bluuebunny/crossref_metadata_2025_split huggingface dataset:
trans‐Resveratrol inhibits calcium influx in thrombin‐stimulated human platelets
Authors: Dobrydneva Yuliya , Williams Roy L , Blackmore Peter F 
Published: January 2005

The phytoestrogenic compound trans‐resveratrol (trans‐3,5,4′‐trihydroxystilbene) is found in appreciable quantities in grape skins and wine. It has been shown that both products rich in trans‐resveratrol and pure trans‐resveratrol inhibit platelet aggregation both in vivo and in vitro. However the mechanism of this action still remains unknown.
An essential component of the aggregation process in platelets is an increase in intracellular free Ca2+ ([Ca2+]i). Ca2+ must enter the cell from the external media through specific and tightly regulated Ca2+ channels in the plasma membrane. The objective of this study was to characterize what effect trans‐resveratrol had on the Ca2+ channels in thrombin stimulated platelets.
In this study we showed that trans‐resveratrol immediately inhibited Ca2+ influx in thrombin‐stimulated platelets with an IC50 of 0.5 μM. trans‐Resveratrol at 0.1, 1.0 and 10.0 μM produced 20±6, 37±6 and 57±4% inhibition respectively of the effect of thrombin (0.01 u  ml−1) to increase [Ca2+]i.
trans‐Resveratrol also inhibited spontaneous Ba2+ entry into Fura‐2 loaded platelets, with 0.1, 1.0 and 10.0 μM trans‐resveratrol producing 10±5, 30±5 and 50±7% inhibition respectively. This indicated that trans‐resveratrol directly inhibited Ca2+ channel activity in the platelets in the absence of agonist stimulation.
trans‐Resveratrol also inhibited thapsigargin‐mediated Ca2+ influx into platelets. This suggests that the store‐operated Ca2+ channels are one of the possible targets of trans‐resveratrol. These channels rely on the emptying of the internal Ca2+ stores to initiate influx of Ca2+ into the cell.
The phytoestrogens genistein, daidzein, apigenin and genistein‐glucoside (genistin) produced inhibitory effects against thrombin similar to those seen with trans‐resveratrol.
We conclude that trans‐resveratrol is an inhibitor of store‐operated Ca2+ channels in human platelets. This accounts for the ability of trans‐resveratrol to inhibit platelet aggregation induced by thrombin.

British Journal of Pharmacology (1999) 128, 149–157; doi:10.1038/sj.bjp.0702749
Selective β1‐adrenoceptor blockade enhances the activity of the stimulatory G‐protein in human atrial myocardium
Authors: Wang Tao , Plumpton Christopher , Brown Morris J 
Published: January 2005

Chronic selective β1‐adrenoceptor (β1AR) blocker treatment enhances the sensitivity of β2‐adrenoceptor (β2AR) in human heart (Hall et al., 1990; 1991). To clarify the mechanism of the cross‐sensitization between β1AR and β2AR, we determined whether the stimulatory G‐protein (Gsα) function is increased in atria from β1AR‐blocker treated patients compared with non‐β‐blocked patients, and investigated whether this change is caused by an alteration of post‐translational modification of Gsα protein.
Gsα function was determined by reconstitution of human atrial Gsα into S49 cyc− cell membranes. In the reconstitution system, GTPγS stimulated cyclic AMP generation in a dose‐dependent manner. Upon 10−4 M GTPγS stimulation, Gsα activity in the β1AR‐blocker, atenolol, treated group (78.2±10.3 pmol cyclic AMP mg−1 min−1 10−3) was 65% higher than that in non‐β‐blocked patients (47.3±6.3 pmol cyclic AMP mg−1 min−1 10−3, n=15, P=0.02).
Isoelectric point (pI) values of Gsα were measured by two dimensional gel electrophoresis (2D‐E) and the amount of each isoform quantified by image analysis of a Western blot of the gel using specific antibody. Multiple isoforms of Gsα were detected by 2D‐E with different pI values. There were no significant differences between the groups of patients in either pI values or the proportions of the acidic isoforms of Gsα to the main basic form (n=12, P>0.05).
The results suggest that chronic β1AR‐blockade enhances Gsα function in human atrium, and this may account in part for the hypersensitivity of β2AR and other Gs‐coupled receptors during β1AR‐blockade. The increased Gsα function is unlikely to be caused directly by blockade of protein kinase A phosphorylation of Gsα protein.

British Journal of Pharmacology (1999) 128, 135–141; doi:10.1038/sj.bjp.0702750
Modulation by protease‐activated receptors of the rat duodenal motility in vitro: possible mechanisms underlying the evoked contraction and relaxation
Authors: Kawabata Atsufumi , Kuroda Ryotaro , Nishikawa Hiroyuki , Kawai Kenzo 
Published: January 2005

The present study examined effects of agonist enzymes and receptor‐activating peptides for protease‐activated receptors (PARs) on duodenal motility in the rat, and also investigated possible mechanisms underlying the evoked responses.
Thrombin at 0.03–0.1 μM and the PAR‐1‐activating peptide SFLLR‐NH2 at 3–100 μM or TFLLR‐NH2 at 10–50 μM produced a dual action, relaxation followed by contraction of the duodenal longitudinal muscle. The PAR‐2‐activating peptide SLIGRL‐NH2 at 10–100 μM elicited only small contraction. Trypsin at 0.08 μM induced small contraction, or relaxation followed by contraction, depending on preparations. The PAR‐4‐activating peptide GYPGKF‐NH2 at 1000 μM exhibited no effect.
The contractile responses of the duodenal strips to TFLLR‐NH2 and to SLIGRL‐NH2 were partially attenuated by the L‐type calcium channel blocker nifedipine (1 μM), the protein kinase C inhibitor GF109203X (1 μM) and the tyrosine kinase inhibitor genistein (15 μM), but were resistant to indomethacin (3 μM) and tetrodotoxin (1–10 μM).
The relaxation of the preparations exerted by TFLLR‐NH2 was unaffected by indomethacin (3 μM), propranolol (5 μM), NG‐nitro‐L‐arginine methyl ester (100 μM) and tetrodotoxin (1–10 μM). This relaxation was resistant to either GF109203X (1 μM) or genistein (15 μM), but was, remarkably, attenuated by combined application of these two kinase inhibitors.
Apamin (0.1 μM), an inhibitor of calcium‐activated, small‐conductance potassium channels, but not charybdotoxin (0.1 μM), completely abolished the PAR‐1‐mediated duodenal relaxation, and significantly enhanced the PAR‐1‐mediated contraction.
These findings demonstrate that PAR‐1 plays a dual role, suppression and facilitation of smooth muscle motility in the rat duodenum, while PAR‐2 plays a minor excitatory role in the muscle, and that PAR‐4 is not involved in the duodenal tension modulation. The results also suggest that the contractile responses to PAR‐1 and PAR‐2 activation are mediated, in part, by activation of L‐type calcium channels, protein kinase C and tyrosine kinase, and that the relaxation response to PAR‐1 activation occurs via activation of apamin‐sensitive, but charybdotoxin‐insensitive, potassium channels, in which both protein kinase C and tyrosine kinase might be involved synergistically.

British Journal of Pharmacology (1999) 128, 865–872; doi:10.1038/sj.bjp.0702755
The cannabinoid CB1 receptor antagonist, SR141716A, selectively facilitates nociceptive responses of dorsal horn neurones in the rat
Authors: Chapman Victoria 
Published: January 2005

The effect of spinal administration of the selective cannabinoid CB1 receptor antagonist, SR141716A, and the selective CB2 receptor antagonist, SR144528, on innocuous versus noxious evoked responses of dorsal horn neurones in the spinal cord of the anaesthetized rat was investigated. SR141716A (0.001–1 ng 50 μl−1) dose‐relatedly facilitated the non‐potentiated component of the electrical C‐fibre mediated neuronal response (120±6, 156±13, 192±33 and 192±31% of control respectively; n=6). In contrast, SR144528 (0.001–1 ng 50 μl−1) did not influence the non‐potentiated component of the C‐fibre evoked neuronal response (n=5). The electrical evoked Aβ‐fibre mediated neuronal responses were not influenced by SR141716A or SR144528. The results of this study provide evidence that tonic cannabinoid CB1 receptor activation, but not CB2 receptor activation, attenuates acute nociceptive transmission, at the level of the spinal cord. These results suggest a selective antinociceptive role of the endogenous cannabinoids at spinal CB1 receptors.British Journal of Pharmacology (1999) 127, 1765–1767; doi:10.1038/sj.bjp.0702758
5‐CT stimulation of adenylyl cyclase activity in guinea‐pig hippocampus: evidence for involvement of 5‐HT7 and 5‐HT1A receptors
Authors: Thomas David R , Middlemiss Derek N , Taylor Stephen G , Nelson Paul , Brown Anthony M 
Published: January 2005

A number of compounds, including the selective 5‐HT7 receptor antagonist SB‐258719, were investigated for their effect on [3H]‐5‐carboxamidotryptamine (5‐CT) radioligand binding and 5‐CT‐stimulated adenylyl cyclase activity in guinea‐pig hippocampal membranes, in order to confirm the presence of functionally coupled 5‐HT7 receptors in this tissue.
The [3H]‐5‐CT radioligand binding profile was consistent with binding predominantly to 5‐HT7 receptors. The affinity of SB‐258719 (pKi 7.2±0.1) was similar to its reported human 5‐HT7 receptor affinity.
In the adenylyl cyclase functional assay, 5‐CT was a potent and full agonist compared to 5‐HT, whereas 8‐hydroxy‐dipropylaminotetralin (8‐OH‐DPAT) was a partial agonist (intrinsic activity 0.4±0.1). The rank order of potency for agonists (5‐CT>5‐HT∼8‐OH‐DPAT) was consistent with activation of 5‐HT7 receptors. SB‐258719 (5  μM) and methiothepin (1 μM) surmountably antagonized the response to 5‐CT, consistent with competitive antagonism. The pKB for SB‐258719 (7.2±0.1) was in good agreement with its reported antagonist potency at the human cloned 5‐HT7 receptor.
In the functional assay, WAY‐100635 (100 nM) and cyanopindolol (1 μM) induced a biphasic 5‐CT response curve, consistent with selective antagonism of a component of the response to 5‐CT. The estimated pKB values for WAY‐100635 and cyanopindolol (9.6 and 8.4 respectively) were in good agreement with their reported 5‐HT1A receptor affinities.
The data are consistent with the presence of 5‐HT7 receptors in guinea‐pig hippocampus which are positively coupled to adenylyl cyclase. In addition, 5‐HT7 receptor‐mediated stimulation of adenylyl cyclase activity in this tissue appears to be augmented by a mechanism involving 5‐HT1A receptor activation.

British Journal of Pharmacology (1999) 128, 158–164; doi:10.1038/sj.bjp.0702759
Modulatory effects of adenosine on inhibitory postsynaptic potentials in the lateral amygdala of the rat
Authors: Heinbockel Thomas , Pape Hans‐Christian 
Published: January 2005

Adenosine is a depressant in the central nervous system with pre‐ and postsynaptic effects. In the present study, intracellular recording techniques were applied to investigate the modulatory effects of adenosine on projection neurons in the lateral rat amygdala (LA), maintained as slices in vitro.
Adenosine reversibly reduced the amplitude of a fast inhibitory postsynaptic potential (IPSP) that was evoked by electrical stimulation of the external capsule and pharmacologically isolated by applying an N‐methyl‐D‐aspartate and non‐N‐methyl‐D‐aspartate receptor antagonist, DL‐(−)‐2‐amino‐5‐methyl‐4‐isoxazolepropionic acid and 6,7‐Dinitroquinoxaline‐2,3‐dione, respectively, and the γ‐aminobutyric acidB (GABAB) receptor antagonist CGP 35348. The postsynaptic potential that remained was abolished by locally applying bicuculline.
Adenosine reduced the amplitude of the fast IPSP on average by 40.3%. It had no significant effect on responses to exogenously applied GABA, on membrane potential or on input resistance, suggesting that the site of action was at presynaptic inhibitory interneurons in the LA.
The response to adenosine was mimicked by the selective adenosine A1 receptor agonist N6‐cyclohexyladenosine and blocked by the selective adenosine A1 receptor antagonist 8‐cyclopentyl‐1,3‐dipropylxanthine.
Neuronal responsiveness in the amygdala is largely controlled by inhibitory processes. Adenosine can presynaptically downregulate inhibitory postsynaptic responses and could exert dampening effects likely by depression of both excitatory and inhibitory neurotransmitter release.

British Journal of Pharmacology (1999) 128, 190–196; doi:10.1038/sj.bjp.0702761
Structural requirements of sulphonylureas and analogues for interaction with sulphonylurea receptor subtypes
Authors: Meyer Miriam , Chudziak Franz , Schwanstecher Christina , Schwanstecher Mathias , Panten Uwe 
Published: January 2005

The structure‐activity relationship for hypoglycaemic sulphonylureas and analogues was examined. Binding affinities were compared using membranes from HIT‐T15 cells (β‐cell line) and from COS‐7 cells transiently expressing sulphonylurea receptor subtypes (SUR1, SUR2A and SUR2B). Inhibition of adenosine‐triphosphate‐sensitive K+ channels (KATP‐channels) was measured in mouse pancreatic β‐cells.
The tested compounds displayed similar binding affinities for SUR2A and SUR2B.
Meglitinide (benzoic acid derivative) bound to SUR1 and the SUR2 isoforms with similar affinities. Replacement of the carboxyl group of meglitinide by a methyl group significantly decreased the binding affinities for SUR1 and the SUR2 isoforms (>4 fold) and the potency to inhibit KATP‐channel activity of β‐cells (24 fold). Replacement of the carboxyl group of meglitinide by a sulphonylurea group significantly increased the affinities for SUR1 (5 fold) and the SUR2 isoforms (13–16 fold).
Glibenclamide bound to the SUR2 isoforms with 300–500 fold lower affinity than to SUR1. Exchanging the cyclohexyl ring of glibenclamide by a methyl group or removal of the lipophilic side chain of glibenclamide (5‐chloro‐2‐methoxy‐benzamidoethyl chain) markedly reduced but did not abolish the selectivity for SUR1.
In conclusion, interaction of sulphonylureas and acidic analogues with SUR1, SUR2A and SUR2B is favoured by the anionic group of these drugs. Hypoglycaemic sulphonylureas (e.g. glibenclamide) owe selectivity for SUR1 to lipophilic substitution on their urea group. Sulphonylureas without lipophilic substitution on the urea group could represent lead compounds for the development of SUR2‐selective drugs.

British Journal of Pharmacology (1999) 128, 27–34; doi:10.1038/sj.bjp.0702763
Receptors mediating CGRP‐induced relaxation in the rat isolated thoracic aorta and porcine isolated coronary artery differentiated by hα CGRP8–37
Authors: Wisskirchen F M , Gray D W , Marshall I 
Published: January 2005

Receptors mediating CGRP‐induced vasorelaxation were investigated in rat thoracic aorta and porcine left anterior descending (LAD) coronary artery and anterior interventricular artery (AIA), using CGRP agonists, homologues and the antagonist hα CGRP8–37.
In the endothelium‐intact rat aorta, hα CGRP, hβ CGRP, rat β CGRP and human adrenomedullin caused relaxation with similar potencies. Compared with hα CGRP, rat amylin was about 25 fold less potent, while [Cys(ACM2,7)] hα CGRP and salmon calcitonin were at least 1000 fold weaker.
Hα CGRP8–37 (up to 10−5 M) did not antagonize responses to hα CGRP, hβ CGRP or rat β CGRP (apparent pKB <5). Peptidase inhibitors did not increase either the effect of hα CGRP or [Cys(ACM,2,7)] hα CGRP, while hα CGRP8–37 remained inactive. Endothelium‐dependent relaxation produced by hα CGRP was accompanied by increases in cyclic AMP and cyclic GMP, that were not inhibited by hα CGRP8–37 (10−5 M).
In porcine LAD and AIA, hα CGRP produced relaxation in an endothelium‐independent manner. Hα CGRP8‐37 competitively antagonized hα CGRP responses (pA2 6.3 and 6.7 (Schild slope 0.9±0.1, each), in LAD and AIA, respectively). In LAD artery, hα CGRP‐induced relaxation was accompanied by increases in cyclic AMP that were inhibited by hα CGRP8–37 (10−7–10−5 M).
In conclusion, the antagonist affinity for hα CGRP8–37 in porcine coronary artery is consistent with a CGRP1 receptor, while the lack of hα CGRP8–37 antagonism in rat aorta could suggest either a CGRP receptor different from CGRP1 and CGRP2 type, or a non‐CGRP receptor.

British Journal of Pharmacology (1999) 128, 283–292; doi:10.1038/sj.bjp.0702764
Alteration of glycogen and glucose metabolism in ischaemic and post‐ischaemic working rat hearts by adenosine A1 receptor stimulation
Authors: Fraser Heather , Lopaschuk Gary D , Clanachan Alexander S 
Published: January 2005

Cardioprotection by adenosine A1 receptor activation limits infarct size and improves post‐ischaemic mechanical function. The mechanisms responsible are unclear but may involve alterations in myocardial glucose metabolism.
Since glycogen is an important source of glucose during ischaemia, we examined the effects of N6‐cyclohexyladenosine (CHA), an A1 receptor agonist, on glycogen and glucose metabolism during ischaemia as well as reperfusion.
Isolated working rat hearts were perfused with Krebs‐Henseleit solution containing dual‐labelled 5‐3H and 14C glucose and palmitate as energy substrates. Rates of glycolysis and glucose oxidation were measured directly from the production of 3H2O and 14CO2. Glycogen turnover was measured from the rate of change of [5‐3H and 14C]glucosyl units in total myocardial glycogen.
Following low‐flow (0.5 ml min−1) ischaemia (60 min) and reperfusion (30 min), left ventricular minute work (LV work) recovered to 22% of pre‐ischaemic values. CHA (0.5 μM) improved the recovery of LV work 2 fold.
CHA altered glycogen turnover in post‐ischaemic hearts by stimulating glycogen synthesis while having no effects on glycogen degradation. CHA also partially inhibited glycolysis. These changes accelerated the recovery of glycogen in CHA‐treated hearts and reduced proton production.
During ischaemia, CHA had no measurable effect on glycogen turnover or glucose metabolism. Glycogen phosphorylase activity, which was elevated after ischaemia, was inhibited by CHA, possibly in response to CHA‐induced inhibition of AMP‐activated protein kinase activity.
These results indicate that CHA‐induced cardioprotection is associated with alterations of glycogen turnover during reperfusion as well as improved metabolic coupling of glycolysis to glucose oxidation.

British Journal of Pharmacology (1999) 128, 197–205; doi:10.1038/sj.bjp.0702765
Interleukin‐1β (IL‐1β) inhibition: a possible mechanism for the anti‐inflammatory potency of liposomally conjugated methotrexate formulations in arthritis
Authors: Williams A S , Jones S G , Goodfellow R M , Amos N , Williams B D 
Published: January 2005

Liposomes with conventional and long‐circulation times were employed as carriers for the methotrexate derivative MTX‐γ‐DMPE (MTX‐EPC and MTX‐PEG respectively), their mechanism of action was investigated in vitro and in vivo and their therapeutic efficacy assessed using the rat collagen‐induced arthritis (CIA) model.
At non‐toxic dose, both MTX‐EPC and MTX‐PEG inhibited the lipopolysaccharide (LPS) induced release of IL‐1β from activated rat peritoneal macrophages (rPMΦ) in a dose and time dependent manner. Free methotrexate (MTX) was not active in this respect. After a single intravenous injection (i.v.), and at equivalent doses, both free MTX (500 μg) and MTX‐EPC inhibited the LPS induced rise in plasma IL‐1β levels observed in MTX‐PEG and saline treated rats.
When used to treat established CIA, MTX‐EPC resulted in significantly lower clinical score (CS) (1.0±0.42 (P<0.001)) and hind paw diameter (HPD) (6.5±0.34 mm (P<0.001)) measurements than controls (3.0±0.26; 7.33±0.41 mm), after only two i.v. doses, and remained significantly lower for the entire experimental period. By day 24 both CS (2±0.61 (P<0.001)) and HPD (6.97±0.25 mm (P<0.002)) measurements had also become significantly lower in MTX‐PEG treated rats than in saline treated controls (3.62±0.17, 7.92±0.38 mm) and remained lower until day 30. Joint inflammation in MTX treated rats was completely ameliorated by day 20 but the health and well being of the animals was compromised and the experiment terminated at this time‐point.
Our results clearly demonstrate that both MTX‐EPC and MTX‐PEG liposomes have potential for development into therapeutic modalities for the treatment of inflammatory joint disease in man.

British Journal of Pharmacology (1999) 128, 234–240; doi:10.1038/sj.bjp.0702776
Inadequate ischaemia‐selectivity limits the antiarrhythmic efficacy of mibefradil during regional ischaemia and reperfusion in the rat isolated perfused heart
Authors: Farkas András , Qureshi Aasim , Curtis Michael J 
Published: January 2005

Mibefradil was compared with (±)‐verapamil for effects on ischaemia‐ and reperfusion‐induced ventricular fibrillation (VF), and the role of ischaemia‐selective L‐channel block was examined. Langendorff perfused rat hearts (n=12/group) were used.
Neither drug at up to 100 nM reduced the incidence of VF during 30 min regional ischaemia. 300 and 600 nM (±)‐verapamil abolished VF (P<0.05); mibefradil was effective only at 600 nM (P<0.05). Reperfusion‐induced VF incidence was reduced only by 600 nM (±)‐verapamil (P<0.05). Both drugs at 100 nM increased coronary flow (P<0.05) with a similar potency and maximum effectiveness.
In separate hearts perfused with Krebs' solution containing 3 mM K+ (the same as that used for arrhythmia studies) neither drug at up to 600 nM affected ventricular contractility. With K+ raised to 6 mM, (±)‐verapamil 30 nM reduced developed pressure (P<0.05); mibefradil did so only at 600 nM (P<0.05). With K+ raised to 10 mM the effects of (±)‐verapamil were further increased (P<0.05) and mibefradil became active at 100 nM (P<0.05). Likewise both drugs impaired diastolic relaxation, with raised K+ exacerbating the effects and (±)‐verapamil being more potent and its effects more greatly exacerbated by K+. In contrast, when K+ was normal (3 mM), coronary flow was increased by each drug at 30 nM (P<0.05) indicating a marked vascular : myocardial selectivity.
In conclusion, mibefradil differed from (±)‐verapamil in its myocardial effects only in terms of its lower potency. As mibefradil is the more potent T‐channel blocker, the T‐channel is unlikely to represent the molecular target for these effects. The K+ elevations that occur in the ischaemic milieu determine the ability of both drugs to block myocardial L‐channels; this is sufficient to account for the drugs' actions on VF. Neither drug possesses sufficient selectivity for ischaemic myocardium versus blood vessels to permit efficacy (VF suppression without marked vasodilatation) and so inappropriate hypotension is likely to preclude the safe use of mibefradil (or similar analogue) in VF suppression, and explains the lack of clinical effectiveness of (±)‐verapamil.

British Journal of Pharmacology (1999) 128, 41–50; doi:10.1038/sj.bjp.0702778