bluuebunny/crossref_metadata_2025_split huggingface dataset:
Hydrogen peroxide‐induced impairment of reactivity in rat isolated aorta: potentiation by 3‐amino‐1,2,4‐triazole
Authors: Mian Kousar B. , Martin William 
Published: August 2006

In this study the impairment induced by hydrogen peroxide of vascular reactivity and the role of endogenous catalase in protection against this impairment was assessed in isolated rings of rat aorta.
Incubation with hydrogen peroxide at 1 mM, but not at 0.1 mM, for 15, 30 or 60 min followed by washout depressed, in a time‐dependent manner, the subsequent ability of endothelium‐containing and endothelium‐denuded rings to contract to phenylephrine.
Incubation with 3‐amino‐1,2,4‐triazole (50 mM, 90 min, followed by washout) to inhibit endogenous catalase had no effect by itself on subsequent phenylephrine‐induced contraction. However, pretreatment with 3‐amino‐1,2,4‐triazole did lead to a profound enhancement of the ability of hydrogen peroxide (1 mM, present for the final 30 min of the 90 min incubation, followed by washout) to depress phenylephrine‐induced contraction in both endothelium‐containing and endothelium‐denuded rings.
Incubation with hydrogen peroxide at 1 mM, but not at 0.1 mM, for 15, 30 or 60 min followed by washout inhibited, in a time‐dependent manner, the subsequent ability of acetylcholine (10 nM–3 μM) to induce endothelium‐dependent relaxation. Furthermore, incubation with hydrogen peroxide 1 mM (30 min, followed by washout) also inhibited relaxation induced by glyceryl trinitrate (1–100 nM) or isoprenaline (10 nM–3 μM) in endothelium‐denuded rings.
Incubation with 3‐amino‐1,2,4‐triazole (50 mM, 90 min, followed by washout) had no effect by itself on relaxation induced by acetylcholine, glyceryl trinitrate or isoprenaline. In contrast, pretreatment with 3‐amino‐1,2,4‐triazole led to profound enhancement of the ability of hydrogen peroxide (1 mM, present for final 30 min of the 90 min incubation) to block relaxation to acetylcholine, glyceryl trinitrate or isoprenaline.
On the basis of the actions of 3‐amino‐1,2,4‐triazole, it is likely that endogenous catalase plays an important role in the protection of vascular reactivity of rat aorta against oxidant damage by high (1 mM) but not lower (0.1 mM) concentrations of hydrogen peroxide. The data are consistent with the promotion of non‐selective damage to the vascular smooth muscle cells by hydrogen peroxide, but endothelial damage may also be sustained.

British Journal of Pharmacology (1997) 121, 813–819; doi:10.1038/sj.bjp.0701187
The involvement of ATP‐sensitive potassium channels in β2‐adrenoceptor agonist‐induced vasodilatation on rat diaphragmatic microcirculation
Authors: Chang Han‐Yu 
Published: August 2006

The effects of glibenclamide (GLB), a blocker of ATP‐sensitive potassium (KATP) channels, on diaphragmatic microcirculation in male Sprague‐Dawley rats were assessed under basal conditions and after β2‐adrenoceptor‐agonist stimulation. In addition, forskolin was used to bypass β‐adrenoceptors and GTP‐binding proteins (G‐protein) to explore the possible mechanism of GLB effects. For comparison, the relationships between KATP channel activity and cyclic GMP‐mediated vasodilator responses to acetylcholine (ACh) and sodium nitroprusside (SNP) were also assessed.
Male Sprague‐Dawley rats were anaesthetized with urethane and mechanically ventilated. The left hemi‐diaphragm of each rat was prepared and microvascular blood flow (QLDF) was recorded with laser‐Doppler flowmetry during continuous superfusion with bicarbonate‐buffered, prewarmed Ringer solution. The drugs were topically applied to the surface of the hemi‐diaphragm.
Salbutamol (0.32–32 μM), terbutaline (0.32 μM–0.32 μM) and forskolin (0.32–10 μM) each elicited a concentration‐dependent increase in QLDF.
Baseline microvascular blood flow was unaffected by a 30 min suffusion of 1 μM GLB (295±51 mV vs 325±62 mV, P=0.738).
The vasodilator response elicited by salbutamol (0.32 μM, 1 μM and 3.2 μM), was significantly attenuated by a 30 min superfusion with 1 μM GLB; this salbutamol‐induced vasodilatation was mediated via an interaction with β‐adrenoceptor receptors, as in other experiments it was greatly inhibited by 30‐min superfusion with propranolol (10 μM).
Similarly, following 30‐min superfusion with GLB (1 μM), the terbutaline (1 μM, 3.2 μM and 10 μM)‐induced vasodilator response was almost abolished and the vasodilator responses induced by incremental concentrations of forskolin (0.32 μM, 1 μM and 3.2 μM) were also significantly attenuated.
Cromakalim (1.5 μM, 3 μM and 3.2 μM) produced an increase of QLDF in a dose‐dependent manner, which was virtually abolished by GLB (1 μM). In contrast, the vasodilator responses induced by acetylcholine (32 μM, 0.1 mM, and 0.32 mM) or sodium nitroprusside (3.2 μM, 10 μM and 20 μM) were independent of GLB (1 μM).
In conclusion, KATP channels may be functional, but tonically inactive in the resting diaphragmatic microcirculation and the vasodilator effect of β2‐adrenoceptor agonists may be partly mediated by KATP channels; the activation of KATP channels may involve the accumulation of cyclic AMP in vascular smooth muscle cells.
Inhibition of 5‐hydroxytryptamine‐induced phosphoinositide hydrolysis and Ca2+ mobilization in canine cultured tracheal smooth muscle cells by phorbol ester
Authors: Yang Chuen‐Mao , Fen Lir‐Wan , Tsao Hui‐Liang , Chiu Chi‐Tso 
Published: August 2006

Regulation of the increase in inositol‐1,4,5‐trisphosphate (IP3) production and intracellular Ca2+ concentration ([Ca2+]i by protein kinase C (PKC) was investigated in canine cultured tracheal smooth muscle cells (TSMCs). Stimulation of TSMCs by 5‐hydroxytryptamine (5‐HT) caused an initial transient [Ca2+]i peak followed by a sustained elevation of [Ca2+]i in a concentration‐dependent manner.
Pretreatment of TSMCs with phorbol 12‐myristate 13‐acetate (PMA, 1 μM) for 30 min blocked the 5‐HT‐induced IP3 formation and Ca2+ mobilization. This inhibition was reduced after the cells had been incubated with PMA for 8 h, and within 48 h the 5‐HT‐induced Ca2+ mobilization reached the same extent as control cells.
The concentration of PMA that gave half‐maximal inhibition of 5‐HT‐induced increase in [Ca2+]i was 4 nM. Pretreatment of TSMCs with staurosporine (1 μM) of GF109203X (0.1 μM), PKC inhibitors, inhibited the ability of PMA to attenuate 5‐HT‐induced responses, suggesting that the inhibitory effect of PMA was mediated through the activation of PKC.
In parallel with the effect of PMA on 5‐HT‐induced IP3 formation and Ca2+ mobilization, the translocation and down‐regulation of PKC isozymes were determined by Western blot analysis in TSMCs. Analysis of cell extracts by Western blotting with antibodies against different PKC isozymes revealed that TSMCs expressed PKC‐α, βI, βII, δ, ε, θ and ζ. With PMA treatment of the cells for various times, translocation of PKC‐α, βI, βII, δ, ε and θ from the cytosol to the membrane was seen after 5 min, 30 min, 2 h, and 4 h treatment. However, 24 h treatment caused a partial down‐regulation of these PKC isozymes PKC‐ζ was not significantly translocated and down‐regulated at any of the times tested.
In conclusion, these results suggest that activation of PKC may inhibit the receptor‐mediated phosphoinositide hydrolysis and consequently attenuate the [Ca2+]i increase or inhibit both responses independently. The translocation of PKC‐α, βI, βII, δ, ε, and θ induced by PMA caused an attenuation of 5‐HT‐stimulated IP3 accumulation and Ca2+ mobilization in TSMCs.
Effects of [3H]‐BIDN, a novel bicyclic dinitrile radioligand for GABA‐gated chloride channels of insects and vertebrates
Authors: Rauh James J , Benner Eric , Schnee Michael E , Cordova Daniel , Holyoke Caleb W , Howard Michael H , Bai Donglin , Buckingham Steven D , Hutton Michael L , Hamon Alain , Roush Richard T , Sattelle David B 
Published: August 2006

The radiolabelled bicyclic dinitrile, [3H]‐3,3‐bis‐trifluoromethyl‐bicyclo[2.2.1]heptane‐2,2‐dicarbonitrile ([3H]‐BIDN), exhibited, specific binding of high affinity to membranes of the southern corn rootworm (Diabrotica undecimpunctata howardi) and other insects. A variety of γ‐aminobutyric acid (GABA) receptor convulsants, including the insecticides heptachlor (IC50, 35±3 nM) and dieldrin (IC50, 93±7 nM), displaced [3H]‐BIDN from rootworm membranes. When tested at 100 μM, 1‐(4‐ethynylphenyl)‐4‐n‐propyl‐2,6,7‐trioxabicyclo[2.2.2]octane(EBOB), 4‐t‐butyl‐2,6,7‐trioxa‐1‐phosphabicyclo[2.2.2]octane‐1‐thione (TBPS), 1‐phenyl‐4‐t‐butyl‐2,6,7‐trioxabicyclo[2.2.2]octane (TBOB) and picrotoxin failed to displace 50% of [3H]‐BIDN binding to rootworm membranes indicating that the bicyclic dinitrile radioligand probes a site distinct from those identified by other convulsant radioligands.
Dissociation studies showed that dieldrin, ketoendrin, toxaphene, heptachlor epoxide and α and β endosulphan displace bound [3H]‐BIDN from rootworm membranes by a competitive mechanism.
Rat brain membranes were also shown to possess a population of saturable, specific [3H]‐BIDN binding sites, though of lower affinity than in rootworm and with a different pharmacological profile. Of the insecticidal GABAergic convulsants that displaced [3H]‐BIDN from rootworm, cockroach (Periplaneta americana) and rat brain membranes, many were more effective in rootworm.
Functional GABA‐gated chloride channels of rootworm nervous system and of cockroach nerve and muscle were blocked by BIDN, whereas cockroach neuronal GABAB receptors were unaffected.
Expression in Xenopus oocytes of either rat brain mRNA, or cDNA‐derived RNA encoding a GABA receptor subunit (Rdl) that is expressed widely in the nervous system of Drosophila melanogaster resulted in functional, homo‐oligomeric GABA receptors that were blocked by BIDN. Thus, BIDN probes a novel site on GABA‐gated Cl− channels to which a number of insecticidally‐active molecules bind.
Neocuproine, a selective Cu(I) chelator, and the relaxation of rat vascular smooth muscle by S‐nitrosothiols
Authors: Al‐Sa'doni H H , Megson I L , Bisland S , Butler A R , Flitney F W 
Published: August 2006

A study has been made of the effect of neocuproine, a specific Cu(I) chelator, on vasodilator responses of rat isolated perfused tail artery to two nitrosothiols: S‐nitroso‐N‐acetyl‐d,l‐penicillamine (SNAP) and S‐nitroso‐glutathione (GSNO).
Bolus injections (10μl) of SNAP or GSNO (10−7–10−3m) were delivered into the lumen of perfused vessels pre‐contracted with sufficient phenylephrine (1–7μm) to develop pressures of 100–120mmHg. Two kinds of experiment were made: SNAP and GSNO were either (a) pre‐mixed with neocuproine (10−4m) and then injected into arteries; or (b) vessels were continuously perfused with neocuproine (10−5m) and then injected with either pure SNAP or GSNO.
In each case, neocuproine significantly attenuated vasodilator responses to both nitrosothiols, although the nature of the inhibitory effect differed in the two types of experiment. We conclude that the ability of exogenous nitrosothiols to relax vascular smooth muscle in our ex vivo model is dependent upon a Cu(I) catalyzed process. Evidence is presented which suggests that a similar Cu(I)‐dependent mechanism is responsible for the release of NO from endogenous nitrosothiols and that this process may assist in maintaining vasodilator tone in vivo.
Differential contribution of two serine residues of wild type and constitutively active β2‐adrenoceptors to the interaction with β2‐selective agonists
Authors: Kikkawa Hideo , Kurose Hitoshi , Isogaya Masafumi , Sato Yoji , Nagao Taku 
Published: August 2006

We have studied the difference in receptor binding activity between partial and full β2‐adrenoceptor agonists and the abilities of the agonists to interact with Ser204 and Ser207 in the fifth transmembrane region of the β2‐adrenoceptor, amino acid residues that are important for activation of the β2‐adrenoceptor.
In the binding study with [125I]‐iodocyanopindolol, the Ki values of (±)‐salbutamol, (±)‐salmeterol, TA‐2005 and (−)‐isoprenaline for the β2‐adrenoceptor expressed in COS‐7 cell membranes were 3340, 21.0, 12.0 and 904nm, respectively. The β1/β2 selectivity of these agonists was in the order of (±)‐salmeterol (332 fold)>TA‐2005 (52.8)>(±)‐salbutamol (6.8)>(−)‐isoprenaline (1.1), and the β3‐/β2‐adrenoceptor selectivity of these agonists was in the order of TA‐2005 (150 fold)>(±)‐salmeterol (88.6)>(±)‐salbutamol (10.4)>(−)‐isoprenaline (3.2).
The maximal activation of adenylyl cyclase by stimulation of the β1‐, β2‐ and β3‐adrenoceptors by TA‐2005 was 32, 100 and 100% of that by (−)‐isoprenaline, respectively, indicating that TA‐2005 is a full agonist at the β2‐ and β3‐adrenoceptors and a partial agonist at the β1‐adrenoceptor. (±)‐Salbutamol and (±)‐salmeterol were partial agonists at both β1‐ (8% and 9% of (−)‐isoprenaline) and β2‐ (83% and 74% of (−)‐isoprenaline) adrenoceptors.
The affinities of full agonists, TA‐2005 and (−)‐isoprenaline, were markedly decreased by substitution of Ala for Ser204 (S204A) of the β2‐adrenoceptor, whereas this substitution slightly reduced the affinities of partial agonists, (±)‐salbutamol and (±)‐salmeterol. Although the affinities of full agonists for the S207A‐β2‐adrenoceptor were decreased, those of partial agonists for the S207A‐β2‐adrenoceptor were essentially the same as for the wild type receptor.
The constitutively active mutant (L266S, L272A) of the β2‐adrenoceptor had an increased affinity for all four agonists. The affinities of full agonists were decreased by substitution of Ser204 of the constitutively active mutant, whereas the degree of decrease was smaller than that caused by the substitution of the wild type receptor. Although the affinities of (±)‐salbutamol and (±)‐salmeterol for the S207A‐β2‐adrenoceptor were essentially the same as those for the wild type β2‐adrenoceptor, the affinities of (±)‐salbutamol and (±)‐salmeterol for the constitutively active β2‐adrenoceptor were decreased by substitution of Ser207.
These results suggest that Ser204 and Ser207 of the wild type and constitutively active β2‐adrenoceptors differentially interacted with β2‐selective agonists.
Noradrenaline release and the effect of endogenous activation of the phospholipase C/protein kinase C signalling pathway in rat atria
Authors: Majewski H , Kotsonis P , Murphy T V , Barrington M 
Published: August 2006

It has been proposed that protein kinase C (PKC) in sympathetic nerves is activated during action‐potential evoked release of noradrenaline and helps maintain transmitter output. We studied this phenomenon further in rat atria radiolabelled with [3H]‐noradrenaline.
Noradrenaline release was elevated by continuous electrical stimulation of the atria for 10min at either 5 or 10Hz. Two inhibitors of PKC, polymyxin B (21μm) and Ro 318220 (3μm), markedly inhibited the release of noradrenaline but only at the higher stimulation frequency.
Further experiments were conducted with 10Hz stimulation but for shorter train durations. In this case polymyxin B inhibited noradrenaline release during a 10 or 15s train of impulses but not during a 5s train. This suggests that PKC effects are induced during the stimulation train by some process.
The diacylglycerol kinase inhibitor R59949 (10μm), which prevents the breakdown of diacylglycerol, enhanced noradrenaline release elicited by stimulation at 10Hz for 10 or 15s. This effect was not seen if polymyxin B was present and suggests that diacylglycerol is the endogenous activator of PKC.
The source of the diacylglycerol may be through phospholipase C pathways, since the phospholipase C inhibitor U73122 (3μm) inhibited noradrenaline release at 10Hz for 10s and the effect was not seen if polymyxin B was also present.
It is unlikely that phospholipase D is the source of diacylglycerol. Although the phospholipase D inhibitor wortmannin (1μm) inhibited noradrenaline release, this effect was still observed in the presence of polymyxin B. Furthermore ethanol, which inhibits diacylglycerol formation by phospholipase D, had no effect on noradrenaline release.
We therefore suggest that during a train of high frequency pulses phospholipase C is activated and this results in the production of diacylglycerol which in turn activates PKC. This enables the neurones to maintain transmitter release at a high level.
Characterization of angiotensin II formation in human isolated bladder by selective inhibitors of ACE and human chymase: a functional and biochemical study
Authors: Waldec Kristian , Fredrik Lindberg B , Persson Katarina , Andersson Karl‐Erik 
Published: August 2006

Functional recordings of smooth muscle tension and biochemical experiments on membrane fractions were performed to characterize angiotensin II (AII) formation in human isolated bladder smooth muscle.
A novel human chymase inhibitor CH 5450 (Z‐Ile‐Glu‐Pro‐Phe‐CO2Me) and a recently developed human chymase substrate Pro11‐,d‐Ala12)‐angiotensin I, claimed to be resistant to angiotensin converting enzyme (ACE) and carboxypeptidase, were used.
Angiotensin I (AI) (0.3μm) induced a contractile response amounting to 58±5% (n=12) of the initial K+ (124mm)‐induced contractions. This response was reduced to 36±3% (n=8) by the ACE‐inhibitor enalaprilat (10μm), while pretreatment with soybean trypsin inhibitor (STI 200μg ml−1) or CH 5450 (10μm) had no effect. However, the combination of enalaprilat and STI reduced the AI‐induced contractions to 19±5% (n=6), and the combination of enalaprilat and CH 5450 caused an almost complete inhibition of the AI‐induced contractions to 1±1% (n=6).
The substrate (Pro11‐,d‐Ala12)‐AI (3μm) produced contractions which amounted to 57±4% (n=13) of the initial K+ (124mm) contractions. These contractions were not affected by enalaprilat (10μm). On the other hand, STI (200μgml−1) and CH 5450 (10μm) added separately, depressed the (Pro11‐,d‐Ala12)‐AI‐induced contractions to 34±5% (n=6) and 24±4% (n=6), respectively. The combination of enalaprilat and STI or enalaprilat and CH 5450 did not produce any further inhibition.
Experiments with detrusor membrane fractions incubated with AI (50μm) were performed. In the presence of enalaprilat (100μm), carboxypeptidase inhibitor CPI (10μgml−1) and aprotinin (15μm), CH 5450 (10nm–1μm) caused a concentration‐dependent inhibition of AII formation.
The results confirm that AII is a potent contractile agent in the human isolated detrusor muscle. They also indicate that the serine protease responsible for AII formation in the human bladder in vitro is human chymase or an enzyme similar to human chymase.
Signalling pathways in bradykinin‐ and nitric oxide‐induced hypotension in the normotensive rat; role of K+‐channels
Authors: Berg Torill , Koteng Øyvind 
Published: August 2006

Bradykinin and nitric oxide (NO) are potent hypotensive agents. In the present study, the role of K+‐channels in the signalling pathways responsible for their hypotensive action was investigated in normotensive, anaesthetized rats. The rats were treated with ion‐channel inhibitors before administration of bradykinin (2.8, 5.6, 28 and 56nmolkg−1, i.v.) followed in some of the protocols by nitroprusside (1.1, 3.5, 7, 14, and 28nmolkg−1, i.v.).
No attenuation of the hypotensive response to bradykinin was detected for inhibitors of the Na‐K‐Cl‐cotransporter (30μmolkg−1 furosemide), the ATP‐sensitive K+‐channel (40μmolkg−1 glibenclamide), high conductance Ca2+‐activated K+‐channel (180μmolkg−1 tetraethylammonium, 54μmolkg−1 tetrabutylammonium, 35nmolkg−1 iberiotoxin, 35nmolkg−1 charybdotoxin) or the low conductance Ca2+‐activated K+‐channel (74nmolkg−1 apamin).
However, the voltage‐sensitive K+‐channel (IA) inhibitor 4‐aminopyridine (4.05–40.5μmolkg−1) induced a concentration‐dependent (P<0.0001) attenuation of the hypotensive response (P<0.0001). Bradykinin had no effect on heart rate in anaesthetized rats and this observation was not altered by pretreatment with 4‐aminopyridine.
4‐Aminopyridine (53μmolkg−1) also significantly attenuated the hypotensive response to nitroprusside (P<0.0003) without altering the heart rate concentration‐response curve. Of the two Ca2+‐activated K+‐channel inhibitors tested on nitroprusside‐induced hypotension, tetrabutylammonium induced a slight attenuation (P<0.0101), whereas iberiotoxin had no effect.
We therefore concluded that, although the acute hypotensive response to bradykinin in the normotensive rat is not mediated through nitric oxide synthesis, the hypotensive response to both agents was mediated through opening of voltage‐sensitive K+‐channels (IA), resulting in a decrease in peripheral vascular resistance.
Predominant role of A1 adenosine receptors in mediating adenosine induced vasodilatation of rat diaphragmatic arterioles: involvement of nitric oxide and the ATP‐dependent K+ channels
Authors: Danialou Gawiyou , Vicaut Eric , Sambe Abdoulaye , Aubier Michel , Boczkowski Jorge 
Published: August 2006

We investigated, by intravital microscopy in rats, the role of the subtypes of adenosine receptors A1 (A1/AR) and A2 (A2AR) in mediating adenosine‐induced vasodilatation of second and third order arterioles of the diaphragm.
Adenosine, and the A1AR selective agonists R(−)‐N6‐(2‐phenylisopropyl)‐adenosine (R‐PIA) and N6‐cyclo‐pentyl‐adenosine (CPA) induced a similar concentration‐dependent dilatation of diaphragmatic arterioles. The non selective A2AR subtype agonist N6‐[2‐(3,5‐dimethoxyphenyl)‐2‐(2‐methylphenyl) ethyl]adenosine (DPMA) also dilated diaphragmatic arterioles but induced a significantly smaller dilatation than adenosine. By contrast the selective A2aAR subtype agonist 2‐[p‐(2‐carboxyethyl)phenyl amino]‐5′‐N‐ethyl carboxamido adenosine (CGS 21680) did not modify diaphragmatic arteriolar diameter.
The non selective adenosine receptor antagonist 1,3‐dipropyl‐8‐p‐sulphophenylxanthine (SPX, 100 μM) and the selective A1AR antagonist 8‐cyclopentyl‐1,3‐dipropylxanthine (CPX, 50 nM) significantly attenuated adenosine‐induced dilatation of diaphragmatic arterioles. By contrast, adenosine significantly dilated diaphragmatic arterioles in the presence of A2AR antagonist 3,7‐dimethyl‐1‐propargylxanthine (DMPX, 10 μM).
The dilatation induced by adenosine was unchanged by the mast cell stabilizing agent sodium cromoglycate (cromolyn, 10 μM).
The nitric oxide (NO) synthase inhibitor Nω‐nitro‐L‐arginine (L‐NOARG, 300 μM) attenuated the dilatation induced by adenosine, and by the A1AR and A2AR agonists.
The ATP‐dependent K+ channel blocker glibenclamide (3 μM) significantly attenuated diaphragmatic arteriolar dilatation induced by adenosine and by the A1AR agonists R‐PIA and CPA. By contrast, glibenclamide did not significantly modify arteriolar dilatation induced by the A2AR agonist DPMA.
These findings suggest that adenosine‐induced dilatation of diaphragmatic arterioles in the rat is predominantly mediated by the A1AR, via the release of NO and activation of the ATP‐dependent K+ channels.