity in pulmonary artery and vein.

8‐iso PGE2 and 8‐iso PGF2α were powerful spasmogens in human vasculature and in canine pulmonary vein. 8‐iso PGE1 and 8‐iso PGF2β also exhibited moderate spasmogenic activity in canine pulmonary vein; 8‐iso PGF1α, 8‐iso PGF1β, and 8‐iso PGF3α were generally ineffective. Canine pulmonary arteries did not exhibit excitatory responses to any of the isoprostanes.

The spasmogenic effects of 8‐iso PGE2 were markedly attenuated by the TP‐receptor blocker ICI 192605 and by the EP‐receptor blocker AH 6809 (−log KB=8.4 and 5.7, respectively). PGE2 was a very weak agonist (∼100 fold less so than 8‐iso PGE2).

In the presence of ICI 192605 (10−6 M), 8‐iso PGE1 evoked modest dose‐dependent relaxations in human and canine pulmonary vein, and in canine pulmonary artery, but not in the human pulmonary artery. The other isoprostanes were generally ineffective as vasodilators in the pulmonary vasculature of both species.

The spasmogenic effects of 8‐iso PGE2 and 8‐iso PGF2α did not involve elevation of [Ca2+]i.

8‐iso PGE2‐evoked contractions were blocked by inhibitors of tyrosine kinase (genistein) and Rho kinase (Y 27632 and HA 1077), but not by inhibitors of protein kinase C (calphostin C or chelerythrine), mitogen‐activated protein kinase kinase (PD 98059) or p38‐kinase (SB 203580).

The actions of 8‐isoprostanes in the lungs are compound‐, species‐ and tissue‐dependent. Several isoprostanes evoke vasoconstriction: in the case of 8‐iso PGE2, this involves activation of TP‐receptors, tyrosine kinases and Rho kinases. 8‐iso PGE1 is also able to cause vasodilation.

British Journal of Pharmacology (2001) 132, 127–134; doi:10.1038/sj.bjp.0703784
Modulation of cell adhesion and viability of cultured murine bone marrow cells by arsenobetaine, a major organic arsenic compound in marine animals
Authors: Sakurai Teruaki , Fujiwara Kitao
Published: January 2005

In this study, we investigated the biological effects of trimethyl (carboxymethyl) arsonium zwitterion, namely arsenobetaine (AsBe), which is a major organic arsenic compound in marine animals using murine bone marrow (BM) cells and compared them with those of an inorganic arsenical, sodium arsenite, in vitro.

Sodium arsenite showed strong cytotoxicity in BM cells, and its IC50 was 6 μM. In contrast, AsBe significantly enhanced the viability of BM cells in a dose‐dependent manner during a 72‐h incubation; about a twofold increase in the viability of cells compared with that of control cells cultured with the medium alone was observed with a μM level of AsBe.

In morphological investigations, AsBe enhanced the numbers of large mature adherent cells, especially granulocytes, during a 72‐h BM culture. When BM cells were cultured together with AsBe and a low dose (1 u ml−1) of recombinant murine granulocyte/macrophage colony‐stimulating factor (rMu GM‐CSF), significant additive‐like increasing effects were observed on the numbers of both granulocytes and macrophages originated from BM cells. However, AsBe did not cause proliferation of BM cells at all as determined by colony‐forming assay using a gelatious medium.

These findings demonstrate the unique and potent biological effects in mammalian cells of AsBe, a major organic arsenic compound in various marine animals which are ingested daily as seafood in many countries.

British Journal of Pharmacology (2001) 132, 143–150; doi:10.1038/sj.bjp.0703790
Pharmacokinetic‐pharmacodynamic modelling in the early development phase of anti‐psychotics: a comparison of the effects of clozapine, S 16924 and S 18327 in the EEG model in rats
Authors: Parker T J , Della Pasqua O E , Loizillon E , Chezaubernard C , Jochemsen R , Danhof M
Published: January 2005

The use of pharmacokinetic/pharmacodynamic (PK/PD) analysis in early compound development was investigated in the rat for two developmental anti‐psychotic compounds with clozapine as a positive control.

Three plasma samples were collected from each of eight animals according to a pre‐defined sampling matrix allowing a total of 12 time points for PK analysis. Quantitative electroencephalography (QEEG), particularly the theta and beta frequencies, was used as a measurement of pharmacological effect.

PK/KD modelling of the sparse PK data available relative to a rich set of PD data was achieved using a population approach in NONMEM (IV). Individual PK parameter estimates were incorporated into a PK/PD model.

Qualitative EEG changes in rat and human were similar for clozapine, but different for the two developmental compounds, suggesting that changes in these PD parameters may not be specifically related to the anti‐psychotic activity.

Although no definitive data are available concerning the signal specificity of EEG frequency bands with respect to dopaminergic or serotonergic receptor activity, qualitative and quantitative differences seen in EEG parameters are likely to result from the multiple receptor occupancy for these compounds.

The results confirm the value of population PK/PD modelling in conjunction with sparse sampling to enable determination of concentration effect relationships in the pre‐clinical development programme of CNS‐active drugs.

British Journal of Pharmacology (2001) 132, 151–158; doi:10.1038/sj.bjp.0703791
Simvastatin inhibits noradrenaline‐induced hypertrophy of cultured neonatal rat cardiomyocytes
Authors: Luo Jian‐Dong , Xie Fang , Zhang Wei‐Wen , Ma Xiao‐Dong , Guan Jin‐Xia , Chen Xiu
Published: January 2005

Oxidative mechanisms have been implicated in neonatal cardiomyocyte hypertrophy. We and others have shown that a HMG‐CoA reductase inhibitor preserves endogenous antioxidant enzyme activity and inhibits cardiac hypertrophy in vivo. We therefore have examined whether noradrenaline (NA) induces the generation of reactive oxygen species (ROS) during its induction of neonatal cardiomyocyte hypertrophy and whether simvastatin, a HMG‐CoA reductase inhibitor, attenuates ROS production and thus NA‐induced hypertrophy of cardiomyocytes.

NA increased the intracellular ROS levels in a concentration‐dependent manner. This increase of ROS was significantly inhibited by simvastatin and catalase. Prazosin partially suppressed NA‐induced increase of ROS and beating, while preincubation with both prazosin and propranolol completely abolished NA‐evoked increase of ROS and beating. Simvastatin did not affect NA‐induced increase of beating.

The NA‐induced increase of protein content was partially suppressed by prazosin and completely abolished by preincubation with both prazosin and propranolol. Simvastatin inhibited the increase of NA‐induced increase of RNA content and [3H]‐leucine incorporation in a concentration‐dependent manner. Mevalonic acid (MVA) reversed the inhibition of NA‐induced RNA and protein increase by simvastatin. Catalase also inhibited the NA‐induced increase of RNA and protein.

We conclude that the inhibitory effects of simvastatin on myocyte hypertrophy were associated with its antioxidant effects and inhibition of MVA‐metabolism pathway in neonatal rat cardiomyocytes. NA‐induced increases of intracellular ROS and cardiomyocyte hypertrophy requires both α and β adrenoceptors activation in neonatal rat cardiomyocytes. The increases of ROS induced by NA is required for hypertrophy.

British Journal of Pharmacology (2001) 132, 159–164; doi:10.1038/sj.bjp.0703792
Knockdown of spinal metabotropic glutamate receptor 1 (mGluR1) alleviates pain and restores opioid efficacy after nerve injury in rats
Authors: Fundytus Marian E , Yashpal Kiran , Chabot Jean‐Guy , Osborne Michael G , Lefebvre Celeste D , Dray Andy , Henry James L , Coderre Terence J
Published: January 2005

Nerve injury often produces long‐lasting spontaneous pain, hyperalgesia and allodynia that are refractory to treatment, being only partially relieved by clinical analgesics, and often insensitive to morphine. With the aim of assessing its therapeutic potential, we examined the effect of antisense oligonucleotide knockdown of spinal metabotropic glutamate receptor 1 (mGluR1) in neuropathic rats.

We chronically infused rats intrathecally with either vehicle, or 50 μg day−1 antisense or missense oligonucleotides beginning either 3 days prior to or 5 days after nerve injury. Cold, heat and mechanical sensitivity was assessed prior to any treatment and again every few days after nerve injury.

Here we show that knockdown of mGluR1 significantly reduces cold hyperalgesia, heat hyperalgesia and mechanical allodynia in the ipsilateral (injured) hindpaw of neuropathic rats.

Moreover, we show that morphine analgesia is reduced in neuropathic rats, but not in sham‐operated rats, and that knockdown of mGluR1 restores the analgesic efficacy of morphine.

We also show that neuropathic rats are more sensitive to the excitatory effects of intrathecally injected N‐methyl‐D‐aspartate (NMDA), and have elevated protein kinase C (PKC) activity in the spinal cord dorsal horn, two effects that are reversed by knockdown of mGluR1.

These results suggest that activity at mGluR1 contributes to neuropathic pain through interactions with spinal NMDA receptors and PKC, and that knockdown of mGluR1 may be a useful therapy for neuropathic pain in humans, both to alleviate pain directly, and as an adjunct to opioid analgesic treatment.

British Journal of Pharmacology (2001) 132, 354–367; doi:10.1038/sj.bjp.0703810
Effect of 4‐trifluoromethyl derivatives of salicylate on nuclear factor κB‐dependent transcription in human astrocytoma cells
Authors: Hernández Marita , Arriba Alberto Fernández de , Merlos Manel , Fuentes Lucía , Crespo Mariano Sánchez , Nieto María Luisa
Published: January 2005

The effect of two derivatives of salicylate, 2‐hydroxy‐4‐trifluoromethylbenzoic acid (HTB) and 2‐acetoxy‐4‐trifluoromethylbenzoic acid (triflusal), on the expression of several proteins displaying pro‐inflammatory activities the regulation of which is associated to the transcription factor NF‐κB, was assayed in the human astrocytoma cell line 1321N1.

Tumour necrosis factor‐α (TNF‐α) activated NF‐κB as judged from both the appearance of κB‐binding activity in the nuclear extracts, the degradation of IκB proteins in the cell lysates, and the activation of IκB kinases using an immunocomplex kinase assay with glutathione S‐transferase (GST)‐IκB proteins as substrates.

HTB up to 3 mM did not inhibit the nuclear translocation of NK‐κB/Rel proteins as judged from electrophoretic mobility‐shift assays; however, HTB inhibited the degradation of IκBβ without significantly affecting the degradation of both IκBα and IκBε.

In keeping with their inhibitory effect on IκBβ degradation in the cell lysates, both HTB and triflusal inhibited the phosphorylation of GST‐IκBβ elicited by TNF‐α, without affecting the phosphorylation of GST‐IκBα.

The effect of both HTB and triflusal on κB‐dependent trans‐activation was studied by assaying the expression of both cyclo‐oxygenase‐2 (COX‐2) and vascular cell adhesion molecule‐1 (VCAM‐1). HTB and triflusal inhibited in a dose‐dependent manner the expression of COX‐2 and VCAM‐1 mRNA and the induction of COX‐2 protein at therapeutically relevant concentrations.

These findings show the complexity of the biochemical mechanisms underlying the activation of NF‐κB in the different cell types and extend the anti‐inflammatory effects of HTB and triflusal to neural cells.

British Journal of Pharmacology (2001) 132, 547–555; doi:10.1038/sj.bjp.0703820
Effects of extracellular nucleotides and nucleosides on prostate carcinoma cells
Authors: Janssens Rodolphe , Boeynaems Jean‐Marie
Published: January 2005

The purpose of this work was to characterize the receptors involved in the action of nucleotides on the human prostate carcinoma cell lines LNCaP, PC‐3 and DU145.

Northern blotting revealed the presence of P2Y2, P2Y6 and P2Y11 messengers in the three cell lines. P2Y1 mRNA was only observed in the DU145 cells. In both PC‐3 and DU145 cells, ATP and UTP stimulated inositol phosphate accumulation in an equipotent, equiactive and non‐additive way, suggesting the involvement of P2Y2 receptors. ATP also increased cyclic AMP, but this effect is likely to result from degradation into adenosine and activation of A2 receptor. A2 receptor activation led to a synergistic enhancement of prostate‐specific antigen secretion induced by vasoactive intestinal peptide.

RT – PCR experiments detected the expression of the P2X4 and P2X5 receptors in the DU145 cells and the P2X4, P2X5 and P2X7 receptors in the PC‐3 cells. The calcium influx induced by BzATP confirmed the functional expression of P2X receptors.

ATP inhibited the growth of PC‐3 and DU145 cells. This effect was mimicked neither by UTP nor by adenosine, indicating that it does not result from phospholipase C or adenylyl cyclase activation. On the contrary, in PC‐3 cells, BzATP reproduced the effect of ATP, which was associated to a moderate decrease of proliferation and an increase of apoptosis. In DU145 cells, ATP was more potent than BzATP and growth inhibition was mainly associated with necrosis. We suggest that P2X receptors might be involved in the inhibition by nucleotides of prostate carcinoma cell growth.

British Journal of Pharmacology (2001) 132, 536–546; doi:10.1038/sj.bjp.0703833
Nitric oxide‐mediated modulation of the endothelin‐1 signalling pathway in the human cardiovascular system
Authors: Wiley Katherine E , Davenport Anthony P
Published: January 2005

We studied the ability of nitric oxide (NO) to physiologically antagonize endothelin‐1 (ET‐1) induced constrictions in human internal mammary artery (IMA). We also investigated the hypothesis that NO interacts directly with ET‐receptor binding in human heart and aorta.

ET‐1 potently contracted IMA (EC50 6.86 nM, 95% CI: 3.5 – 13.4 nM; n=12). The constrictor response to 10 nM ET‐1 was fully reversed by the NO‐donor diethylamine NONOate (DEA/NO; EC50 2.0 μM, 95% CI: 0.8 – 4.8 μM; n=5). The guanylate cyclase inhibitor ODQ (100 μM) reduced the response to DEA/NO but did not abolish it (EMAX 50.9±8.5% in the presence of ODQ; 113.0±8.4%, control).

The increase in cyclic GMP by 30 μM DEA/NO was abolished in the presence of 100 μM ODQ (n=6).

In saturation binding experiments the NO‐donor Diethyltriamine NONOate (DETA/NO; 1 mM) caused a 90% reduction in maximum binding of [125I]‐ET‐1 in human heart, without affecting the affinity. This reduction in binding was abolished by haemoglobin. Pre‐incubating either the radiolabel or the tissue with NO‐donors did not reduce binding. A similar effect was observed in aortic smooth muscle.

We have shown that DEA/NO is able to reverse ET‐1‐induced contractions in the human vasculature. The binding studies suggest a direct interaction between NO and the ET receptor or receptor‐ligand complex in human ventricular and aortic tissue. NO is released continuously in vivo, thus this apparent modification of ET‐receptor binding may provide an additional mechanism by which NO counter‐balances the effects of ET.

British Journal of Pharmacology (2001) 132, 213–220; doi:10.1038/sj.bjp.0703834
A comparison of the effect of nitroparacetamol and paracetamol on liver injury
Authors: Futter L E , Al‐Swayeh O A , Moore P K
Published: January 2005

Paracetamol (5 mmol kg−1, i.p.) caused liver damage in rats as indicated by increased plasma aspartate aminotransferase (AST), alanine aminotransferase (ALT) and glutamate dehydrogenase (GDH) activities. No change in plasma bilirubin or creatinine was noted. An equimolar dose of nitroparacetamol (a nitric oxide (NO)‐releasing derivative of paracetamol) did not alter plasma levels of any of the markers of liver/kidney damage. No difference in plasma or liver paracetamol was apparent in animals injected with paracetamol or nitroparacetamol. These results indicate that NO released from nitroparacetamol exhibits hepatoprotective activity in these animals and suggest that nitroparacetamol may therefore be considered as a safer alternative to paracetamol in the clinic.

British Journal of Pharmacology (2001) 132, 10–12; doi:10.1038/sj.bjp.0703837
Chlorpromazine inhibits store‐operated calcium entry and subsequent noradrenaline secretion in PC12 cells
Authors: Choi Se‐Young , Kim Yong‐Hyun , Lee Yong‐Kyu , Kim Kyong‐Tai
Published: January 2005

The effect of chlorpromazine on the store‐operated Ca2+ entry activated via the phospholipase C signalling pathway was investigated in PC12 cells.

Chlorpromazine inhibited the sustained increase after the initial peak in the intracellular Ca2+ concentration produced by bradykinin while having no effect on the initial transient response. The inhibition was lowered by the removal of extracellular free Ca2+. However, chlorpromazine did not inhibit bradykinin‐induced inositol 1,4,5‐trisphosphate production.

Chlorpromazine inhibited the bradykinin‐induced noradrenaline secretion in a concentration‐dependent manner (IC50: 24±5 μM, n=3).

To test for a direct effect of chlorpromazine on store‐operated Ca2+ entry, thapsigargin, an inhibitor of microsomal Ca2+‐ATPase, was used to induce store‐operated Ca2+ entry in PC12 cells. Chlorpromazine reduced the thapsigargin‐induced sustained Ca2+ level (IC50: 24±2 μM, n=3), and the inhibition also occluded the inhibitory action of 1‐[‐[3‐(4‐methoxyphenyl) propoxy]‐4‐methoxyphenyl]‐1H‐imidazole hydrochloride (SK&F96365).

The results suggest that chlorpromazine negatively modulates the store‐operated Ca2+ entry activated subsequent to PLC activation.

British Journal of Pharmacology (2001) 132, 411–418; doi:10.1038/sj.bjp.0703840
Two subtypes of G protein‐coupled nucleotide receptors, P2Y1 and P2Y2 are involved in calcium signalling in glioma C6 cells
Authors: Sabała Paweł , Czajkowski Rafał , Przybyłek Krzysztof , Kalita Katarzyna , Kaczmarek Leszek , Barańska Jolanta
Published: January 2005

In glioma C6 cells, the stimulation of P2Y receptors by ADP, ATP and UTP initiated an increase in the intracellular Ca2+ concentration, in a process that involved the release of Ca2+ from InsP3‐sensitive store and the capacitative, extracellular Ca2+ entry. The presence of external Ca2+ was not necessary to elevate Ca2+.

The rank order of potencies of nucleotide analogues in stimulating [Ca2+]i was: 2MeSADP > ADP > 2MeSATP = 2ClATP > ATP > UTP. α,β‐Methylene ATP, adenosine and AMP were ineffective.

ADP and UTP effects were additive, while actions of ATP and UTP were not additive on [Ca2+]i increase. Similarly, cross‐desensitization between ATP and UTP but not between ADP and UTP occurred.

Suramin, a non‐specific nucleotide receptors inhibitor, antagonized ATP‐, UTP‐ and ADP‐evoked Ca2+ responses. PPADS, a selective antagonist of the P2Y1 receptor‐generated InsP3 accumulation, decreased ADP‐initiated Ca2+ response with no effect on ATP and UTP.

Pertussis toxin (PTX) reduced ADP‐ and ATP‐induced Ca2+ increases. Short‐term treatment with TPA, inhibited both ATP and ADP stimulatory effects on [Ca2+]i.

ADP inhibited isoproterenol‐induced cyclic AMP accumulation. PTX blocked this effect, but PPADS did not.

RT – PCR analysis revealed the molecular identity of P2Y receptors expressed by glioma C6 cells to be both P2Y1 and P2Y2.

It is concluded that both P2Y1 and P2Y2 receptors co‐exist in glioma C6 cells. ADP acts as agonist of the first, and ATP and UTP of the second one. Both receptors are linked to phospholipase C (PLC).

British Journal of Pharmacology (2001) 132, 393–402; doi:10.1038/sj.bjp.0703843
Influence of reduced glutathione on the proliferative response of sulfamethoxazole‐specific and sulfamethoxazole‐metabolite‐specific human CD4+ T‐cells
Authors: Burkhart Christoph , Von Greyerz Salome , Depta Jan P H , Naisbitt Dean J , Britschgi Markus , Park Kevin B , Pichler Werner J
Published: January 2005

Hypersensitivity to the drug sulfamethoxazole (SMX) is thought to be a consequence of bioactivation to the hydroxylamine metabolite (SMX‐NHOH) and further oxidation to the ultimate reactive metabolite, nitroso‐sulfamethoxazole (SMX‐NO). SMX‐NO covalently modifies self proteins which in turn might be recognized as neo‐antigens by T‐cells. The antioxidant glutathione (GSH) is known to protect cells from reactive metabolites by conjugation and subsequent dissociation to SMX‐NHOH and/or SMX.

To study the reactivity of T‐cells to SMX metabolites and their respective role in the generation of drug‐specific T‐cells, we analysed the effect of GSH on the response of PBMC to SMX and its metabolites SMX‐NHOH and SMX‐NO. Furthermore, we monitored the proliferative response of drug‐specific T‐cell clones in the presence or absence of GSH.

We found that addition of GSH to peripheral blood mononuclear cells had no effect on the SMX‐specific response but enhanced the proliferation to SMX‐metabolites. The response of SMX‐NO‐specific T‐cell clones was abrogated when GSH was present during the covalent haptenation of antigen presenting cells (APC). Conversely, SMX‐specific T‐cell clones gained reactivity through the conversion of SMX‐NO to the parent drug by GSH. While GSH had no effect on the initial activation of T‐cell clones, it prevented covalent binding to APCs, reduced toxicity and thereby led to proliferation of drug‐specific T‐cells to non‐reactive drug metabolites.

Our data support the concept that in allergic individuals T‐cells recognize the non‐covalently bound parent drug rather than APC covalently modified by SMX‐NO.

British Journal of Pharmacology (2001) 132, 623–630; doi:10.1038/sj.bjp.0703845
The effects of P2Y receptor agonists and adenosine on prostaglandin production by the guinea‐pig uterus
Authors: Aitken Heather , Poyser N L , Hollingsworth M
Published: January 2005

This study has investigated the effects adenosine 5′‐triphosphate (ATP), analogues of ATP, uridine 5′‐triphosphate (UTP) and adenosine on prostaglandin output from the guinea‐pig uterus superfused in vitro, and from guinea‐pig endometrium and myometrium cultured for 24 h.

ATP, 2‐methylthio ATP and adenosine increased the outputs of prostaglandin F2α (PGF2α) and 6‐keto‐PGF1α (reflecting PGI2 production), and UTP increased the output of PGF2α from the superfused guinea‐pig uterus. These findings support the hypothesis that the contractile effects of ATP, 2‐methylthio ATP, UTP and adenosine are mediated by prostaglandins.

Suramin (a P2 receptor antagonist) and 8‐sulphophenyltheophylline (an A receptor antagonist) blocked the stimulatory actions of ATP and adenosine, respectively, on PGF2α output, suggesting that ATP acts on P2 receptors (probably of the P2Y type) and adenosine acts on A receptors in the guinea‐pig uterus to increase PGF2α production.

ATP, 2‐methylthio ATP, α,β‐methylene ATP, β,γ‐methylene ATP, UTP and adenosine increased the output of PGF2α from guinea‐pig endometrium and myometrium after 24 h of culture, with a greater stimulatory effect being exerted on the endometrium than on the myometrium. Little or no stimulatory effect was seen after 2 and 8 h of culture. In addition the effects of ATP, ATP analogues, UTP and adenosine on the outputs of PGE2 and 6‐keto‐PGF1α from cultured endometrium and myometrium were more variable, with both stimulation and inhibition being observed.

The stimulatory effects of ATP and adenosine on PGF2α output from the endometrium and myometrium were associated with an increase in the prostaglandin synthesizing capacity of both tissues, due probably to an increase in the amount of prostaglandin H synthase present.

British Journal of Pharmacology (2001) 132, 709–721; doi:10.1038/sj.bjp.0703848
The differential effect of propofol on contractility of isolated myocardial trabeculae of rat and guinea‐pig
Authors: Klarenbosch J van , Stienen G J M , Ruijter W de , Scheffer G J , Lange J J de
Published: January 2005

The effects of propofol on myocardial contractility were studied in rat, in which the contractile activation mainly depends on calcium derived from the sarcoplasmic reticulum (SR), and guinea‐pig, in which transsarcolemmal influx of calcium plays a major role.

Intact and chemically skinned trabeculae from the right ventricle were studied. Intact trabeculae were electrically stimulated and force development during steady state and post rest contractions was measured. In saponin skinned trabeculae Ca2+ uptake and release by the SR was studied. In Triton skinned trabeculae the influence of propofol on calcium sensitivity of the myofilaments was studied.

In intact rat trabeculae propofol in concentrations of 28, 112 and 280 μM did not change peak force development nor the pattern of post rest contraction. In guinea‐pig trabeculae propofol significantly reduced peak force to respectively 64, 40 and 23% of control values and the post rest contractions were potentiated. In skinned trabeculae propofol did not affect Ca2+ handling by the SR, nor did it change force production and Ca2+ sensitivity of the myofilaments.

This study shows that, in contrast to rat, in guinea‐pig propofol directly depresses myocardial contractility, probably by decreasing transsarcolemmal Ca2+ influx. There is no significant influence of propofol on Ca2+ handling by the SR, nor on the contractile proteins.

British Journal of Pharmacology (2001) 132, 742–748; doi:10.1038/sj.bjp.0703849
Structure‐activity relationship for the endogenous cannabinoid, anandamide, and certain of its analogues at vanilloid receptors in transfected cells and vas deferens
Authors: Ross Ruth A , Gibson T Michael , Brockie Heather C , Leslie Mark , Pashmi Ghazaleh , Craib Susan J , Di Marzo Vincenzo , Pertwee Roger G
Published: January 2005

This study was directed at exploring the structure‐activity relationship for anandamide and certain of its analogues at the rat VR1 receptor in transfected cells and at investigating the relative extent to which anandamide interacts with CB1 and vanilloid receptors in the mouse vas deferens.

pKi values for displacement of [3H]‐resiniferatoxin from membranes of rVR1 transfected CHO cells were significantly less for anandamide (5.78) than for its structural analogues N‐(4‐hydroxyphenyl)‐arachidonylamide (AM404; 6.18) and N‐(3‐methoxy‐4‐hydroxy)benzyl‐arachidonylamide (arvanil; 6.77).

pEC50 values for stimulating 45Ca2+ uptake into rVR1 transfected CHO cells were significantly less for anandamide (5.80) than for AM404 (6.32) or arvanil (9.29). Arvanil was also significantly more potent than capsaicin (pEC50=7.37), a compound with the same substituted benzyl polar head group as arvanil.

In the mouse vas deferens, resiniferatoxin was 218 times more potent than capsaicin as an inhibitor of electrically‐evoked contractions. Both drugs were antagonized to a similar extent by capsazepine (pKB=6.93 and 7.18 respectively) but were not antagonized by SR141716A (1 μM). Anandamide was less susceptible than capsaicin to antagonism by capsazepine (pKB=6.02) and less susceptible to antagonism by SR141716A (pKB=8.66) than methanandamide (pKB=9.56). WIN55212 was antagonized by SR141716A (pKB=9.02) but not by capsazepine (10 μM).

In conclusion, anandamide and certain of its analogues have affinity and efficacy at the rat VR1 receptor. In the mouse vas deferens, which seems to express vanilloid and CB1 receptors, both receptor types appear to contribute to anandamide‐induced inhibition of evoked contractions.

British Journal of Pharmacology (2001) 132, 631–640; doi:10.1038/sj.bjp.0703850
Bradykinin attenuates the [Ca2+]i response to angiotensin II of renal juxtamedullary efferent arterioles via an EDHF
Authors: Marchetti Jeannine , Praddaude Françoise , Rajerison Rabary , Ader Jean‐Louis , Alhenc‐Gelas François
Published: January 2005

Bradykinin (BK) effect on the [Ca2+]i response to 1 nM angiotensin II was examined in muscular juxtamedullary efferent arterioles (EA) of rat kidney.

BK (10 nM) applied during the angiotensin II‐stimulated [Ca2+]i increase, induced a [Ca2+]i drop (73±2%). This drop was prevented by de‐endothelialization and suppressed by HOE 140, a B2 receptor antagonist. It was neither affected by L‐NAME or indomethacin, nor mimicked by sodium nitroprusside, 8‐bromo‐cyclic GMP or PGI2. The BK effect did not occur when the [Ca2+]i increase was caused by 100 mM KCl‐induced membrane depolarization and was abolished by 0.1 μM charybdotoxin, a K+ channel blocker.

Although proadifen prevented the BK‐caused [Ca2+]i fall, more selective cytochrome P450 inhibitors, 17‐octadecynoic acid (50 μM) and 7‐ethoxyresorufin (10 μM) were without effect.

Increasing extracellular potassium from 5 to 15 mM during angiotensin II stimulation caused a [Ca2+]i decrease (26±4%) smaller than BK which was charybdotoxin‐insensitive. Inhibition of inward rectifying K+ channels by 30 μM BaCl2 and/or of Na+/K+ ATPase by 1 mM ouabain abolished the [Ca2+]i decrease elicited by potassium but not by BK.

A voltage‐operated calcium channel blocker, nifedipine (1 μM) did not prevent the BK effect but reduced the [Ca2+]i drop.

These results indicate that the BK‐induced [Ca2+]i decrease in angiotensin II‐stimulated muscular EA is mediated by an EDHF which activates charybdotoxin‐sensitive K+ channels. In these vessels, EDHF seems to be neither a cytochrome P450‐derived arachidonic acid metabolite nor K+ itself. The closure of voltage‐operated calcium channels is not the only cellular mechanism involved in this EDHF‐mediated [Ca2+]i decrease.

British Journal of Pharmacology (2001) 132, 749–759; doi:10.1038/sj.bjp.0703851
Direct cardiac effects of intracoronary bupivacaine, levobupivacaine and ropivacaine in the sheep
Authors: Chang Dennis H‐T , Ladd Leigh A , Copeland Susan , Iglesias Miguel A , Plummer John L , Mather Laurence E
Published: January 2005

The racemic local anaesthetic agent bupivacaine is widely used clinically for its long duration of action. Levobupivacaine and ropivacaine are bupivacaine enantiopure congeners, developed to improve upon the clinical safety of bupivacaine, especially the risk of fatal arrhythmogenesis.

In previous preclinical studies of the safety of these drugs with intravenous administration in conscious ewes over a wide dose range, we found that central nervous system (CNS) excito‐toxicity reversed the cardiac depressant effects when doses approached the convulsant threshold and thus precluded accurate comparison of their cardiovascular system (CVS) effects.

To study CVS effects over a wide range of doses with minimal CNS and other influences, brief (3 min) infusions of bupivacaine, levobupivacaine or ropivacaine were administered into the left main coronary arteries of previously instrumented conscious ewes (∼50 Kg body weight). After dose‐ranging studies, the drugs were compared in a randomized, blinded, parallel group design. Equimolar doses were increased from 8 μmol (∼amp;2.5 mg) in 8 μmol increments, to either a fatal outcome or a 40 μmol (∼amp;12.5 mg) maximum.

All three drugs produced tachycardia, decreased myocardial contractility and stroke volume and widening of electrocardiographic QRS complexes. Thirteen of 19 animals died of ventricular fibrillation: four of six with bupivacaine (mean±s.e.mean actual fatal dose: 21.8±6.4 μmol), five of seven with levobupivacaine (22.9±3.5 μmol), four of six with ropivacaine (22.9±5.9 μmol). No significant differences in survival or in fatal doses between these drugs were found.

The findings suggest that ropivacaine, levobupivacaine and bupivacaine have similar intrinsic ability to cause direct fatal cardiac toxicity when administered by left intracoronary arterial infusion in conscious sheep and do not explain the differences between the drugs found with intravenous dosage.

British Journal of Pharmacology(2001)132, 649–658; doi:10.1038/sj.bjp.0703858
Angiotensin II is involved in nitric oxide synthase and cyclo‐oxygenase inhibition‐induced leukocyte‐endothelialcell interactions in vivo
Authors: Alvarez Angeles , Piqueras Laura , Bello Regina , Canet Amparo , Moreno Lucrecia , Kubes Paul , Sanz Maria‐Jesus
Published: January 2005

Chronic inhibition of nitric oxide synthase (NOS) provokes a hypertensive state which has been shown to be angiotensin II (Ang‐II) dependent. In addition to raising blood pressure, NOS inhibition also causes leukocyte adhesion. The present study was designed to define the role of Ang‐II in hypertension and in the leukocyte‐endothelial cell interactions induced by acute NOS or cyclo‐oxygenase (COX) inhibition using intravital microscopy within the rat mesenteric microcirculation.

While pretreatment with an Ang‐II AT1 receptor antagonist (losartan) reversed the prompt increase in mean arterial blood pressure (MABP) caused by indomethacin, it had no effect on the increase evoked by systemic L‐NAME administration.

Pretreatment with losartan inhibited the leukocyte rolling flux, adhesion and emigration which occurs after 60 min NOS inhibition by 83, 80 and 70% respectively, and returned leukocyte rolling velocity to basal levels.

Losartan significantly reduced the leukocyte‐endothelial cell interaction elicited by COX inhibition. In contrast, leukocyte recruitment induced by acute mast cell activation was not inhibited by losartan.

AT1 receptor blockade also prevented the drop in haemodynamic parameters such as mean red blood cell velocity (Vmean) and shear rate caused by NOS and COX inhibition.

In this study, we have demonstrated a clear role for Ang‐II in the leukocyte‐endothelial cell interactions and haemodynamic changes which arise in the absence of NO or prostacyclin (PGI2). This is of interest since leukocyte recruitment, which culminates in the vascular lesions that occur in hypertension, atherosclerosis and myocardial ischemia‐reperfusion injury, might be prevented using AT1 Ang‐II receptor antagonists.

British Journal of Pharmacology (2001) 132, 677–684; doi:10.1038/sj.bjp.0703867
Release of amines from acidified stores following accumulation by Transport‐P
Authors: Al‐Damluji S , Shen W B
Published: January 2005

Transport‐P is an uptake process for amines in peptidergic neurones of the hypothalamus. It differs from other uptake processes by its anatomical location in post‐synaptic neurones, its functional properties and by the structure of its ligands. Transport‐P accumulates amines in intracellular vesicles, derives its energy from the electrochemical proton gradient and is linked to vacuolar‐type ATPase (V‐ATPase). Transport‐P is blocked by antidepressants. We have now studied the release of amines following uptake by Transport‐P in a cell line of hypothalamic peptidergic neurones.

Release of prazosin was not inhibited by the antidepressant desipramine; as Transport‐P is blocked by desipramine, this indicated that amines are released by a mechanism which is independent of Transport‐P.

Release of prazosin was sensitive to temperature and conformed to the Arrhenius equation. Release was minimal in the range 0 – 25°C but accelerated exponentially at higher temperatures up to 33°C. The activation energy for the release of prazosin is 83.1 kJ mol−1, corresponding to a temperature quotient (Q10) value of 3.

Release was accelerated by the organic base chloroquine, the ionophore monensin, bafilomycinA1 which inhibits V‐ATPase and by increasing extracellular pH. Thus, retention of prazosin requires an intracellular proton gradient which is generated by V‐ATPase.

Fluorescence microscopy demonstrated that release of BODIPY FL prazosin was temperature dependent and was accelerated by chloroquine and monensin.

Thus, following uptake by Transport‐P, amines are accumulated in acidified intracellular stores. Their retention in peptidergic neurones requires intracellular acidity. The amines are released by a temperature‐dependent process which is resistant to antidepressants.

British Journal of Pharmacology (2001) 132, 851–860; doi:10.1038/sj.bjp.0703872
Upregulation of vasopressin V1A receptor mRNA and protein in vascular smooth muscle cells following cyclosporin A treatment
Authors: Cottet‐Maire Florence , Avdonin Pavel V , Roulet Emmanuelle , Buetler Timo M , Mermod Nicolas , Ruegg Urs T
Published: January 2005

The major side effects of the immunosuppressive drug cyclosporin A (CsA) are hypertension and nephrotoxicity. It is likely that both are caused by local vasoconstriction.

We have shown previously that 20 h treatment of rat vascular smooth muscle cells (VSMC) with therapeutically relevant CsA concentrations increased the cellular response to [Arg8]vasopressin (AVP) by increasing about 2 fold the number of vasopressin receptors.

Displacement experiments using a specific antagonist of the vasopressin V1A receptor (V1AR) showed that the vasopressin binding sites present in VSMC were exclusively receptors of the V1A subtype.

Receptor internalization studies revealed that CsA (10−6 M) did not significantly alter AVP receptor trafficking.

 V1AR mRNA was increased by CsA, as measured by quantitative polymerase chain reaction. Time‐course studies indicated that the increase in mRNA preceded cell surface expression of the receptor, as measured by hormone binding.

A direct effect of CsA on the V1AR promoter was investigated using VSMC transfected with a V1AR promoter‐luciferase reporter construct. Surprisingly, CsA did not increase, but rather slightly reduced V1AR promoter activity. This effect was independent of the cyclophilin‐calcineurin pathway.

Measurement of V1AR mRNA decay in the presence of the transcription inhibitor actinomycin D revealed that CsA increased the half‐life of V1AR mRNA about 2 fold.

In conclusion, CsA increased the response of VSMC to AVP by upregulating V1AR expression through stabilization of its mRNA. This could be a key mechanism in enhanced vascular responsiveness induced by CsA, causing both hypertension and, via renal vasoconstriction, reduced glomerular filtration.

British Journal of Pharmacology (2001) 132, 909–917; doi:10.1038/sj.bjp.0703878
Role of ETBand B2receptors in theex vivoplatelet inhibitory properties of endothelin and bradykinin in the mouse
Authors: Labonté Julie , Brochu Isabelle , Honoré Jean‐Claude , D'Orléans‐Juste Pedro
Published: January 2005

We have developed a model to study the inhibitory properties of endogenous autacoids triggered by systemically‐administered vasoactive peptides, on platelet aggregationex vivoin the mouse.

Adenosine diphosphate (ADP) (0.5 – 10 μM) induces a concentration‐dependent aggregation of platelet‐rich plasma derived from C57BL/6 mice. Intravenously‐administered endothelin‐1 (0.01 – 1 nmol kg−1), the selective ETBagonist, IRL‐1620 (0.01 – 1 nmol kg−1) or bradykinin (1 – 100 nmol kg−1) significantly reduced in a dose‐dependent fashion the ADP‐induced platelet aggregation.

The non‐selective cyclo‐oxygenase (COX) inhibitor, indomethacin, a selective COX‐2 inhibitor NS‐398 or the prostacyclin synthase inhibitor, tranylcypromine (10 mg kg−1), markedly reduced the inhibitory properties of endothelin‐1, whereas only a combination of both indomethacin, NS‐398 or tranylcypromine andL‐NAME (10 mg kg−1) were required to abolish the response to bradykinin.

An ETB‐selective antagonist (BQ‐788) or knockout of the B2receptor gene (in B2knockout mice) abolishes the platelet inhibitory properties of endothelin‐1 and bradykinin, respectively.

Our results suggest that intravenously‐administered endothelin‐1 and bradykinin, through ETBand B2receptor activation, respectively, inhibit platelet aggregationex vivoin the mouse. The inhibitory properties of endothelin‐1 require the activation of COX‐2 and the subsequent generation of prostacyclin. In addition to the two previously mentioned factors, nitric oxide is required for the anti‐aggregatory effects of bradykinin.

British Journal of Pharmacology(2001)132, 934–940; doi:10.1038/sj.bjp.0703880
α2‐Adrenoceptors modulating neuronal serotonin release: a study in α2‐adrenoceptor subtype‐deficient mice
Authors: Scheibner Jens , Trendelenburg Anne‐Ulrike , Hein Lutz , Starke Klaus
Published: January 2005

The release‐inhibiting α2‐adrenoceptors of cerebral serotoninergic axons were studied in mice. Slices of the hippocampus or the occipito‐parietal cortex from NMRI mice, from mice lacking the α2A/D‐, the α2B‐, the α2C‐ or both the α2A/D‐ and the α2C‐adrenoceptor, and from mice sharing the genetic background of the receptor‐deficient animals (WT) were preincubated with [3H]‐serotonin and then superfused and stimulated electrically, in most experiments by trains of 8 pulses at 100 Hz.

The concentration‐response curves of the α2‐adrenoceptor agonist medetomidine were virtually identical in hippocampal slices from NMRI and WT mice, with maximally 70% inhibition and an EC50 of about 2 nM. In hippocampal slices from NMRI mice, phentolamine and rauwolscine were equipotent antagonists against medetomidine.

The effect of medetomidine was greatly reduced, with maximally 20% inhibition, in hippocampal slices from α2A/D‐adrenoceptor‐deficient mice; was slightly reduced, with maximally 59% inhibition, in hippocampal slices from α2C‐adrenoceptor‐deficient mice; was not changed in hippocampal slices from α2B‐adrenoceptor‐deficient mice; and was abolished in hippocampal slices from mice lacking both the α2A/D‐ and the α2C‐adrenoceptor.

Similar results were obtained in: (i) occipito‐parietal slices from NMRI and α2A/D‐adrenoceptor‐deficient mice and (ii) hippocampal slices that were preincubated with [3H]‐serotonin in the presence of oxaprotiline to rule out cross‐labelling of noradrenergic axons.

The serotoninergic axons of the mouse brain possess both α2A/D‐heteroreceptors, which predominate, and α2C‐heteroreceptors but lack α2B‐adrenoceptors. The situation resembles the coexistence of α2A/D‐ and α2C‐autoreceptors but lack of α2B‐autoreceptors at the noradrenergic axons of mice.

British Journal of Pharmacology (2001) 132, 925–933; doi:10.1038/sj.bjp.0703882
BK channel activation by NS‐1619 is partially mediated by intracellular Ca2+ release in smooth muscle cells of porcine coronary artery
Authors: Yamamura Hisao , Ohi Yoshiaki , Muraki Katsuhiko , Watanabe Minoru , Imaizumi Yuji
Published: January 2005

Effects of NS‐1619, an opener of large conductance Ca2+‐activated K+ (BK) channel, on intracellular Ca2+ concentration ([Ca2+]i) and membrane potential were examined in single myocytes freshly isolated from porcine coronary artery.

Under current clamp mode, the application of 1 – 30 μM NS‐1619 hyperpolarized the membrane in concentration‐dependent manner. The NS‐1619‐induced hyperpolarization was abolished by the presence of 100 nM iberiotoxin.

Application of 1 – 10 μM NS‐1619 hyperpolarized the membrane by approximately 6 mV or less but did not change significantly the [Ca2+]i. When membrane hyperpolarization of 12 mV or so was caused by 30 μM NS‐1619, [Ca2+]i was unexpectedly increased by approximately 200 nM. This increase in [Ca2+]i and the concomitant outward current activation were also observed under voltage‐clamp at holding potential of −40 mV.

The increase in [Ca2+]i by 30 μM NS‐1619 occurred mainly in peripheral regions than in the centre of the myocytes. The removal of extracellular Ca2+ affected neither the membrane hyperpolarization nor the increase in [Ca2+]i.

In the presence of 10 mM caffeine and 10 μM ryanodine, the increase in [Ca2+]i by 30 μM NS‐1619 was not observed and the membrane hyperpolarization was reduced to approximately 67% of the control.

These results indicate that the opening of BK channels by NS‐1619 at 30 μM, which is the most frequently used concentration of this agent, is partly due to Ca2+ release from caffeine/ryanodine‐sensitive intracellular storage sites but is mainly due to the direct activation of the channels.

British Journal of Pharmacology (2001) 132, 828–834; doi:10.1038/sj.bjp.0703885
Pharmacological evidence for CGRP uptake into perivascular capsaicin sensitive nerve terminals
Authors: Sams‐Nielsen Anette , Orskov Cathrine , Jansen‐Olesen Inger
Published: January 2005

Specific mechanisms, providing reuptake of cathecholamine and amino acid neurotransmitters (e.g. serotonin and glutamate) into cells of the central nervous system are well known, whereas neuronal uptake of neuropeptide transmitters have not previously been reported.

In the present study we present evidence for uptake of the 37 amino acid neuropeptide, calcitonin gene‐related peptide (CGRP) into perivascular terminals of capsaicin sensitive nerve fibres, innervating the guinea‐pig basilar artery.

Release of CGRP from perivascular nerve terminals was obtained by capsaicin‐induced vanilloid receptor‐stimulation and detected as CGRP receptor‐mediated dilation of isolated segments of the guinea‐pig basilar artery.

Following three repeated capsaicin challenges, CGRP‐depleted segments were incubated with CGRP. This caused significant reappearance of capsaicin‐induced vasodilatory responses. These responses were dependent on duration and concentration of the preceding CGRP incubation and were inhibited by the CGRP receptor antagonist, CGRP8–37.

The CGRP‐re‐depletion was significantly reduced when CGRP8–37 was present during the preceding CGRP incubation. Thus, presynaptic CGRP receptors are likely to be involved in neuronal CGRP uptake.

Incubating the artery segments with 125I‐CGRP allowed subsequent detection of capsaicin‐induced 125I‐release.

Immunohistochemical experiments showed that only terminal CGRP is subject to capsaicin‐induced depletion in vitro, whereas CGRP‐immunoreactivity endures in the nerve fibres.

British Journal of Pharmacology (2001) 132, 1145–1153; doi:10.1038/sj.bjp.0703910