bluuebunny/crossref_metadata_2025 huggingface dataset:
Chronic morphine induces up‐regulation of the pro‐apoptotic Fas receptor and down‐regulation of the anti‐apoptotic Bcl‐2 oncoprotein in rat brain
Authors: Boronat M Assumpció , García‐Fuster M Julia , García‐Sevilla Jesús A
Published: January 2005

This study was designed to assess the influence of activation and blockade of the endogenous opioid system in the brain on two key proteins involved in the regulation of programmed cell death: the pro‐apoptotic Fas receptor and the anti‐apoptotic Bcl‐2 oncoprotein.

The acute treatment of rats with the μ‐opioid receptor agonist morphine (3 – 30 mg kg−1, i.p., 2 h) did not modify the immunodensity of Fas or Bcl‐2 proteins in the cerebral cortex. Similarly, the acute treatment with low and high doses of the antagonist naloxone (1 and 100 mg kg−1, i.p., 2 h) did not alter Fas or Bcl‐2 protein expression in brain cortex. These results discounted a tonic regulation through opioid receptors on Fas and Bcl‐2 proteins in rat brain.

Chronic morphine (10 – 100 mg kg−1, 5 days, and 10 mg kg−1, 13 days) induced marked increases (47 – 123%) in the immunodensity of Fas receptor in the cerebral cortex. In contrast, chronic morphine (5 and 13 days) decreased the immunodensity of Bcl‐2 protein (15 – 30%) in brain cortex. Chronic naloxone (10 mg kg−1, 13 days) did not alter the immunodensities of Fas and Bcl‐2 proteins in the cerebral cortex.

The concurrent chronic treatment (13 days) of naloxone (10 mg kg−1) and morphine (10 mg kg−1) completely prevented the morphine‐induced increase in Fas receptor and decrease in Bcl‐2 protein immunoreactivities in the cerebral cortex.

The results indicate that morphine, through the sustained activation of opioid receptors, can promote abnormal programmed cell death by enhancing the expression of pro‐apoptotic Fas receptor protein and damping the expression of anti‐apoptotic Bcl‐2 oncoprotein.

British Journal of Pharmacology (2001) 134, 1263–1270; doi:10.1038/sj.bjp.0704364
COX‐2 and cancer: a new approach to an old problem
Authors: Bakhle Y S
Published: January 2005

British Journal of Pharmacology (2001) 134, 1137–1150; doi:10.1038/sj.bjp.0704365
Increased rigidity of the chiral centre of tocainide favours stereoselectivity and use‐dependent block of skeletal muscle Na+ channels enhancing the antimyotonic activity in vivo
Authors: Talon Sophie , De Luca Annamaria , De Bellis Michela , Desaphy Jean‐François , Lentini Giovanni , Scilimati Antonio , Corbo Filomena , Franchini Carlo , Tortorella Paolo , Jockusch Harald , Conte Camerino Diana
Published: January 2005

Searching for the structural requirements improving the potency and the stereoselectivity of Na+ channel blockers as antimyotonic agents, new derivatives of tocainide, in which the chiral carbon atom is constrained in a rigid α‐proline or pyrrolo‐imidazolic cycle, were synthesized as pure enantiomers.

Their ability to block Na+ currents, elicited from −100 to −20 mV at 0.3 Hz (tonic block) and 2 – 10 Hz (use‐dependent block) frequencies, was investigated in vitro on single fibres of frog semitendinosus muscle using the vaseline‐gap voltage‐clamp method.

The α‐proline derivative, To5, was 5 and 21 fold more potent than tocainide in producing tonic and 10 Hz‐use‐dependent block, respectively. Compared to To5, the presence of one methyl group on the aminic (To6) or amidic (To7) nitrogen atom decreased use‐dependence by 2‐ and 6‐times, respectively. When methylene moieties were present on both nitrogen atoms (To8), both tonic and use‐dependent block were reduced.

Contrarily to tocainide, all proline derivatives were stereoselective in relation to an increased rigidity. A further increase in the molecular rigidity as in pyrrolo‐imidazolic derivatives markedly decreased the drug potency with respect to tocainide.

Antimyotonic activity, evaluated as the shortening of the time of righting reflexes of myotonic adr/adr mice upon acute drug in vivo administration was 3 fold more effective for R‐To5 than for R‐Tocainide.

Thus, constraining the chiral centre of tocainide in α‐proline cycle leads to more potent and stereoselective use‐dependent Na+ channel blockers with improved therapeutic potential.

British Journal of Pharmacology (2001) 134, 1523–1531; doi:10.1038/sj.bjp.0704366
Regulation of VEGF‐induced endothelial cell PAF synthesis: role of p42/44 MAPK, p38 MAPK and PI3K pathways
Authors: Bernatchez Pascal N , Allen Bruce G , Gélinas David S , Guillemette Gaétan , Sirois Martin G
Published: January 2005

Vascular endothelial growth factor (VEGF) is a potent angiogenic and inflammatory mediator. We have recently shown that this latter effect requires the activation of Flk‐1 receptor and subsequent endothelial cell (EC) PAF synthesis. However, the intracellular events that regulate EC PAF synthesis upon Flk‐1 stimulation by VEGF remain to be elucidated.

Using specific inhibitors and Western blot analysis, we herein report that in bovine aortic endothelial cells (BAEC), VEGF induces the synthesis of PAF through the cascade activation of Flk‐1 receptor, phospholipase Cγ (PLCγ), protein kinase C (PKC) and p42/44 mitogen‐activated protein kinases (MAPK).

Moreover, we demonstrate that VEGF‐mediated PAF synthesis requires the activation of p38 MAPK, likely by directing the conversion of lyso‐PAF to PAF.

Interestingly, we observed that VEGF also promoted the activation of the phosphatidyl inositol‐3‐phosphate kinase (PI3K) pathway, and that its blockade potentiated PAF synthesis following a VEGF treatment. Consequently, it appears that the PI3K pathway acts as a negative regulator of EC PAF synthesis.

Taken together, these results allow a better understanding of the intracellular events activated upon EC stimulation by VEGF, and shed a new light on the mechanisms by which VEGF induces PAF synthesis.

British Journal of Pharmacology (2001) 134, 1253–1262; doi:10.1038/sj.bjp.0704367
Impairment of myocardial contractility by anticancer anthracyclines: role of secondary alcohol metabolites and evidence of reduced toxicity by a novel disaccharide analogue
Authors: Minotti Giorgio , Parlani Massimo , Salvatorelli Emanuela , Menna Pierantonio , Cipollone Amalia , Animati Fabio , Maggi Carlo A , Manzini Stefano
Published: January 2005

The anticancer anthracycline doxorubicin (DOX) causes cardiotoxicity. Enzymatic reduction of a side chain carbonyl group converts DOX to a secondary alcohol metabolite that has been implicated in cardiotoxicity. We therefore monitored negative inotropism, assessed as inhibition of post‐rest contractions, in rat right ventricle strips exposed to DOX or to analogues forming fewer amounts of their alcohol metabolites (epirubicin, EPI, and the novel disaccharide anthracycline MEN 10755).

Thirty μM EPI exhibited higher uptake than equimolar DOX, but formed comparable amounts of alcohol metabolite due to its resistance to carbonyl reduction. MEN 10755 exhibited also an impaired uptake, and consequently formed the lowest levels of alcohol metabolite. Accordingly, DOX and EPI inhibited post‐rest contractions by ∼40 – 50%, whereas MEN 10755 inhibited by ∼6%.

One hundred μM EPI exhibited the same uptake as equimolar DOX, but formed ∼50% less alcohol metabolite. One hundred μM MEN 10755 still exhibited the lowest uptake, forming ∼60% less alcohol metabolite than EPI. Under these conditions DOX inhibited post‐rest contractions by 88%. EPI and MEN 10755 were ∼18% (P<0.05) or ∼80% (P<0.001) less inhibitory than DOX, respectively.

The negative inotropism of 30 – 100 μM DOX, EPI, or MEN 10755 correlated with cellular levels of both alcohol metabolites (r=0.88, P<0.0001) and carbonyl anthracyclines (r=0.79, P<0.0001). Nonetheless, multiple comparisons showed that alcohol metabolites were ∼20 – 40 times more effective than carbonyl anthracyclines in inhibiting contractility. The negative inotropism of MEN 10755 was therefore increased by chemical procedures, like side chain valeryl esterification, that facilitated its uptake and conversion to alcohol metabolite but not its retention in a carbonyl form.

These results demonstrate that secondary alcohol metabolites are important mediators of cardiotoxicity. A combination of reduced uptake and limited conversion to alcohol metabolite formation might therefore render MEN 10755 more cardiac tolerable than DOX and EPI.

British Journal of Pharmacology (2001) 134, 1271–1278; doi:10.1038/sj.bjp.0704369
N‐[3,4‐dimethoxycinnamoyl]‐anthranilic acid (tranilast) suppresses microglial inducible nitric oxide synthase (iNOS) expression and activity induced by interferon‐γ (IFN‐γ)
Authors: Platten Michael , Wick Wolfgang , Wischhusen Jörg , Weller Michael
Published: January 2005

Microglial cells up‐regulate inducible nitric oxide synthase (iNOS) expression in response to various pro‐inflammatory stimuli including interferon‐γ (IFN‐γ), allowing for the release of nitric oxide (NO). Tranilast (N‐[3,4‐dimethoxycinnamoyl]‐anthranilic acid) is an antiallergic compound with suppressive effects on the activation of monocytes.

Here, we show that N9 murine microglial cells express iNOS mRNA and protein and release nitric oxide into the culture medium in response to IFN‐γ (200 u ml−1) as measured by Northern and Western blot analyses and Griess assay.

Exposure to non‐toxic doses of tranilast (30 – 300 μM) leads to a concentration‐dependent inhibition of IFN‐γ‐induced (200 u ml−1) iNOS mRNA and protein expression. This is paralleled by a suppression of NO‐release into the cell culture medium.

Inhibition of IFN‐γ‐induced iNOS mRNA expression by tranilast is paralleled by an inhibition of nuclear factor‐κB (NF‐κB) activation and phosphorylation of inhibitory κB (IκB) as determined by Western blot analyses and NF‐κB reporter gene assay.

These results suggest that tranilast‐mediated suppression of microglial iNOS activity induced by IFN‐γ involves the inhibition of NF‐κB‐dependent iNOS mRNA expression.

British Journal of Pharmacology (2001) 134, 1279–1284; doi:10.1038/sj.bjp.0704373
Changes in blood glucose and plasma insulin levels induced by bradykinin in anaesthetized rats
Authors: Damas Jacques , Hallet Claude , Lefebvre Pierre J
Published: January 2005

The influence of bradykinin (BK) on blood glucose and plasma insulin levels was investigated in anaesthetized rats.

Blood glucose level was dose‐dependently increased by intravenous infusion of BK. This effect of BK was enhanced by captopril, an inhibitor of angiotensin‐converting enzyme (ACE). Des‐Arg9‐bradykinin (DABK), a kinin B1 receptor agonist, did not modify blood glucose levels while the effect of BK was inhibited by Hoe‐140, a kinin B2 receptor antagonist. The effect of BK was reduced by the NO‐synthase inhibitor, Nω‐nitro‐L‐arginine methyl ester (L‐NAME), and by the cyclo‐oxygenase inhibitor, indomethacin.

The effect of BK was suppressed by the association of propranolol with phentolamine or phenoxybenzamine. It was also reduced by hexamethonium, a ganglion‐blocking drug. In adrenalectomized rats, the infusion of BK slightly decreased blood glucose levels.

The hyperglycaemic effect of adrenaline was suppressed by propranolol associated with phentolamine or phenoxybenzamine, but it was not modified by L‐NAME.

Infusion of BK did not modify plasma insulin levels. However, after phentolamine and propranolol, BK induced a transient 2 fold rise in plasma insulin levels. The release of insulin was dose‐dependent and inhibited by Hoe‐140.

We conclude that infusion of BK induces, via a stimulation of B2 receptors, the release of NO and of prostanoids. The latter agents activate through a reflex pathway the release of catecholamines from the adrenal medulla. This release increases blood glucose levels and reduces plasma insulin levels. After adrenoceptor inhibition, BK induces a secretion of insulin, via the stimulation of B2 receptors.

British Journal of Pharmacology (2001) 134, 1312–1318; doi:10.1038/sj.bjp.0704374
Effects of carbamazepine on the first ovulation in gonadotropin‐primed immature female rats
Authors: Tamura Kazuhiro , Yatabe Yoriko , Sakamoto Hajime , Hosokawa Masakiyo , Kobayashi Kaoru , Chiba Kan , Kogo Hiroshi
Published: January 2005

The effects of carbamazepine (CBZ) and its possible mechanisms on the first ovulation were investigated in immature female rats. The first ovulation was induced by administration of equine chorionic gonadotropin (eCG) at 0800 h at 26 days of age.

A single s.c. injection of 360 mg kg−1 CBZ at 1300 h on the first pro‐oestrus (day 28) completely inhibited the first ovulation on the morning of day 29. A marked elevation in 13, 14‐dihydro‐prostaglandin F2α (13, 14H2‐PGF2α) forming capacity, a sensitive indicator of luteinizing hormone (LH) surge, was not detected in the CBZ‐treated group at 0800 h on day 29 (72 h after eCG treatment). The elevation in serum LH levels at 57 h after eCG treatment was not observed in the CBZ‐treated group, either. The blocking of the first ovulation and 13, 14H2‐PGF2α forming capacity were recovered by an i.p. injection of human CG on day 28 in all animals.

However, the first ovulation was not blocked by repeated injections of 360 mg kg−1 CBZ at 1300 h once daily for 3 days (days 26 – 28). The repeated injections of CBZ caused a great fall (64% decrease) in the serum levels of CBZ at 4 h after the final CBZ injection as compared with the case of a single injection of CBZ and resulted in a delay for 5 h the occurrence of LH surge, which is normally observed around 57 h after eCG injection.

A significant increase in the activity of microsomal CBZ catabolism by the repeated injections of CBZ was quantitatively verified by the HPLC analysis. But, the activity of CBZ metabolism in the single injected‐animals showed almost similar levels to that in the control.

The present results demonstrated that a single injection of CBZ blocks the ovulation by inhibiting LH surge but that the failure of the inhibition of ovulation by repeated injections of CBZ is due to a decrease in serum CBZ levels mediated through CBZ‐induced hepatic enzyme induction.

British Journal of Pharmacology (2001) 134, 1328–1334; doi:10.1038/sj.bjp.0704375
Ginsenosides Rb1 and Re decrease cardiac contraction in adult rat ventricular myocytes: role of nitric oxide
Authors: Scott Glenda I , Colligan Peter B , Ren Bonnie H , Ren Jun
Published: January 2005

Panax ginseng is used to enhance stamina and relieve fatigue as well as physical stress. Ginsenoside, the effective component of ginseng, regulates cardiovascular function. This study was to examine the effect of ginsenosides Rb1 and Re on cardiac contractile function at the cellular level. Ventricular myocytes were isolated from adult rat hearts and were stimulated to contract at 0.5 Hz. Contractile properties analysed included: peak shortening (PS), time‐to‐90%PS (TPS), time‐to‐90% relengthening (TR90), and fluorescence intensity change (ΔFFI). Nitric oxide synthase (NOS) activity was determined by the 3H‐arginine to 3H‐citrulline conversion assay.

Both Rb1 and Re exhibited dose‐dependent (1 – 1000 nM) inhibition in PS and ΔFFI, with maximal inhibitions between 20 – 25%. Concurrent application Rb1 and Re did not produce any additive inhibition on peak shortening amplitude (with a maximal inhibition of 24.9±6.1%), compared to Rb1 or Re alone. Pretreatment with the NOS inhibitor Nω‐nitro‐L‐arginine methyl ester (L‐NAME, 100 μM) abolished the effect of Rb1 and Re. Both Rb1 and Re significantly (P<0.05) stimulated NOS activity concentration‐dependently.

This study demonstrated a direct depressant action of ginsenosides on cardiomyocyte contraction, which may be mediated in part through increased NO production.

British Journal of Pharmacology (2001) 134, 1159–1165; doi:10.1038/sj.bjp.0704377
Differential regulation of endobiotic‐oxidizing cytochromes P450 in vitamin A‐deficient male rat liver
Authors: Murray Michael , Sefton Rachel M , Croft Kevin D , Butler Alison M
Published: January 2005

The hepatic CYP4A‐dependent ω‐hydroxylation of arachidonic acid and CYP2C11‐dependent 2α‐/16α‐hydroxylations of testosterone were decreased to 74 and 60% of respective control in microsomal fractions from vitamin A‐deficient rats. Decreases in the rates of arachidonic acid ω‐1‐hydroxylation and testosterone 6β‐, 7α‐ and 17α‐hydroxylations were less pronounced.

Corresponding decreases in microsomal CYP4A and CYP2C11 immunoreactive protein expression to 64 and 68% of respective control were observed in vitamin A‐deficient rat liver. Expression of CYP3A proteins was unchanged from vitamin A‐adequate control.

Northern analysis revealed a selective decrease in CYP4A2 mRNA expression in vitamin A‐deficient rat liver to ∼5% of control; expression of the related CYP4A1/4A3 mRNAs was not decreased. CYP2C11 mRNA expression was also decreased in vitamin A‐deficient male rat liver to 39% of control levels.

Intake of the deficient diet containing all‐trans‐retinoic acid (ATRA) during the final week of the experiment restored CYP4A2 mRNA and CYP4A protein. Administration of exogenous androgen or episodic growth hormone was ineffective. In contrast, CYP2C11 expression was restored by ATRA and androgen, but not by growth hormone.

From these studies it emerges that CYP4A2, a fatty acid ω‐hydroxylase in rat liver, is highly dependent on vitamin A for optimal expression, whereas CYP2C11 is indirectly down regulated by androgen deficiency resulting from vitamin A‐deficiency. Altered CYP expression in vitamin A‐deficiency provides insights into the relationship between dietary constituents and the intracellular formation of vasoactive eicosanoids as well as the clearance of androgenic steroids.

British Journal of Pharmacology (2001) 134, 1487–1497; doi:10.1038/sj.bjp.0704380
Protamine augments stretch induced calcium increase in vascular endothelium
Authors: Murase Kichiro , Naruse Keiji , Kimura Akira , Okumura Kenji , Hayakawa Tetsuo , Sokabe Masahiro
Published: January 2005

Human umbilical vein endothelial cells cultured on a transparent silicone chamber were subjected to a short stretch pulse (ca. 1 s, 5 – 25% stretch) of their substrate and following increases in intracellular Ca2+ concentration ([Ca2+]i) were measured by fluorescence intensity ratiometry using fura‐2.

In response to mechanical stretch, the cells in HEPES buffered saline exhibited a Ca2+ transient in a dose dependent way. The response was completely dependent on external Ca2+ and inhibited by gadolinium (Gd3+), suggesting that it was mediated by the activation of a stretch activated cation channel (SACatC).

Interestingly, the stretch induced Ca2+ transient was significantly augmented in the presence of basic polypeptide, protamine. This augmented Ca2+ response was inhibited neither by Gd3+ nor by the deprivation of external Ca2+, indicating that the SACatC is not responsible for this phenomenon.

In contrast, this augmentation was inhibited by depletion of intracellular Ca2+ stores with thapsigargin or by the pretreatment with phospholipase inhibitors such as U73122 and manoalide.

These results suggest the presence of a metabotropic mechanoreceptor distinct from the SACatC in vascular endothelium. This augmented [Ca2+]i increase may contribute to the vasodilating response induced by protamine during heparin neutralization in cardiac surgery.

British Journal of Pharmacology (2001) 134, 1403–1410; doi:10.1038/sj.bjp.0704386
Evidence of P‐glycoprotein mediated apical to basolateral transport of flunisolide in human broncho‐tracheal epithelial cells (Calu‐3)
Authors: Florea Bogdan I , Van Der Sandt Inez C J , Schrier S Mariette , Kooiman Klazina , Deryckere Koen , De Boer Albertus G , Junginger Hans E , Borchard Gerrit
Published: January 2005

Transepithelial transport of flunisolide was studied in reconstituted cell monolayers of Calu‐3, LLC‐PK1 and the MDR1‐P‐glycoprotein transfected LLC‐MDR1 cells.

Flunisolide transport was polarized in the apical (ap) to basolateral (bl) direction in Calu‐3 cells and was demonstrated to be ATP‐dependent. In LLC‐MDR1 cells, flunisolide was transported in the bl to ap direction and showed no polarization in LLC‐PK1 cells.

Non‐specific inhibition of cellular metabolism at low temperature (4°C) or by 2‐deoxy‐D‐glucose (2‐d‐glu) and sodium azide (NaN3) abolished the polarized transport. Polarized flunisolide transport was also inhibited by the specific Pgp inhibitors verapamil, SDZ PSC 833 and LY335979.

Under all experimental conditions and in the presence of all used inhibitors, no decrease in the TransEpithelial Electrical Resistance (TEER) values was detected. From all inhibitors used, only the general metabolism inhibitors 2‐deoxy‐D‐glucose and NaN3, decreased the survival of Calu‐3 cells.

Western blotting analysis and confocal laser scanning microscopy demonstrated the presence of MDR1‐Pgp at mainly the basolateral side of the plasma membrane in Calu‐3 cells and at the apical side in LLC‐MDR1 cells. Mass spectroscopy studies demonstrated that flunisolide is transported unmetabolized across Calu‐3 cells.

In conclusion, these results show that the active ap to bl transport of flunisolide across Calu‐3 cells is facilitated by MDR1‐Pgp located in the basolateral plasma membrane.

British Journal of Pharmacology (2001) 134, 1555–1563; doi:10.1038/sj.bjp.0704390
Evidence for two endothelin EtA receptor subtypes in rabbit arteriolar smooth muscle
Authors: Curtis Tim M , Scholfield C Norman
Published: January 2005

Effects of endothelin‐1 (Et‐1) were studied on membrane currents in choroidal arteriolar smooth muscle by using perforated patch‐clamp recordings.

Et‐1 (10 nM) activated oscillatory Ca2+‐activated Cl−‐currents (ICl(Ca)) which could not be reversed by washing out.

Currents through L‐type Ca2+ channels were resolved in a divalent free medium (ICa(L)Na). Et‐1 reduced ICa(L)Na by 75±7% within 30 s and this effect faded over 5 min, when the depression remained constant. On washing out Et‐1, ICa(L)Na almost completely recovered within 10 s.

BQ123 (1 μM), a peptide EtA receptor blocker, prevented the activation of ICl(Ca), but failed to inhibit ICl(Ca) transients once they had been initiated. In contrast, BQ123 not only prevented but also reversed the inhibition of ICa(L)Na by Et‐1. BQ788 (1 μM), an EtB receptor antagonist, did not prevent the activation of ICl(Ca) or the inhibition of ICa(L)Na by Et‐1.

ABT‐627 (10 nM), a non‐peptide EtA receptor antagonist also blocked the activation of ICl(Ca). However, on ICa(L)Na, ABT‐627 (10 nM) mimicked the action of Et‐1 an effect blocked by BQ123 suggesting that ABT‐627 acted as an agonist.

The data are consistent with choroidal arteriolar smooth muscle cells having two types of EtA receptor, one where BQ123 is an antagonist and ABT‐627 an agonist, where ligands dissociate freely and this receptor is coupled to inhibition of L‐type Ca2+ channels. In the other, BQ123 and ABT‐627 are both antagonists and with Et‐1 the receptor converts to a high affinity state producing the classical irreversible activation ICl(Ca).

British Journal of Pharmacology (2001) 134, 1787–1795; doi:10.1038/sj.bjp.0704393
Detailed characterization of cysteine‐less P‐glycoprotein reveals subtle pharmacological differences in function from wild‐type protein
Authors: Taylor Andrew M , Storm Janet , Soceneantu Loredana , Linton Kenneth J , Gabriel Mark , Martin Catherine , Woodhouse James , Blott Emma , Higgins Christopher F , Callaghan Richard
Published: January 2005

Subtle alterations in the coupling of drug binding to nucleotide hydrolysis were observed following mutation of all seven endogenous cysteine residues to serines in the human multidrug resistance transporter, P‐glycoprotein. Wild‐type (wt) and the mutant (cys‐less) forms of P‐gp were expressed in Trichoplusia ni (High Five) cells and purified by metal affinity chromatography in order to undertake functional studies.

No significant differences were observed in substrate ([3H]‐azidopine) binding to wt or cys‐less P‐gp. Furthermore, neither the transported substrate vinblastine, nor the modulator nicardipine, differed in their respective potencies to displace [3H]‐azidopine from the wt or cys‐less P‐gp. These results suggest that respective binding sites for these drugs were unaffected by the introduced cysteine to serine substitutions.

The Michaelis‐Menten characteristics of basal ATP hydrolysis of the two isoforms of P‐gp were identical. The maximal ATPase activity in the presence of vinblastine was marginally reduced whilst the Km was unchanged in cys‐less P‐gp compared to control. However, cys‐less P‐gp displayed lower overall maximal ATPase activity (62%), a decreased Km and a lower degree of stimulation (76%) in the presence of the modulator nicardipine.

Therefore, the serine to cysteine mutations in P‐gp may suggest that vinblastine and nicardipine transduce their effects on ATP hydrolysis through distinct conformational pathways. The wt and cys‐less P‐gp isoforms display similarity in their fundamental kinetic properties thereby validating the use of cys‐less P‐gp as a template for future cysteine‐directed structure/function analysis.

British Journal of Pharmacology (2001) 134, 1609–1618; doi:10.1038/sj.bjp.0704400
Modulation of cardiac activity by tachykinins in the rat substantia nigra
Authors: Lessard Andrée , Couture Réjean
Published: January 2005

The effects of tachykinin NK1, NK2 and NK3 receptor agonists and antagonists were measured on blood pressure (MAP) and heart rate (HR) after bilateral microinjection into the substantia nigra (SN) of awake, unrestrained rats.

Increasing doses (25 pmol – 1 nmol) of selective agonists at NK1 ([Sar9,Met(O2)11]SP), NK2 ([β‐Ala8]NKA(4 – 10)) and NK3 (senktide) receptors into the SN produced tachycardia which was selectively and reversibly blocked by the prior injection of tachykinin antagonists at NK1 (RP67580, 250 pmol), NK2 (SR48968, 250 pmol) and NK3 (R‐820, 500 pmol) receptor. A rapid fall in MAP followed by a pressor response was seen with 1 nmol of [Sar9,Met(O2)11]SP. Behavioural activity was elicited by 1 nmol of [Sar9,Met(O211]SP (sniffing>face washing=grooming) and senktide (sniffing>wet dog shake>rearing=locomotion). Tachykinin antagonists had no direct cardiovascular or behavioural effects.

The tachycardia produced by 100 pmol of [β‐Ala8]NKA(4 – 10) or senktide was abolished by an i.v. treatment with atenolol (β1‐adrenoceptor antagonist, 5 mg kg−1) while that evoked by [Sar9,Met(O2)11]SP was reduced. A combination of atenolol (5 mg kg−1) and atropine (muscarinic antagonist, 1 mg kg−1) blocked the response evoked by [Sar9,Met(O2)11]SP.

These data suggest that the SN is a potential site of modulation of cardiac activity by tachykinins. In addition to the withdrawal of the cardiovagal activity by NK1 receptor, the three tachykinin receptors appear to increase the sympatho/adrenal drive to the heart. This occurs independently of changes in MAP and behaviour. Hence, this study highlights a new central regulatory mechanism of cardiac autonomic activity.

British Journal of Pharmacology (2001) 134, 1749–1759; doi:10.1038/sj.bjp.0704401
Tumour necrosis factor‐alpha and leukotriene B4 mediate the neutrophil migration in immune inflammation
Authors: Canetti C , Silva J S , Ferreira S H , Cunha F Q
Published: January 2005

We investigated the mediators responsible for neutrophil migration induced by ovalbumin (OVA) in immunized mice and the mechanisms involved in their release.

OVA administration promoted dose‐ and time‐dependent neutrophil migration in immunized, but not in non‐immunized mice, which was mediated by leukotriene B4 (LTB4) and tumour necrosis factor (TNF)α, since it was inhibited by LTB4 synthesis inhibitor (MK 886) or by LTB4 receptor antagonist (CP 105,696), by dexamethasone and by antiserum to TNFα (82, 85, 63 and 87%, respectively). Confirming TNFα involvement, OVA challenge in immunized p55 TNF receptor deficient mice (p55−/−) did not promote neutrophil migration (control: 2.90±0.68; p55−/−: 0.92±0.23×106 neutrophils cavity−1).

OVA‐stimulated peritoneal cells from immunized mice released a neutrophil chemotactic factor which mimicked, in naive mice, neutrophil migration induced by OVA.

Supernatant chemotactic activity is due to TNFα and LTB4, since its release was inhibited by MK 886 (93%) and dexamethasone (90%), and significant amounts of these mediators were detected.

TNFα and LTB4 released by OVA challenge seem to act through a sequential mechanism, since MK 886 inhibited (88%) neutrophil migration induced by TNFα. Moreover, peritoneal cells stimulated with TNFα released LTB4.

CD4+ T cells are responsible for TNFα release, because the depletion of this subset prevented the release of TNFα (control: 400±25; immunized: 670±40; CD4+ depleted: 435±18 pg ml−1).

In conclusion, neutrophil migration induced by OVA depends on TNFα released by CD4+ cells, which acts through an LTB4‐dependent mechanism.

British Journal of Pharmacology (2001) 134, 1619–1628; doi:10.1038/sj.bjp.0704403
Nuclear factor kappa B is involved in lipopolysaccharide‐stimulated induction of interferon regulatory factor‐1 and GAS/GAF DNA‐binding in human umbilical vein endothelial cells
Authors: Liu Li , Paul Andrew , MacKenzie Christopher J , Bryant Clare , Graham Anne , Plevin Robin
Published: January 2005

In this study we examined the signalling events that regulate lipopolysaccharide (LPS)‐stimulated induction of interferon regulatory factor (IRF)‐1 in human umbilical vein endothelial cells (HUVECs).

LPS stimulated a time‐ and concentration‐dependent increase in IRF‐1 protein expression, an effect that was mimicked by the cytokine, tumour necrosis factor (TNF)‐α.

LPS stimulated a rapid increase in nuclear factor kappa B (NFκB) DNA‐binding activity. Pre‐incubation with the NFκB pathway inhibitors, N‐α‐tosyl‐L‐lysine chloromethyl ketone (TLCK) or pyrrolidine dithiocarbamate (PDTC), or infection with adenovirus encoding IκBα, blocked both IRF‐1 induction and NFκB DNA‐binding activity.

LPS and TNFα also stimulated a rapid activation of gamma interferon activation site/gamma interferon activation factor (GAS/GAF) DNA‐binding in HUVECs. Preincubation with the Janus kinase (JAK)‐2 inhibitor, AG490 blocked LPS‐stimulated IRF‐1 induction but did not affect GAS/GAF DNA‐binding.

Preincubation with TLCK, PDTC or infection with IκBα adenovirus abolished LPS‐stimulated GAS/GAF DNA‐binding.

Incubation of nuclear extracts with antibodies to RelA/p50 supershifted GAS/GAF DNA‐binding demonstrating the involvement of NFκB isoforms in the formation of the GAS/GAF complex.

These studies show that NFκB plays an important role in the regulation of IRF‐1 induction in HUVECs. This is in part due to the interaction of NFκB isoforms with the GAS/GAF complex either directly or via an intermediate protein.

British Journal of Pharmacology (2001) 134, 1629–1638; doi:10.1038/sj.bjp.0704404
Effects of moderate hypothermia on sarcolemmal Na+/H+ exchanger activity and its inhibition by cariporide in cardiac ventricular myocytes
Authors: Hoshino Kimihiko , Avkiran Metin
Published: January 2005

Specific inhibitors of the sarcolemmal Na+/H+ exchanger (NHE) such as cariporide are being evaluated for cardioprotective therapy during cardiac surgery. We determined the effects of moderate hypothermia (25°C), as occurs during cardiac surgery, on (1) sarcolemmal NHE activity and (2) the NHE‐inhibitory potency of cariporide, in isolated adult rat ventricular myocytes.

As the index of NHE activity, trans‐sarcolemmal acid efflux rate (JH) was determined by microepifluorescence in single cells (n=8 to 11 per group), during recovery from intracellular acidosis in bicarbonate‐free conditions.

Initially, myocytes were subjected to two consecutive acid pulses; these both occurred at 37°C in the normothermic control group but the second pulse was at 25°C in the moderate hypothermia group. JH values obtained after the first pulse were superimposed in both groups, indicating comparable cell populations. However, after the second pulse, JH values in the moderate hypothermia group were approximately 50% of those in the normothermic control group over the pHi range 6.80 – 7.10.

Similar results were obtained in cells subjected to a single acid pulse at 37 or 25°C, with JH values in the latter group measuring approximately 60% of those in the former over the pHi range 6.80 – 7.10.

Cariporide (0.01, 0.03, 0.1, 0.3, 1.0 or 3.0 μM), present during recovery from a single acid pulse, reduced JH in a concentration‐dependent manner, with IC50 values of 150 and 130 nM at 37 and 25°C, respectively.

We conclude that moderate hypothermia produces (1) a significant, but partial, inhibition of sarcolemmal NHE activity, and (2) no significant effect on the NHE‐inhibitory potency of cariporide.

British Journal of Pharmacology (2001) 134, 1587–1595; doi:10.1038/sj.bjp.0704405
DCPIB is a novel selective blocker of ICl,swell and prevents swelling‐induced shortening of guinea‐pig atrial action potential duration
Authors: Decher Niels , Lang Hans J , Nilius Bernd , Brüggemann Andrea , Busch Andreas E , Steinmeyer Klaus
Published: January 2005

We identified the ethacrynic‐acid derivative DCPIB as a potent inhibitor of ICl,swell, which blocks native ICl,swell of calf bovine pulmonary artery endothelial (CPAE) cells with an IC50 of 4.1 μM. Similarly, 10 μM DCPIB almost completely inhibited the swelling‐induced chloride conductance in Xenopus oocytes and in guinea‐pig atrial cardiomyocytes. Block of ICl,swell by DCPIB was fully reversible and voltage independent.

DCPIB (10 μM) showed selectivity for ICl,swell and had no significant inhibitory effects on ICl,Ca in CPAE cells, on chloride currents elicited by several members of the CLC‐chloride channel family or on the human cystic fibrosis transmembrane conductance regulator (hCFTR) after heterologous expression in Xenopus oocytes. DCPIB (10 μM) also showed no significant inhibition of several native anion and cation currents of guinea pig heart like ICl,PKA, IKr, IKs, IK1, INa and ICa.

In all atrial cardiomyocytes (n=7), osmotic swelling produced an increase in chloride current and a strong shortening of the action potential duration (APD). Both swelling‐induced chloride conductance and AP shortening were inhibited by treatment of swollen cells with DCPIB (10 μM). In agreement with the selectivity for ICl,swell, DCPIB did not affect atrial APD under isoosmotic conditions.

Preincubation of atrial cardiomyocytes with DCPIB (10 μM) completely prevented both the swelling‐induced chloride currents and the AP shortening but not the hypotonic cell swelling.

We conclude that swelling‐induced AP shortening in isolated atrial cells is mainly caused by activation of ICl,swell. DCPIB therefore is a valuable pharmacological tool to study the role of ICl,swell in cardiac excitability under pathophysiological conditions leading to cell swelling.

British Journal of Pharmacology (2001) 134, 1467–1479; doi:10.1038/sj.bjp.0704413
Urocortin relaxes rat tail arteries by a PKA‐mediated reduction of the sensitivity of the contractile apparatus for calcium
Authors: Lubomirov Lubomir , Gagov Hristo , Petkova‐Kirova Polina , Duridanova Dessislava , Kalentchuk Vjatscheslav U , Schubert Rudolf
Published: January 2005

Urocortin is an endogenous vasodilator although the mechanism of vasorelaxation is not completely understood. The hypothesis that an alteration of smooth muscle calcium concentration is involved was tested using isometric tension recording and calcium fluorimetry. The relationship between contraction and intracellular calcium was also estimated.

Urocortin produced a concentration dependent relaxation (pD2 8.59±0.06, n=6) of vessels pre‐contracted with a physiological salt solution containing 42 mM KCl (42 mM K‐PSS).

Removal of the endothelium did not alter the effect of urocortin, pD2 was 8.49±0.11, n=5.

Corticotropin‐releasing factor relaxed 42 mM K‐PSS pre‐contracted vessels with less potency compared to urocortin (pD2 6.99±0.28, n=5).

Urocortin at 100 nM relaxed vessels pre‐contracted with 42 mM K‐PSS by 59.6±4.6% (n=8) and vessels pre‐contracted with 500 nM noradrenaline by 25.2±6.8% (n=6). Both effects were not accompanied by a change in the intracellular calcium concentration.

Urocortin at 100 nM produced a significant rightward shift of 0.33±0.07 units of normalized intracellular calcium (n=5) of the relationship between tension and intracellular calcium.

The urocortin‐induced relaxation was considerably reduced in the presence of 0.3 mM Rp‐8‐CPT‐cAMPS, a cyclic AMP‐dependent protein kinase (PKA) inhibitor.

The PKA‐activator Sp‐5,6‐DCl‐cBIMPS relaxed 42 mM K‐PSS pre‐contracted vessels (pD2 4.98±0.07, n=6). Sp‐5,6‐DCl‐cBIMPS at 0.1 mM relaxed vessels by 85.3±2.5% (n=5), but did not change the intracellular calcium concentration.

In conclusion, the data show that urocortin is a potent, endothelium‐independent dilator of rat tail arteries and suggest that this effect is mediated by PKA causing a reduction of the sensitivity of the contractile apparatus for calcium.

British Journal of Pharmacology (2001) 134, 1564–1570; doi:10.1038/sj.bjp.0704418
Cibenzoline, an ATP‐sensitive K+ channel blocker, binds to the K+‐binding site from the cytoplasmic side of gastric H+,K+‐ATPase
Authors: Tabuchi Yoshiaki , Yashiro Hiroaki , Hoshina Satomi , Asano Shinji , Takeguchi Noriaki
Published: January 2005

Cibenzoline, (±)‐2‐(2,2‐diphenylcyclopropyl‐2‐imidazoline succinate, has been clinically used as one of the Class I type antiarrhythmic agents and also reported to block ATP‐sensitive K+ channels in excised membranes from heart and pancreatic β cells. In the present study, we investigated if this drug inhibited gastric H+,K+‐ATPase activity in vitro.

Cibenzoline inhibited H+,K+‐ATPase activity of permeabilized leaky hog gastric vesicles in a concentration‐dependent manner (IC50: 201 μM), whereas no effect was shown on Na+,K+‐ATPase activity of dog kidney (IC50: >1000 μM). Similarly, cibenzoline inhibited H+,K+‐ATPase activity of HEK‐293 cells (human embryonic kidney cell line) co‐transfected with rabbit gastric H+,K+‐ATPase α‐ and β‐subunit cDNAs (IC50: 183 μM).

In leaky gastric vesicles, inhibition of H+,K+‐ATPase activity by cibenzoline was attenuated by the addition of K+ (0.5 – 5 mM) in a concentration‐dependent manner. The Lineweaver‐Burk plot of the H+,K+‐ATPase activity shows that cibenzoline increases Km value for K+ without affecting Vmax, indicating that this drug inhibits H+,K+‐ATPase activity competitively with respect to K+.

The inhibitory effect of H+,K+‐ATPase activity by cibenzoline with normal tight gastric vesicles did not significantly differ from that with permeabilized leaky gastric vesicles, indicating that this drug reacted to the ATPase from the cytoplasmic side of the membrane.

These findings suggest that cibenzoline is an inhibitor of gastric H+,K+‐ATPase with a novel inhibition mechanism, which inhibits gastric H+,K+‐ATPase by binding its K+‐recognition site from the cytoplasmic side.

British Journal of Pharmacology (2001) 134, 1655–1662; doi:10.1038/sj.bjp.0704422
Prostanoid EP1‐ and TP‐receptors involved in the contraction of human pulmonary veins
Authors: Walch Laurence , De Montpreville Vincent , Brink Charles , Norel Xavier
Published: January 2005

To characterize the prostanoid receptors (TP, FP, EP1 and/or EP3) involved in the vasoconstriction of human pulmonary veins, isolated venous preparations were challenged with different prostanoid‐receptor agonists in the absence or presence of selective antagonists.

The stable thromboxane A2 mimetic, U46619, was a potent constrictor agonist on human pulmonary veins (pEC50=8.60±0.11 and Emax=4.61±0.46 g; n=15). The affinity values for two selective TP‐antagonists (BAY u3405 and GR32191B) versus U46619 were BAY u3405: pA2=8.94±0.23 (n=3) and GR32191B: apparent pKB=8.25±0.34 (n=3), respectively. These results are consistent with the involvement of TP‐receptor in the U46619 induced contractions.

The two EP1‐/EP3‐ agonists (17‐phenyl‐PGE2 and sulprostone) induced contraction of human pumonary veins (pEC50=8.56±0.18; Emax=0.56±0.24 g; n=5 and pEC50=7.65±0.13; Emax=1.10±0.12 g; n=14, respectively). The potency ranking for these agonists: 17‐phenyl‐PGE2>sulprostone suggests the involvement of an EP1‐receptor rather than EP3. In addition, the contractions induced by sulprostone, 17‐phenyl‐PGE2 and the IP‐/EP1‐ agonist (iloprost) were blocked by the DP‐/EP1‐/EP2‐receptor antagonist (AH6809) as well as by the EP1 antagonist (SC19220).

PGF2α induced small contractions which were blocked by AH6809 while fluprostenol was ineffective. These results indicate that FP‐receptors are not implicated in the contraction of human pulmonary veins.

These data suggest that the contractions induced by prostanoids involved TP‐ and EP1‐receptors in human pulmonary venous smooth muscle.

British Journal of Pharmacology (2001) 134, 1671–1678; doi:10.1038/sj.bjp.0704423
Effect of ABT‐627 (A‐147627), a potent selective ETA receptor antagonist, on the cardiopulmonary profile of newborn lambs with surgically‐induced diaphragmatic hernia
Authors: Kavanagh Mélanie , Battistini Bruno , Jean Sonia , Crochetière Josiane , Fournier Louis , Wessale Jerry , Opgenorth Terry J , Cloutier Raymond , Major Diane
Published: January 2005

Postnatal mortality in isolated congenital diaphragmatic hernia (CDH) is mainly related to the associated pulmonary hypertension (PH) and to right‐to‐left shunting.

Endothelins (ETs) are potent vasoconstrictors and pro‐mitogenic peptides. Strong evidences support their participation in CDH and in the etiology of PH via the activation of ETA receptors (ETA‐Rs).

Evaluation of the effect of ABT‐627, a selective non‐peptidic ETA‐R antagonist, given from −15 to 210 min post‐delivery (1 mg kg−1 bolus +0.01 mg kg−1 h−1 infusion, i.v.), was conducted in the lamb model of CDH.

Severity of CDH was assessed in comparison to untreated controls (n=5). Untreated CDH lambs (n=7) had a higher mean pulmonary arterial pressure (MPAP; P<0.0001), lower mean blood pressure (MBP; P=0.0004), higher MPAP / MBP ratio (P<0.0001), lower arterial pH (P<0.0001), higher paCO2 (P<0.0001), lower paO2 (P<0.0001) and lower post‐ductal pulsatile SaO2 (P<0.0001) than untreated controls.

Treated controls (n=7) showed a higher MPAP, lower MBP, higher MPAP/MBP ratio, lower arterial pH, higher paCO2, lower paO2, lower post‐ductal pulsatile SaO2 and lower plasmatic ir‐ET ratios compared to untreated controls (P<0.0001).

Treated CDH lambs (n=8) showed a higher MBP (P<0.0001), lower MPAP / MBP ratio (P<0.0001), higher arterial pH (P<0.0001), lower paCO2 (P<0.0001), higher paO2 (P=0.0228), higher post‐ductal pulsatile SaO2 (P=0.0016) and lower plasmatic ir‐ET ratios (P=0.0247) when compared to untreated CDH lambs.

These observations revealed that, although acute perinatal treatment with a selective non‐peptidic ETA‐R antagonist had some adverse effects in controls, it attenuated the progressive cardiopulmonary deterioration that occurred after birth in CDH lambs.

British Journal of Pharmacology (2001) 134, 1679–1688; doi:10.1038/sj.bjp.0704424
Haeme oxygenase‐1 and cardiac anaphylaxis
Authors: Ndisang Joseph Fomusi , Wang Rui , Vannacci Alfredo , Marzocca Cosimo , Fantappiè Ornella , Mazzanti Roberto , Mannaioni Pier Francesco , Masini Emanuela
Published: January 2005

Haeme oxygenase (HO) is an enzyme mainly localized in the smooth endoplasmic reticulum and involved in haeme degradation and in the generation of carbon monoxide (CO). Here we investigate (1) whether the inducible isoform of HO (HO‐1) is expressed in the isolated heart of the guinea‐pig and (2) the functional significance of HO‐1 on the response to antigen in isolated hearts taken from actively sensitized guinea‐pigs.

Both the HO‐1 expression and activity are consistently increased in hearts from guinea‐pigs pretreated with hemin, an HO‐1 inducer (4 mg kg−1 i.p., 18 h before antigen challenge). The administration of the HO‐1 inhibitor zinc‐protoporphyrin IX (ZnPP‐IX, 50 μmol kg−1, i.p., 6 h before hemin) abolished the increase of both the HO‐1 expression and activity.

In vitro challenge with the specific antigen of hearts from actively sensitized animals evokes a positive inotropic and chronotropic effect, a coronary constriction followed by dilation and an increase in the amount of histamine in the perfusates. In hearts from hemin‐pretreated animals, antigen challenge did not modify the heart rate and the force of contraction; the coronary outflow was significantly increased and a diminution of the release of histamine was observed. The patterns of cardiac anaphylaxis were fully restored in hearts from animals treated with ZnPP‐IX 6 h before hemin.

In isolated hearts perfused with a Tyrode solution gassed with 100% CO for 5 min and successively reoxygenated, the response to antigen was similar to that observed in hearts from hemin‐pretreated animals.

Pretreatment with hemin or the exposure to exogenous CO were linked to an increase in cardiac cyclic GMP levels and to a decrease of tissue Ca2+ levels.

The study demonstrates that overexpression of HO‐1 inhibits cardiac anaphylaxis through the generation of CO which, in turn, decreases the release of histamine through a cyclic GMP‐ and Ca2+‐dependent mechanism.

British Journal of Pharmacology (2001) 134, 1689–1696; doi:10.1038/sj.bjp.0704427
[Gly14]‐Humanin improved the learning and memory impairment induced by scopolamine in vivo
Authors: Mamiya Takayoshi , Ukai Makoto
Published: January 2005

Humanin is a very recently discovered 24 amino acid linear polypeptide, which protects against cell death induced by either familial Alzheimer's disease mutant of amyloid precursor protein, presenilin‐1 or presenilin‐2 in vitro. However, it has remained uncertain whether humanin is a useful drug for the animal model of learning and memory deficit. In this study, we evaluated the effects of [Gly14]‐humanin, a more potent humanin analogue, on the scopolamine HBr (1 mg kg−1 s.c.)‐induced impairment of spontaneous alternation behaviour in the Y‐maze, an index of short‐term memory in mice. [Gly14]‐Humanin (1000 pmol 5 μl−1 i.c.v.) reversed the impairment without affecting the number of arm entries. These results suggest that (I) [Gly14]‐humanin is a beneficial drug for the impairment of learning and memory and (II) it modulates the learning and memory function mediated via cholinergic systems in mice.

British Journal of Pharmacology (2001) 134, 1597–1599; doi:10.1038/sj.bjp.0704429
Evidence for the presence of A1 adenosine receptors in the aorta of spontaneously hypertensive rats
Authors: Fahim Mohammed , Mustafa Syed Jamal
Published: January 2005

Isolated aortic rings (endothelium‐intact and ‐denuded) from spontaneously hypertensive (SHR) and Wistar‐Kyoto (WKY) rats were used in this study to examine the vasoactive effects of various adenosine analogues.

In phenylephrine contracted aortic rings, concentration‐response curves were constructed by cumulative additions (10−11 – 10−5 M) of (2S)‐N6‐[2‐endo‐Norbornyl] adenosine (ENBA), N6‐cyclopentyladenosine (CPA), R‐N6‐(2‐phenylisopropyl) adenosine (R‐PIA), 2‐p‐(‐2‐carboxyethyl) phenethylamino‐5′‐N‐thylcarboxamido adenosine (CGS‐21680).

A non‐specific adenosine receptor agonist 2‐chloroadenosine (CAD) resulted in biphasic response with a small contraction at lower concentrations (10−9 – 10−8 M) followed by a significant relaxation at higher concentration in endothelium‐intact SHR tissues, suggesting presence of both A1 and A2 adenosine receptors in SHR aorta. However, only relaxation was observed in WKY.

Contractile response in SHR had the following rank order of potency: ENBA>CPA>R‐PIA>CAD. The relaxation response in SHR and WKY had the following rank order of potency: CGS 21680>CAD>R‐PIA>CPA>ENBA.

Removal of endothelium abolished the adenosine analogue induced contractions in SHR aorta and attenuated the vasorelaxation responses in the WKY and SHR.

The contractile response in SHR was abolished by A1 adenosine receptor antagonist N6‐endonorbornan‐2‐yl‐9‐methyladenine (N‐0861). A2 adenosine receptor antagonist, 3,7‐dimethyl‐1‐proparglyxanthine (DMPX) did not affect the contraction response of adenosine analogues.

Endothelium‐dependent contractions elicited by A1 receptor agonists were blocked by indomethacin and by free radical scavengers.

These data suggest that the contractile response to adenosine analogues in SHR aorta is probably mediated by free radicals which are generated through the increased cyclo‐oxygenase activity occurring in the vascular endothelium of SHR but not the WKY rats.

British Journal of Pharmacology (2001) 134, 1760–1766; doi:10.1038/sj.bjp.0704433