bluuebunny/crossref_metadata_2025_split huggingface dataset:
Self‐limiting enhancement by nitric oxide of oxygen free radical‐induced endothelial cell injury: evidence against the dual action of NO as hydroxyl radical donor/scavenger
Authors: Az‐Ma Toshiharu , Fujii Kohyu , Yuge Osafumi 
Published: July 2012

The effects of oxygen free radical scavengers and endothelial cell‐derived nitric oxide (EDNO) on the death of porcine cultured aortic endothelial cells exposed to exogenous superoxide‐ [xanthine (0.4 mM)/xanthine oxidase (0.04 unit ml−1) + diethylenetriaminepentaacetic acid (DTPA, 10 μm)] or hydroxyl radical‐generating system(s) [superoxide generating system + ferric iron (Fe3+, 0.1 mM) or peroxynitrite (0–100 μm)] have been evaluated.
Spin trapping studies using 5,5‐dimethyl‐1‐pyrroline‐N‐oxide (DMPO) with electron paramagnetic resonance spectrometry were also conducted to determine qualitatively the oxidant species generated by the oxidant generating systems.
Endothelial cell injury provoked by the exogenous superoxide generating system was inhibited by catalase, DTPA and a hydroxyl radical scavenger (dimethyl sulphoxide, DMSO), but not by superoxide dismutase (SOD). Addition of Fe3+ to the superoxide generating system enhanced the cell injury. These suggested that the direct cytotoxicity of exogenous superoxide is limited, and that endogenous transition metal‐dependent hydroxyl radical formation is involved in the cell injury.
An inhibitor of the constitutive NO‐pathway, NG‐monomethyl‐L‐arginine, did not influence cell injury induced by the superoxide generating system, suggesting that basal NO production is not responsible for the cytotoxicity.
Stimulation of endothelial cells with bradykinin enhanced cell injury provoked by the exogenous superoxide generating system, but not by the exogenous hydroxyl radical generating system. The enhancement by bradykinin was inhibited by NG‐monomethyl‐L‐arginine and bradykinin B2‐receptor antagonist, D‐Arg‐[Hyp3, Thi5, 8, D‐Phe7] bradykinin, suggesting that an interaction of NO with superoxide is involved in the enhanced cytotoxicity. A possible intermediate of this reaction, peroxynitrite, also caused endothelial cell injury in a concentration‐dependent manner.
The modulatory effects of NO on hydroxyl radical‐like activity (= formaldehyde production) from the superoxide generating system was also evaluated in a cell‐free superoxide/NO generating system, consisting of xanthine/xanthine oxidase, DTPA, DMSO, and various amounts of a spontaneous NO generator, sodium nitroprusside (SNP) and were compared with those of Fe3+. At doses up to 10 μm, SNP concentration‐dependently increased the formaldehyde production while the higher concentrations of SNP decreased. The maximum amount of formaldehyde produced by SNP was 5 fold less than that produced by Fe3+ (0.1 mM). Peroxynitrite‐induced formaldehyde formation was concentration‐dependently inhibited by SNP.
We conclude that agonist‐stimulated but not basal NO production acts as cytotoxic hydroxyl radical donor as well as the endogenous transition metal when endothelial cells are exposed to exogenous superoxide anion, while the modulatory effect of EDNO is limited by a secondary reaction with hydroxyl radicals.
The inhibitory effects of iberiotoxin and 4‐aminopyridine on the relaxation induced by β1‐ and β2‐adrenoceptor activation in rat aortic rings
Authors: Satake N. , Shibata M. , Shibata S. 
Published: July 2012

In rat aortic rings contracted by phenylephrine, the relaxation induced by isoprenaline was partly inhibited by iberiotoxin, (ibTX), tetraethylammonium, 4‐aminopyridine (4‐AP) and 1,9‐dideoxyforskolin, but not by glibenclamide.
In the presence of 4‐AP, 1,9‐dideoxyforskolin failed to inhibit further the relaxant response to isoprenaline. Cromakalim‐induced relaxation was inhibited by glibenclamide.
In the absence of endothelium, ibTX and 4‐AP still inhibited the relaxant response to isoprenaline.
The inhibitory effect of ibTX on the relaxant response to isoprenaline was eliminated by pretreatment with ICI‐118,551, a β2‐adrenoceptor antagonist, but not by atenolol, a β1‐adrenoceptor antagonist.
The inhibitory effect of 4‐AP on the relaxation induced by isoprenaline was abolished by atenolol, but not by ICI‐118, 551.
The inhibitory effect of ibTX on the isoprenaline‐induced relaxation in the presence of atenolol was completely abolished by MDL 12,330A, an adenylate cyclase inhibitor. Further, the inhibitory effect of 4‐AP on the isoprenaline‐induced relaxation in the presence of ICI‐118,551 was markedly reduced by MDL 12,330A.
The relaxation induced by dibutyryl cyclic AMP was partly inhibited by 4‐AP but not by ibTX. However, in the presence of KT5720, an inhibitor of cyclic AMP‐dependent protein kinase, ibTX failed to inhibit further the relaxation induced by isoprenaline.
These results suggest that, in rat aortic rings, Kca channels are involved in the relaxation induced by isoprenaline. In addition, Kca channels are mainly activated by β2‐adrenoceptors through cyclic AMP‐dependent pathways. Further, the inhibition of isoprenaline‐relaxation by 4‐AP may be related to the activation of β1‐adrenoceptors and cyclic AMP formation.
Changes in superoxide dismutase mRNA expression by streptozotocin‐induced diabetes
Authors: Kamata Katsuo , Kobayashi Tsuneo 
Published: July 2012

Experiments were designed to investigate the involvement of superoxide anions in the attenuated endothelium‐dependent relaxation of the rat aorta from streptozotocin (STZ)‐induced diabetic rats.
The endothelium‐dependent relaxation responses to acetylcholine (ACh, 10−7 m) in helical strips of the aorta precontracted with noradrenaline (NA, 5 × 10−8∼3 × 10−7 m) were significantly decreased in STZ‐induced diabetic rats. The recovery phase of the relaxation after single administration of ACh in the STZ‐induced diabetic rats was more rapid than those in control vessels.
Preincubation of aortic strips with superoxide dismutase (SOD, 60 u ml−1) normalized the recovery phase of the relaxation of diabetic aorta after single administration of ACh, whereas catalase (150 u ml−1) or indomethacin (10−5 m) had no effects on the relaxation.
SOD (180 u ml−1) caused relaxation in NA precontracted aortic strips and the degree of the SOD‐induced relaxation was significantly greater in diabetic aorta as compared with age‐matched control vessels.
When the changes in mRNA expressions of Mn‐SOD or Cu‐Zn‐SOD were observed, Mn‐SOD mRNA expression was markedly decreased, and Cu‐Zn‐SOD was slightly decreased in diabetic aorta.
These results suggest that the rapid destruction of NO by superoxide anions may occur in the STZ‐induced diabetic rats, and this may be due to a decrease in mRNA expression of Mn‐SOD or Cu‐Zn‐SOD.
PK 11195 blockade of benzodiazepine‐induced inhibition of forskolin‐stimulated adenylate cyclase activity in the striatum
Authors: Tenn Catherine C. , Neu John M. , Niles Lennard P. 
Published: July 2012

The effects of benzodiazepine receptor antagonists on the inhibition of forskolin‐stimulated adenylate cyclase (AC) activity by various benzodiazepine (BZ) and indoleamine agonists in the rat striatum were investigated.
A biphasic inhibition of forskolin‐stimulated AC activity by the peripheral‐type agonist, Ro5‐4864, and a multiphasic inhibition by the non‐selective BZ, diazepam, was observed. One phase of AC inhibition is consistent with a Gi‐coupled receptor‐mediated action, whereas the other phases appear to involve a direct effect on the enzyme itself.
While the central‐type antagonist, flumazenil, had no effect on the ability of Ro5‐4864 to inhibit AC activity, the peripheral‐type receptor ligand, PK 11195, abolished the first phase of inhibition.
PK 11195 and pertussis toxin were found to block the inhibitory effect of various BZs and the indoleamines, melatonin and 2‐iodomelatonin, on induced AC activity.
Saturation binding studies, conducted at 30°C with [3H]‐diazepam revealed a single binding site in the rat striatum (KD = 19.3 ± 0.80 nM) which significantly decreased in affinity in the presence of GTP (KD = 30.5 ± 2.6 nM; P < 0.05). No significant change in Bmax was observed.
These findings indicate the presence of Gi‐coupled BZ receptors in the rat striatum. Thus, suppression of cyclic AMP production may contribute to the diverse neuropharmacological effects of BZs, melatonin and related drugs.
Evidence of differential effects produced by ethanol on specific phospholipid biosynthetic pathways in rat hepatocytes
Authors: Carrasco María P. , Sanchez‐Amate María C. , Marco Carmen , Segovia Josefa L. 
Published: July 2012

The aim of the present study was to investigate the effects of ethanol in vitro on the phospholipid biosynthetic pathways in hepatocytes isolated from the rat. We have used [methyl‐14C]‐choline, [1‐3H]‐ethanolamine and L‐[3‐3H]‐serine as exogenous precursors of the corresponding phospholipids, phosphatidylcholine (PC), phosphatidylethanolamine (PE) and phosphatidylserine (PS).
Incubation of hepatocytes in the presence of ethanol significantly alters the incorporation of radiolabel from [14C]‐choline and [3H]‐ethanolamine into the metabolic intermediates and the final products of the CDP‐choline and CDP‐ethanolamine pathways. Radioactivity in the metabolic intermediates of both pathways was significantly decreased and the amount of label in PE was reduced whilst that of PC was not modified.
In the presence of 4‐methylpyrazole, an inhibitor of alcohol dehydrogenase (ADH) activity, ethanol produces a reduction in the label of choline phosphate, ethanolamine phosphate and a significant decrease in the amount of PC and PE radiolabel.
On the other hand, ethanol increases the incorporation of serine into phosphatidylserine, phosphatidylethanolamine and phosphatidylcholine, although this effect is observed only in the absence of 4‐methylpyrazole, indicating that this alteration is produced by some metabolite generated as a consequence of hepatic alcohol metabolism.
Ethanol also interferes with the methylation of phosphatidylethanolamine produced via the CDP‐ethanolamine pathway but it does not alter phosphatidylethanolamine methylation when this phospholipid is produced by mitochondrial phosphatidylserine decarboxylation, suggesting the existence of different intramembrane pools of phosphatidylethanolamine, which may exhibit different sensitivity to alcohol.
Our results indicate that ethanol exerts two different effects on phospholipid metabolism in hepatocytes: a stimulatory effect on the incorporation of exogenous substrates into different phospholipids probably related to an alteration in the availability of lipogenic substrates as a consequence of ethanol metabolism, and another inhibitory effect produced by ethanol per se, which can be observed only when ethanol metabolism is inhibited by the presence of a specific inhibitor of alcohol dehydrogenase activity.
The stimulation of capsaicin‐sensitive neurones in a vanilloid receptor‐mediated fashion by pungent terpenoids possessing an unsaturated 1,4‐dialdehyde moiety
Authors: Szallasi A. , Jonassohn M. , Ács G. , Bíró T. , Ács P. , Blumberg P.M. , Sterner O. 
Published: July 2012

The irritant fungal terpenoid isovelleral caused protective eye‐wiping movements in the rat upon intraocular instillation and showed cross‐tachyphylaxis with capsaicin, the pungent principle in hot pepper.
Isovelleral induced a dose‐dependent calcium uptake by rat dorsal root ganglion neurones cultured in vitro with an EC50 of 95 nM, which was fully inhibited by the competitive vanilloid receptor antagonist capsazepine.
Isovelleral inhibited specific binding of [3H]‐resiniferatoxin (RTX), an ultrapotent capsaicin analogue, to rat trigeminal ganglion or spinal cord preparations with an IC50 of 5.2 μm; in experiments in which the concentration of [3H]‐RTX was varied, isovelleral changed both the apparent affinity (from 16 pM to 37 pM) and the co‐operativity index (from 2.1 to 1.5), but not the Bmax.
The affinity of isovelleral for inducing calcium uptake or inhibiting RTX binding was in very good agreement with the threshold dose (2.2. nmol) at which it provoked pungency on the human tongue.
For a series of 14 terpenoids with an unsaturated 1,4‐dialdehyde, a good correlation was found between pungency on the human tongue and affinity for vanilloid receptors on the rat spinal cord.
The results suggest that isovelleral‐like compounds produce their irritant effect by interacting with vanilloid receptors on capsaicin‐sensitive sensory neurones. Since these pungent diterpenes are structurally distinct from the known classes of vanilloids, these data provide new insights into structure‐activity relations and may afford new opportunities for the development of drugs targeting capsaicin‐sensitive pathways.
Attenuation by prolonged nitric oxide synthase inhibition of the enhancement of fibrinolysis caused by environmental stress in the rat
Authors: Kawabata Atsufumi , Hata Taeko 
Published: July 2012

Nitric oxide (NO) suppresses platelet aggregation and plasminogen activator inhibitor (PAI) release from platelets, playing physiological and/or pathological roles in the haemostatic system. We investigated the effect of NG‐nitro‐L‐arginine methyl ester (L‐NAME), an NO synthase inhibitor, on the disseminated intravascular coagulation (DIC)‐like phenomena in rats under environmental stress, induced by prolonged fluctuation in air temperature, known as SART (specific alternation of rhythm in temperature) stress.
Exposure of rats to SART stress for 7 days caused mild DIC‐like symptoms such as thrombocytopenia, hypofibrinogenemia, decreased factor VIII: coagulant activity and shortened euglobulin clot lysis time (ECLT). The enhanced fibrinolysis was accompanied by a marked decrease in the activity of plasma PAI.
L‐NAME, but not its D‐enantiomer, when administered orally at 0.3–10 mg kg−1, twice a day for 7‐day exposure to stress, inhibited the stress‐induced decrease in fibrinogen levels in a dose‐dependent manner, whereas it failed to alter platelet count, factor VIII:coagulant activity and plasma protein levels in stressed rats. All these parameters in unstressed rats were resistant to L‐NAME at 10 mg kg−1.
Repeated treatment with 10 mg kg−1 of L‐NAME blocked the shortening of ECLT and the decrease in PAI activity following stress exposure, although it was without effect in unstressed rats.
The inhibitory effects of L‐NAME at 10 mg kg−1 on the stress‐induced alterations in fibrinogen levels and in ECLT were significantly reduced by coadministered L‐arginine at 1000 mg kg−1.
These findings demonstrate that repeated administration of L‐NAME attenuates the enhanced fibrinolysis, without aggravating thrombocytopenia, in SART‐stressed rats. Endogenous NO appears to contribute to the stress‐induced development of fibrinolysis by suppressing plasma PAI activity, most probably as a result of inhibition of the PAI release from platelets.
Tachykinin inhibition of acid‐induced gastric hyperaemia in the rat
Authors: Heinemann Akos , Jocic Milana , Herzeg Gemot , Holzer Peter 
Published: July 2012

Primary afferent neurones releasing the vasodilator, calcitonin gene‐related peptide, mediate the gastric hyperaemic response to acid back‐diffusion. The tachykinins neurokinin A (NKA) and substance P (SP) are located in the same neurones and are co‐released with calcitonin gene‐related peptide. In this study we investigated the effect and possible role of tachykinins in the acid‐evoked gastric vasodilatation in urethane‐anaesthetized rats.
Gastric acid back‐diffusion, induced by perfusing the stomach with 15% ethanol in the presence of 0.05 m HCl, increased gastric mucosal blood flow by 60–90%, as determined by the hydrogen clearance technique. NKA and SP (0.14‐3.78 nmol min−1 kg−1, infused intra‐aortically) inhibited the gastric mucosal hyperaemic response to acid back‐diffusion in a dose‐dependent manner, an effect that was accompanied by aggravation of ethanol/acid‐induced macroscopic haemorrhagic lesions.
The inhibitory effect of NKA (1.26 nmol min−1 kg−1) on the acid‐induced gastric mucosal vasodilatation was prevented by the tachykinin NK2 receptor antagonist, MEN 10,627 (200 nmol kg−1) but left unaltered by the NK1 receptor antagonist, SR 140,333 (300 nmol kg−1) and the mast‐cell stabilizer, ketotifen (4.6 μmol kg−1).
Under basal conditions, with 0.05 m HCl being perfused through the stomach, NKA (1.26 nmol min−1 kg−1) reduced gastric mucosal blood flow by about 25%, an effect that was abolished by SR 140,333 but not MEN 10,627 or ketotifen.
SR 140,333, MEN 10,627 or ketotifen had no significant effect on basal gastric mucosal blood flow nor did they modify the gastric mucosal hyperaemic reaction to acid back‐diffusion.
The effect of NKA (1.26 nmol min−1 kg−1) in causing vasoconstriction and inhibiting the vasodilator response to acid back‐diffusion was also seen when blood flow in the left gastric artery was measured with the ultrasonic transit time shift technique.
Arginine vasopressin (AVP, 0.1 nmol min−1 kg−1) induced gastric mucosal vasoconstriction under basal conditions but was unable to inhibit the dilator response to acid back‐diffusion.
These data show that NKA has two fundamentally different effects on the gastric circulation. Firstly, NKA reduces gastric blood flow by activation of NK1 receptors. Secondly, NKA inhibits the gastric hyperaemic response to acid back‐diffusion through an NK2 receptor‐mediated mechanism. These two tachykinin effects appear to take place independently of each other since they are mediated by different receptors. This concept is further supported by the inability of AVP to mimic tachykinin inhibition of the gastric vasodilator response to acid back‐diffusion.
Actions of picrodendrin antagonists on dieldrin‐sensitive and ‐resistant Drosophila GABA receptors
Authors: Hosie Alastair M. , Ozoe Yoshihisa , Koike Kazuo , Ohmoto Taichi , Nikaido Tamotsu , Sattelle David B. 
Published: July 2012

A series of terpenoid compounds, recently isolated from Picrodendron baccatum, share a picrotoxane skeleton with picrotoxinin, an antagonist of ionotropic GABA receptors. Referred to as picrodendrins, they inhibit the binding of [35S]‐tert‐butylbicyclophosphorothionate (TBPS) to rat GABAA receptors. Hitherto, their effects on GABA receptors have not been investigated electrophysiologically. Under two‐electrode voltage‐clamp, the actions of picrodendrins and related terpenoids have been assayed on homo‐oligomeric GABA receptors formed by the expression of a Drosophila GABA receptor subunit (RDLac) in Xenopus oocytes.
All the terpenoids tested, dose‐dependently antagonized currents induced by 30 μm (EC50) GABA.
Tutin and its analogues (dihydrotutin and isohyenanchin) differ in the structure of their axial C4 substituents. Of these compounds, tutin, which bears an isopropenyl group at this carbon atom, was the most potent antagonist of RDLac homo‐oligomers, whereas isohyenanchin, which bears a hydroxyisopropyl group, was the least potent antagonist tested.
Picrodendrins differ mainly in the structure of their C9 substituents. The IC50s of picrodendrins ranged from 17 ± 1.3 nM (picrodendrin‐Q) to 1006 ± 1.3 nM (picrodendrin‐O). As such, the most potent picrodendrins (Q, A and B) were approximately equipotent with picrotoxinin as antagonists of RDLac homo‐oligomers.
Certain picrodendrin compounds effected a use‐dependent blockade of RDLac homo‐oligomers. Such a biphasic block was not observed with tutin analogues.
Picrotoxin‐resistant RDLacA3025 homo‐oligomers, which have a single amino acid substitution (A302S) in the 2nd transmembrane region, were markedly less sensitive to picrodendrin‐O than the wild‐type, dieldrin‐sensitive, homo‐oligomers.
The relative potency of tutin analogues demonstrates that the structure‐activity relationship of the C4 substituent of picrotoxane‐based compounds is conserved in vertebrates and insects. However, the relative order of potency of picrodendrins on RDLac homo‐oligomers is distinctly different from that observed in previous radioligand binding studies performed on vertebrate GABAA receptors. As picrodendrin compounds differ in the structure of their C9 substituents, these data suggest that the optimal convulsant pharmacophores of vertebrate GABAA receptors and RDLac homo‐oligomers differ with respect to this substituent.
Agonist pharmacology of two Drosophila GABA receptor splice variants
Authors: Hosie Alastair M. , Sattelle David B. 
Published: July 2012

The Drosophila melanogaster γ‐aminobutyric acid (GABA) receptor subunits, RDLac and DRC 17‐1‐2, form functional homo‐oligomeric receptors when heterologously expressed in Xenopus laevis oocytes. The subunits differ in only 17 amino acids, principally in regions of the N‐terminal domain which determine agonist pharmacology in vertebrate ionotropic neurotransmitter receptors. A range of conformationally restricted GABA analogues were tested on the two homo‐oligomers and their agonist pharmacology compared with that of insect and vertebrate iontropic GABA receptors.
The actions of GABA, isoguvacine and isonipecotic acid on RDLac and DRC 17‐1‐2 homo‐oligomers were compared, by use of two‐electrode voltage‐clamp. All three compounds were full agonists of both receptors, but were 4–6 fold less potent agonists of DRC 17‐1‐2 homo‐oligomers than of RDLac. However, the relative potencies of these agonists on each receptor were very similar.
A more complete agonist profile was established for RDLac homo‐oligomers. The most potent agonists of these receptors were GABA, muscimol and trans‐aminocrotonic acid (TACA), which were approximately equipotent. RDLac homo‐oligomers were fully activated by a range of GABA analogues, with the order of potency: GABA>ZAPA ((Z)‐3‐[(aminoiminomethyl)thio]prop‐2‐enoic acid) > isoguvacine > imidazole‐4‐acetic acid ≥ isonipecotic acid ≥ cis‐aminocrotonic acid (CACA) > β‐alanine. 3‐Aminopropane sulphonic acid (3‐APS), a partial agonist of RDLac homo‐oligomers, was the weakest agonist tested and 100 fold less potent than GABA.
SR95531, an antagonist of vertebrate GABAA receptors, competitively inhibited the GABA responses of RDLac homo‐oligomers, which have previously been found to be insensitive to bicuculline. However, its potency (IC50 500 μm was much reduced when compared to GABAA receptors.
The agonist pharmacology of Drosophila RDLac homo‐oligomers exhibits aspects of the characteristic pharmacology of certain native insect GABA receptors which distinguish them from vertebrate GABA receptors. The high potency and efficacy of isoguvacine and ZAPA distinguishes RDLac homo‐oligomers from bicuculline‐insensitive vertebrate GABAC receptors, while the low potency of SR95531 and 3‐APS distinguishes them from GABAA receptors. The differences in the potency of agonists on RDLac and DRC 17‐1‐2 homo‐oligomers observed in the present study may assist in identification of further molecular determinants of GABA receptor function.