bluuebunny/crossref_metadata_2025_split huggingface dataset:
Carbon monoxide‐induced vasorelaxation and the underlying mechanisms
Authors: Wang Rui , Wang Zunzhe , Wu Lingyun 
Published: August 2006

Carbon monoxide (CO) induced a concentration‐dependent relaxation of isolated rat tail artery tissues which were precontracted with phenylephrine or U‐46619. This vasorelaxing effect of CO was independent of the presence of the intact endothelium.
The CO‐induced vasorelaxation was partially inhibited by the blockade of either the cyclicGMP pathway or big‐conductance calcium‐activated K (KCa) channels. When both the cyclicGMP pathway and KCa channels were blocked, the CO‐induced vasorelaxation was completely abolished.
Incubation of vascular tissues with hemin, in order to enhance the endogenous production of CO, suppressed the phenylephrine‐induced vasocontraction in a time‐ and concentration‐dependent manner. The hemin‐induced suppression of the vascular contractile response to phenylephrine was abolished after the vascular tissues were co‐incubated with either oxyhaemoglobin or zinc protoporphyrin‐IX, suggesting an induced endogenous generation of CO from vascular tissues.
The effect of hemin incubation on vascular contractility did not involve the endogenous generation of nitric oxide.
Our results suggest that CO may activate both a cyclicGMP signalling pathway and KCa channels in the same vascular tissues, and that the endogenously generated CO may significantly affect the vascular contractile responses.
Renal effects of intrathecally injected tachykinins in the conscious saline‐loaded rat: receptor and mechanism of action
Authors: Ding Yuan Yi , Couture Réjean 
Published: August 2006

The effects of intrathecally (i.t.) injected substance P (SP), neurokinin A (NKA), [β‐Ala8]NKA (4–10) and [MePhe7]neurokinin B (NKB) at T13 thoracic spinal cord level were investigated on renal excretion of water, sodium and potassium in the conscious saline‐loaded rat. Antagonists selective for NK1 (RP 67580), NK2 (SR 48968) and NK3 (R 820; 3‐indolylcarbonyl‐Hyp‐Phg‐N(Me)‐Bzl) receptors were used to characterize the spinal effect of SP on renal function.
Saline gavage (4.5% of the body weight) enhanced renal excretion of water, sodium and potassium over the subsequent hour of measurement. Whereas these renal responses were not affected by 0.65nmol SP, the dose of 6.5 nmol SP blocked the natriuretic response (aCSF value 3.9±0.8; SP value 0.7±0.3μmolmin−1, P<0.01) as well as the renal excretion of water (aCSF value 48.9±5.8; SP value 14.5±4.0μlmin−1, P<0.01) and potassium (aCSF value 4.8±0.6; SP value 1.5±0.6μmolmin−1, P<0.01) at 30min post‐injection. SP had no significant effect on urinary osmolality. The SP‐induced renal inhibitory effects during the first 30min were abolished in rats subjected to bilateral renal denervation 1 week earlier or in rats injected i.t. 5min earlier with 6.5nmol RP 67580. In contrast, the co‐injection of SR 48968 and R 820 (6.5nmol each) did not affect the inhibitory responses to SP. On their own, these antagonists had no direct effect on renal excretion function. Since SP induced only transient changes in mean arterial blood pressure (−18.8±3.8mmHg at 1min and +6.3±2.4mmHg at 5min post‐injection), it is unlikely that the renal effects of SP are due to systemic haemodynamic changes.
NKA (6.5nmol but not 0.65nmol) produced a transient drop in renal excretion of water (aCSF value 31.2±5.1; NKA value 11.3±4.2μlmin−1, P<0.05), sodium (aCSF value 1.7±0.8; NKA value 0.4±0.2μmolmin−1, P<0.05) and potassium (aCSF value 4.1±0.7; NKA value 1.5±0.4μmolmin−1, P<0.05) at 15min post‐injection. However, the same doses (6.5nmol) of selective agonists for tachykinin NK2 ([β‐Ala8]NKA(4–10)) and NK3 ([MePhe7]NKB) receptors were devoid of renal effects.
This study provided functional evidence that tachykinins may be involved in the renal control of water and electrolyte excretion at the level of the rat spinal cord through the activation of NK1 receptors and the sympathetic renal nerve.
Voltage and pH dependent block of cloned N‐type Ca2+ channels by amlodipine
Authors: Furukawa Taiji , Nukada Toshihide , Suzuki Kazuyuki , Fujita Yoshihiko , Mori Yasuo , Nishimura Masao , Yamanaka Masami 
Published: August 2006

Two types of Ca2+ channel α1‐subunits were co‐expressed in Xenopus oocytes with the Ca2+ channel α2‐ and β1‐subunits. The Ba2+ current through the α1Cα2β and the α1Bα2β channels had electrophysiological and pharmacological properties of L‐ and N‐type Ca2+ channels, respectively.
Amlodipine had a strong blocking action on both the L‐type and N‐type Ca2+ channels expressed in the oocyte. The potency of the amlodipine block on the N‐type Ca2+ channel was comparable to that on the L‐type Ca2+ channel. At −100mV holding potential, the IC50 values for amlodipine block on the L‐type and N‐type Ca2+ channel were 2.4 and 5.8μm, respectively.
The blocking action of amlodipine on the N‐type Ca2+ channel was dependent on holding potential and extracellular pH, as has been observed with amlodipine block on the L‐type Ca2+ channel. A depolarized holding potential and high pH enhanced the blocking action of amlodipine.
The time course of block development by amlodipine was similar for L‐type and N‐type Ca2+ channels. However, it was slower than the time course of block development by nifedipine for the L‐type Ca2+ channel.
Down‐regulation of the hepatic cytochrome P450 by an acute inflammatory reaction: implication of mediators in human and animal serum and in the liver
Authors: El‐Kadi Ayman O S , Maurice Hélène , Ong Huy , du Souich Patrick 
Published: August 2006

Infection and inflammation trigger a cascade of mediators that eventually will down‐regulate the hepatic cytochrome P450 (P450). The present study aimed to characterize the mediators contained in the serum of rabbits with an acute inflammatory reaction (AIR) induced by the s.c. injection of turpentine (5ml), and in the serum of humans with an acute upper respiratory tract viral infection.
Hepatocytes from control (HCONT) rabbits and rabbits with an AIR (HINFLA) were isolated and cultured. Compared with HCONT in HINFLA the production of theophylline metabolites, 3‐methylxanthine (3MX), 1‐methyluric acid (1MU), and 1,3‐dimethyluric acid (1,3DMU) was reduced as was the amount of total P450, while lipid peroxidation was increased. Incubation of HINFLA with serum of rabbits with an AIR (RSINFLA) for 4h further reduced the formation of the metabolites of theophylline as well as the amount of P450, and enhanced the lipid peroxidation. RSINFLA obtained 6, 12 and 24h after the injection of turpentine showed the same ability to down‐regulate hepatic P450 as the serum obtained at 48h.
The efficacy (Emax) of RSINFLA to inhibit the formation of theophylline metabolites differed, i.e. 1,3DMU>1MU>3MX, and the potency of serum mediators (IC50) was similar for 3MX and 1MU, but lower for 1,3DMU.
Incubation of serum of human volunteers (HSINFLA) with a viral infection with HCONT or HINFLA reduced the production of theophylline metabolites, as well as the amount of P450, and increased the lipid peroxidation. HSINFLA depressed 1,3DMU more efficiently than 3MX and 1MU. HSINFLA reduced 3MX with greater efficacy than did RSINFLA. Potency was very variable but not different from rabbits.
It is concluded that the serum of rabbits with an AIR or of humans with a viral infection contain several mediators that inhibit noncompetitively various isoenzymes of the hepatic P450. The decrease in P450 induced by HSINFLA or RSINFLA is closely associated with the increase in lipid peroxidation (r2=0.8870) suggesting that lipid peroxidation could directly or indirectly be involved in the P450 down‐regulation.
Pharmacological characterization of type 1α metabotropic glutamate receptor‐stimulated [35S]‐GTPγS binding
Authors: Akam Elizabeth C , Carruthers Alan M , Nahorski Stefan R , John Challiss R A 
Published: August 2006

The activation of G proteins by type 1α metabotropic glutamate receptors (mGluRs) in membranes from recombinant baby hamster kidney cells expressing the cloned rat mGluR1α receptor has been studied by use of a [35S]‐guanosine 5′‐[γ‐thio]triphosphate ([35S]‐GTPγS) binding assay.
l‐Glutamate increased the rate of [35S]‐GTPγS binding in a concentration‐dependent manner (−logEC50 (m) 5.25±0.07), with an optimal (62.4±1.6%) increase over basal binding being observed following 60min incubation at 30°C with 70pm [35S]‐GTPγS, 1μmGDP, 10mmMgCl2, 100mm NaCl and 100μg membrane proteinml−1. The l‐glutamate (100μm)‐stimulated increase in [35S]‐GTPγS binding was totally prevented in the presence of the group I mGluR antagonist (S)‐4‐carboxy‐3‐hydroxyphenylglycine (300μm).
Quantitative analysis of the affinity and number of G proteins activated by a maximally effective concentration of l‐glutamate revealed an equilibrium dissociation constant (KD) for [35S]‐GTPγS binding of 0.76±0.20nm and a maximal number of GTPγS‐liganded G proteins (Bmax) of 361±30fmol mg−1 protein.
Metabotropic glutamate receptor agonists, quisqualate (−logEC50 (m) 6.74±0.06), 1S,3R‐ACPD (4.64±0.08) and (S)‐3,5‐dihydroxyphenylglycine (5.16±0.23) also increased [35S]‐GTPγS binding in a concentration‐dependent manner, with the latter two agents behaving as partial agonists.
(+)‐α‐Methylcarboxyphenylglycine (300μm) caused a parallel rightward shift of the l‐glutamate concentration‐effect curve for [35S]‐GTPγS binding, allowing an antagonist equilibrium dissociation constant (KD) of 34.0±7.8μm to be calculated for this mGluR antagonist.
Pretreatment of BHK‐mGluR1α cells with a concentration of pertussis toxin (PTX) shown to be maximally effective (100ngml−1, 24h) before membrane preparation resulted in a marked decrease in agonist‐stimulated [35S]‐GTPγS binding (by 66.0±0.9%), and an altered concentration‐effect relationship for agonist‐stimulated [35S]‐GTPγS binding by the residual PTX‐insensitive G‐protein population.
The modulation of [35S]‐GTPγS binding by agonists and antagonists in membranes from recombinant cells provides an excellent system in which to study mGluR interactions with PTX‐sensitive and ‐insensitive G proteins.
Inducible nitric oxide synthase after sensitization and allergen challenge of Brown Norway rat lung
Authors: Fang Liu Shu , Haddad El‐Bdaoui , Adcock Ian , Salmon Michael , Koto Hiro , Gilbey Tom , Barnes Peter J , Fan Chung K 
Published: August 2006

We studied the effects of ovalbumin (OA) sensitization and challenge on inducible nitric oxide synthase (iNOS) gene and protein expression in Brown‐Norway rats in vivo.
By use of Northern analysis, a 4.4‐kb iNOS mRNA transcript was weakly observed in control rat lung but there was a 3 fold increase in lungs sensitized to OA alone (P<0.05). In sensitized rats, four hours after exposure to OA aerosol, there was a 6 fold increase in iNOS mRNA transcript (P<0.05), which returned to baseline at 24 h.
Immunostaining with an anti‐mouse iNOS antibody revealed some patchy staining of airway epithelium in naïve rats. There were no changes in sensitized rats exposed to saline, but sensitized and OA‐exposed rats showed increased expression in iNOS staining in macrophages.
Electrophoretic mobility shift assays of lung nuclear extracts showed a marked increase in nuclear factor‐κB (NF‐κB)‐binding activity at 2 h after allergen exposure with return to baseline at 6, 12 and 24 h.
We concluded that there is increased iNOS gene and protein expression associated with increased NF‐κB DNA‐binding in lungs of sensitized and challenged rats. The increase in iNOS expression may underlie the increase in exhaled NO found after allergen challenge and may contribute to the development of allergen‐induced airway hyperresponsiveness.
Inherent tone of human bronchus: role of eicosanoids and the epithelium
Authors: Watson N , Magnussen H , Rabe K F 
Published: August 2006

Airway preparations of different species possess varying degrees of inherent tone which is the result of different metabolites of arachidonic acid in different species. In human bronchial smooth muscle in vitro we have investigated the effects of 5‐lipoxygenase inhibition (zileuton, 10μm), cyclo‐oxygenase inhibition (indomethacin, 1μm) and mechanical epithelium removal on inherent tone. The shunting of arachidonic acid by inhibition of one or other of these enzymes, as a possible explanation for the effects observed, has also been investigated.
Zileuton caused a significant fall in tone either alone (−107±33mg) or after cyclo‐oxygenase inhibition (−203±48mg) and this effect was not significantly altered by epithelial removal (−191±43mg alone; −333±88mg after indomethacin). Indomethacin increased tone when applied alone (160±94mg), but this effect only reached statistical significance after 5‐lipoxygenase inhibition, (210±81mg; P<0.05). Epithelial removal did not alter the effect of indomethacin when applied alone (213±97mg), but significantly reduced the effect of indomethacin after 5‐lipoxygenase inhibition (34±23mg; P<0.05).
These data suggest that inherent tone in human bronchus is largely the result of contractile 5‐lipoxygenase products. However, the involvement of cyclo‐oxygenase products cannot entirely be discounted, since in the presence of 5‐lipoxygenase inhibition contractile and relaxant eicosanoids originating from the bronchial epithelium appear to influence significantly inherent tone.
Effects of dopamine on L‐type Ca2+ current in single atrial and ventricular myocytes of the rat
Authors: Zhao H , Matsuoka S , Fujioka Y , Noma A 
Published: August 2006

The effects of dopamine on the L‐type Ca2+ current (ICa,L) of both atrial and ventricular single myocytes and on the force of contraction of atrial trabeculae in rat heart were investigated.
Dopamine increased atrial ICa,L at concentrations higher than 1 μM, but had little or no effect on ICa,L at lower concentrations. The increase in ICa,L at high concentrations was reversed by propranolol and acetylcholine, but not by phentolamine. Activation and inactivation kinetics of ICa,L were not altered by dopamine.
In rat ventricular myocytes in which the D4 receptor mRNA does not express, dopamine (20–100 μM) also increased the ICa,L amplitude and propranolol reversed this effect.
Clozapine, a potent D4 receptor antagonist, blocked the augmenting effect of dopamine on ICa,L. However, this effect could be explained by β‐antagonism, since clozapine also inhibited the isoprenaline effect.
In the atrial trabeculae, the increase in contraction by dopamine (1 to 30 μM) was reversed by 1 μM propranolol, but not by 2 μM phentolamine. Low doses of dopamine (0.01 to 0.3 μM) did not affect the contraction in the controls or during a modest stimulation of the β‐adrenoceptor with 0.01 μM isoprenaline.
These results indicate that the positive inotropic action of dopamine is mediated through direct stimulation of the β‐adrenoceptor in both atrial and ventricular myocytes. Involvement of D4 receptor appears unlikely in the regulation of the atrial contraction.
Effects of the wasp venom peptide, mastoparan, on GTP hydrolysis in rat brain membranes
Authors: Odagaki Y , Nishi N , Koyama T 
Published: August 2006

The effects of mastoparan, a wasp venom toxin, on GTP hydrolyzing activity were examined in rat brain membranes.
Mastoparan inhibited the low‐affinity GTPase activity, defined as the amount of 32Pi released from 0.3 μM [γ‐32P]‐GTP in the presence of 100 μM unlabelled GTP, in a concentration‐dependent manner. This inhibitory effect of mastoparan on low‐affinity GTPase activity was diminished by increasing concentrations of UDP and was completely attenuated at 20 mM, indicating that activation of nucleoside diphosphokinase (NDPK) is inolved in the phenomenon.
In the presence of 20 mM UDP, mastoparan stimulated the high‐affinity GTPase activity by increasing the Vmax value without affecting the apparent KM for GTP. Mastoparan‐stimulated high‐affinity GTPase activity was apparent at concentrations higher than 1 μM, in a concentration‐dependent manner, but without saturation even at 100 μM.
Mastoparan‐induced high‐affinity GTPase activity showed a characteristic sensitivity to MgCl2, quite different from that seen in L‐glutamate‐stimulated activity, a representative of receptor‐mediated G‐protein activation.
There appeared to be a simple additive interaction between mastoparan‐ and L‐glutamate‐stimulated high‐affinity GTPase activities, indicting that distinct pools of G‐proteins are involved in receptor‐independent and receptor‐mediated G‐protein activation.
These results suggest that G‐proteins in brain membranes are functionally altered by mastoparan through multiple mechanisms of action and that the mastoparan‐induced, direct G‐protein activating process lacks a synergistic or antagonistic interaction with an agonist‐induced, receptor‐mediated activation of G‐proteins.
Involvement of protein kinase C in reduced relaxant responses to the NO/cyclic GMP pathway in piglet pulmonary arteries contracted by the thromboxane A2‐mimetic U46619
Authors: Pérez‐Vizcaíno Francisco , Villamor Eduardo , Duarte Juan , Tamargo Juan 
Published: August 2006

Impairment of nitric oxide (NO)/cyclic GMP production and/or increased activities of thromboxane A2 (TXA2) and endothelin‐1 (ET‐1) have been associated with pulmonary hypertension. We have analysed the interactions of noradrenaline (NA), the TXA2‐mimetic U46619 and ET‐1 with the relaxation induced via cyclic GMP in isolated piglet intrapulmonary arteries.
The contractions induced by NA were augmented by endothelium removal or by methylene blue and pre‐contracted rings were fully relaxed by acetylcholine, sodium nitroprusside (SNP), atrial natriuretic peptide and 8‐bromo‐cyclic GMP. In contrast, U46619‐ and ET‐1 induced contractions were endothelium‐independent and only partially relaxed by the latter vasodilators. Whereas the reduced responses to SNP in arteries contracted by U46619 were independent of the U46619‐induced tone, a higher concentration of ET‐1 (tone higher than that induced by NA) was required to reduce the vasodilator responses to SNP. NA, U46619 and ET‐1 had no effect on the SNP‐induced increases in cyclic GMP.
The reduced relaxant responses to SNP in arteries pre‐contracted by U46619 were specific for piglet pulmonary arteries since they were not observed in piglet mesenteric or coronary arteries or in rat pulmonary arteries. Furthermore, there were no differences in the relaxant response to the adenylate cyclase activator forskolin in piglet pulmonary arteries pre‐contracted by either NA, U46619 or ET‐1.
SNP‐induced relaxation was inhibited by thapsigargin (but not by inhibition of the membrane Na+/K+ ATPase nor K+ channels) indicating a role for Ca2+ sequestration by the Ca2+ ATPase in the effects of SNP.
The phorbol ester 12‐myristate, 13‐acetate inhibited the relaxant response to SNP. The inhibitory effect of U46619 on SNP‐induced relaxation was abolished by the protein kinase C inhibitor (PKC) staurosporine suggesting that PKC may be a part of the signal transduction mechanism.
In summary, piglet pulmonary arteries when activated by a TXA2‐mimetic show abnormally reduced relaxant responses to the NO/cyclicGMP pathway. This effect appears to be mediated by activation of PKC.
Alterations in endothelium‐dependent hyperpolarization and relaxation in mesenteric arteries from streptozotocin‐induced diabetic rats
Authors: Fukao Mitsuhiro , Hattori Yuichi , Kanno Morio , Sakuma Ichiro , Kitabatake Akira 
Published: August 2006

The aim of this study was to determine whether endothelium‐dependent hyperpolarization and relaxation are altered during experimental diabetes mellitus. Membrane potentials were recorded in mesenteric arteries from rats with streptozotocin‐induced diabetes and age‐matched controls. The resting membrane potentials were not significantly different between control and diabetic mesenteric arteries (−55.3±0.5 vs −55.6±0.4 mV). However, endothelium‐dependent hyperpolarization produced by acetylcholine (ACh; 10−8–10−5 M) was significantly diminished in amplitude in diabetic arteries compared with that in controls (maximum −10.4±1.1 vs −17.2±0.8 mV). Furthermore, the hyperpolarizing responses of diabetic arteries were more transient.
ACh‐induced hyperpolarization observed in control and diabetic arteries remained unaltered even after treatment with 3×10−4 M NG‐nitro‐L‐arginine (L‐NOARG), 10−5 M indomethacin or 60 u ml−1 superoxide dismutase.
Endothelium‐dependent hyperpolarization with 10−6 M A23187, a calcium ionophore, was also decreased in diabetic arteries compared to controls (−8.3±1.4 vs −18.0±1.9 mV). However, endothelium‐independent hyperpolarizing responses to 10−6 M pinacidil, a potassium channel opener, were similar in control and diabetic arteries (−20.0±1.4 vs −19.2±1.1 mV).
The altered endothelium‐dependent hyperpolarizations in diabetic arteries were almost completely prevented by insulin therapy. Endothelium‐dependent relaxations by ACh in the presence of 10−4 M L‐NOARG and 10−5 M indomethacin in diabetic arteries were also reduced and more transient compared to controls.
These data indicate that endothelium‐dependent hyperpolarization is reduced by diabetes, and this would, in part, account for the impaired endothelium‐dependent relaxations in mesenteric arteries from diabetic rats.
Spatial heterogeneity of the effects of calcitonin gene‐related peptide (CGRP) on the microvasculature of ligaments in the rabbit knee joint
Authors: Ferrell W R , McDougall J J , Bray R C 
Published: August 2006

Experiments were performed in anaesthetized rabbits to examine the effects of calcitonin gene‐related peptide (CGRP) and the CGRP antagonist CGRP8–37 on blood flow to the medial collateral ligament of the knee joint.
Topical application of CGRP (10−13 to 10−9 mol) to the exposed external surface of eight knee joints resulted in dose‐dependent dilatation of vessels in both the ligament and the joint capsule. The magnitude of this response varied significantly in different regions of the medial collateral ligament, with the 10−9 mol dose of CGRP giving the maximum response (101.5±25.3% increase) at the femoral insertion site of the medial collateral ligament and lowest (23.1±8.8%) at the tibial insertion site.
Topical application of CGRP8–37 (0.1, 1 and 10 nmol) produced dose‐dependent constriction of vessels in the ligament and the joint capsule in five knees, with a trend towards the greatest effect occurring at the femoral insertion site (45.8±8.1% reduction in blood flow). With the 10 nmol dose, the vasoconstrictor response at the femoral insertion site differed significantly (P<0.05) from the responses obtained at the tibial insertion and joint capsule sites.
Topical application of CGRP8–37 (0.1, 1 and 10 nmol) to four chronically denervated knees produced substantially smaller vasoconstrictor responses at all sites. At the femoral insertion site, where 10 nmol CGRP8–37 normally produces a 45.8±8.1% reduction in blood flow (n=8), ten days following denervation this response was reduced to 6.5±6.1%, this difference being significant (P=0.01).
Adrenaline was applied topically to augment blood vessel tone, in order to establish how effectively co‐administration of CGRP would offset this increase in tone. Adrenaline (10−10 mol) produced vasoconstriction at all sites (n=6). In the capsule this vasoconstriction was virtually abolished when CGRP (10−9 mol) was co‐administered with adrenaline but in the ligament vasodilatation occurred at all sites. This vasodilatation was significantly greater at the femoral insertion site compared to the tibial insertion and mid ligament sites (P<0.05 for both) and the capsule (P<0.01).
Topical application of substance P (10−10 or 10−9 mol) failed to elicit dilatation of ligament blood vessels.
These results suggest that endogenous CGRP may play an important role in regulating blood flow to different structures in and around the knee joint.