bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ouabain‐induced increases in resting tone of human hyperplastic prostate following repeated noradrenaline and electrical field stimulation
Authors: Guh Jih‐Hwa , Ko Feng‐Nien , Chueh Shih‐Chieh , Lai Ming‐Kuen , Teng Che‐Ming 
Published: July 2012

The effect of ouabain on contractions to repeated noradrenaline stimulation and electrical field stimulation of human hyperplastic prostate was examined. Ouabain (1 μm) did not induce contractile response per se but progressively increased the resting tone (i.e., the tone between one noradrenaline stimulation, or electrical field stimulation, and the following) of human hyperplastic prostate.
The increased tone by ouabain following repeated noradrenaline stimulations or electrical field stimulation was fully relaxed by the removal of external calcium, and recovered following restoration of calcium.
The effect of noradrenaline on Na+ uptake was measured. Noradrenaline (10 μm) significantly increased the rate of Na+ accumulation in the presence of ouabain (1 μm); this stimulatory effect was almost completely blocked by prazosin (0.1 μm) and ethylisopropylamiloride (100 μm). In contrast, tetrodotoxin (1 μm) had no effect on noradrenaline‐stimulated Na+ transport in human hyperplastic prostate.
Intracellular Na+ loading by noradrenaline (10 μm) in the presence of ouabain (1 μm) significantly increased the transmembrane Ca2+ uptake as compared with the absence of ouabain; however, nifedipine (1 μm) was ineffective on Ca2+ uptake under this condition.
Transmembrane Ca2+ efflux was stimulated by noradrenaline (10 μm) in human hyperplastic prostate; this effect was significantly decreased in the presence of ouabain (1 μm).
It is suggested that the increased tone of human hyperplastic prostate following repeated excitation in the presence of ouabain is due to increased Ca2+ entry and reduced efflux of Ca2+ through the Na+/Ca+ exchange system as a consequence of Na+ pump inhibition by ouabain.
Metabolism of the macrolide immunosuppressant, tacrolimus, by the pig gut mucosa in the Ussing chamber
Authors: Lampen Alfonso , Christians Uwe , Gonschior Ann‐Katrin , Bader Augustinus , Hackbarth Ingelore , von Engelhardt Wolfgang , Sewing Karl‐Friedrich 
Published: July 2012

The macrolide tacrolimus (FK506), used as an immunosuppressant, is a cytochrome P450 (CYP) 3A substrate in the liver. The metabolism of tacrolimus and the transport of its metabolites in the pig gut was studied in the Ussing chamber. Tacrolimus and its metabolites were quantified by h.p.l.c./mass spectrometry.
In the Ussing chamber, demethyl, didemethyl, hydroxy and hydroxy‐demethyl tacrolimus were generated. Their formation was concentration‐ and time‐dependent. The metabolite pattern was not different from that after incubation of tacrolimus with human small intestinal microsomes.
The metabolite formation was highest in the duodenum and declined in the order duodenum >
Since tacrolimus metabolism was inhibited by the specific CYP3A inhibitors, troleandomycin and ketoconazole, we concluded that these enzymes are involved in intestinal metabolism of tacrolimus.
Tacrolimus metabolites re‐entered the mucosa chamber (>90%) and passed through the small intestinal preparation into the serosa chamber.
It is concluded that tacrolimus is metabolized in the intestine, that the metabolites are able to re‐enter the gut lumen and also enter into the portal vein and that small intestinal metabolism and transport is at least in part responsible for the low oral bioavailability of tacrolimus
Antiarrhythmic action of rilmenidine on adrenaline‐induced arrhythmia via central imidazoline receptors in halothane‐anaesthetized dogs
Authors: Mammoto Tadanori , Kamibayashi Takahiko , Hayashi Yukio , Yamatodani Atsushi , Takada Koji , Yoshiya Ikuto 
Published: July 2012

To elucidate the role of central imidazoline receptors in the genesis of adrenaline‐induced arrhythmias under halothane anaesthesia, we investigated the effects of rilmenidine, a selective agonist at imidazoline receptors, on this type of arrhythmia in dogs. Rilmenidine (1, 3, 10 μg kg−1, i.v.) did not affect basal haemodynamic parameters (heart rate and blood pressure), but dose‐dependently inhibited adrenaline‐induced arrhythmias under halothane anaesthesia.
Although, rilmenidine has a weak affinity for α2‐adrenoceptors, pretreatment with idazoxan (10 μg kg−1, intracistenally i.c.), an imidazoline receptor antagonist which has also α2‐adrenoceptor blocking potency, blocked the antiarrhythmic effect of rilmenidine (10 μg kg−1, i.v.). In contrast, pretreatment with rauwolscine (20 μg kg−1, i.c.), a classical α2‐adrenoceptor antagonist with little affinity for imidazoline receptors, did not affect the effect of rilmenidine (10 μg kg−1, i.v.). Furthermore, bilateral vagotomy completely blocked the antiarrhythmic action of rilmenidine (10 μg kg−1, i.v.).
It is suggested that the antiarrhythmic action of rilmenidine is due to the activation of central imidazoline receptors and that vagal tone is critical for this action of rilmenidine.
Block of pancreatic ATP‐sensitive K+ channels and insulinotrophic action by the antiarrhythmic agent, cibenzoline
Authors: Ishida‐Takahashi Ayako , Horie Minoru , Tsuura Yoshiyuki , Ishida Hitoshi , Ai Tomohiko , Sasayama Shigetake 
Published: July 2012

We investigated the effect of cibenzoline (a class Ia antiarrhythmic drug) on basal insulin secretory activity of rat pancreatic islets and ATP‐sensitive K+ channels (KATP) in single pancreatic β cells of the same species, using radioimmunoassay and patch clamp techniques.
Micromolar cibenzoline had a dose‐dependent insulinotrophic action with an EC50 of 94.2±46.4 μm;. The compound inhibited the activity of the KATP channel recorded from a single β‐cell in a concentration‐dependent manner. The IC50 was 0.4 μm in the inside‐out mode and 5.2 μm in the cell‐ attached mode, at pH 7.4.
In the cell‐attached mode, alkalinization of extracellular solution increased the inhibitory action of cibenzoline and the IC50 was reduced from 26.8 μm at pH 6.2 to 0.9 μm at pH 8.4. On the other hand, the action of cibenzoline in the excised inside‐out mode was acute in onset with a small IC50, indicating that the drug attains its binding site from the cytoplasmic side of the cell membrane.
In the inside‐out mode, micromolar ADP reactivated the cibenzoline‐blocked KATP channels in a manner similar to that by which ADP restored ATP‐dependent block of the channel.
The binding of [3H]‐glibenclamide to pancreatic islets was inhibited by glibenclamide but not by cibenzoline. In contrast, the [3H]‐cibenzoline binding was displaced by unlabelled cibenzoline but not by glibenclamide. It is concluded that cibenzoline blocks pancreatic KATP channels via a binding site distinct from the sulphonylurea receptor.
Investigation of the involvement of the N‐methyl‐D‐aspartate receptor macrocomplex in the development of spermine‐induced CNS excitation in vivo
Authors: Doyle K.M. , Shaw G.G. 
Published: July 2012

The involvement of the N‐methyl‐D‐asparate (NMDA) receptor macrocomplex in the development of spermine‐induced CNS excitation in vivo was investigated.
Injection of 100 μg of spermine into the left lateral cerebral ventricle of female Laca mice (20–25 g) resulted in the development of two distinct phases of CNS excitatory effects which were quantified by a scoring system.
The first phase effects occurred within minutes of injection and generally lasted for about 1 h. Most mice showed scratching of the upper body, frequent face washing and some mice developed clonic convulsions. By about 2 h after injection, the second phase of effects began to develop in the form of body tremor which worsened with time and culminated in fatal tonic convulsions, generally within 8 h of injection.
Pretreatment of the mice with dizocilpine (0.3 mg kg−1, i.p.) resulted in antagonism of the first phase of spermine‐induced effects, but a higher dose (0.3 mg kg−1, (x2), i.p.) was necessary to inhibit the second phase effects.
Whereas the glutamate antagonist, 3‐((R)‐2‐carboxypiperazin‐4‐yl) propyl‐1‐phosphonic acid (D‐CPP) (10, 20 mg kg−1, i.p.), the glycine antagonist 7‐chlorokynurenate (10, 30, 50 nmol, i.c.v.), or the polyamine antagonist ifenprodil (30, 60 mg kg−1, i.p.) antagonized the first phase of effects produced by spermine, these agents given as monotherapy, were ineffective against the development of the second phase of effects.
Co‐administration of ifenprodil with either D‐CPP or 7‐chlorokynurenate resulted in a dose‐dependent antagonism of the development of the second phase of spermine‐induced effects.
It is concluded that the development of the two temporally distinct phases of spermine‐induced effects may be mediated by pharmacologically distinct mechanisms, although the results suggest that the NMDA receptor macrocomplex may be involved in both phases of effects. Furthermore, a moderate dose of D‐CPP or 7‐chlorokynurenate appears to enhance the inhibitory potential of ifenprodil in vivo.
Effects of ranolazine on L‐type calcium channel currents in guinea‐pig single ventricular myocytes
Authors: Allen T.J.A. , Chapman R.A. 
Published: July 2012

Ranolazine has protective effects against ischaemia as exemplified by a reduction of the associated enzyme release and an attenuation of the fall of ATP and other metabolic changes. It has been suggested that ranolazine may affect GTP‐binding proteins involved in the β‐adrenergic protein kinase A (PKA) cascade by interacting with Gs. Calcium channel currents are stimulated by this cascade but the effect of ranolazine upon them is not known. The whole cell patch clamp technique was used to examine the action of ranolazine on basal calcium channel currents and those stimulated by activation at various steps in the PKA cascade.
Ranolazine had only a small effect on the basal calcium current (100 μm caused 11.3% inhibition), but markedly attenuated the β‐adrenoceptor stimulated current (20 nM isoprenaline increased current by 2.3 fold, 10 μm ranolazine inhibited this increase by 47.6%). When the PKA cascade was activated downstream to the receptor by either G‐protein activation with Gpp[NH]p or adenylate cyclase activation with forskolin, the calcium current showed a sensitivity to ranolazine similar to the basal current. Activation of the PKA cascade via H2 receptors gave rise to currents which showed an intermediate sensitivity to ranolazine. Ranolazine inhibition of ICa persisted during muscarinic attenuation of β‐adrenoceptor activation.
The results indicate that ranolazine, at concentrations which have significantly beneficial effects during ischaemic episodes, only greatly affects whole cell calcium current when facilitated by β‐adrenoceptor or histamine receptor activation. Ranolazine would appear to act at the receptor level, rather than at the GTP‐binding or Gs/adenylate cyclase level. An additional smaller effect is also present, which may be mediated by a direct effect on the channel, or components closely associated with it.
Ability of angiotensin II to modulate striatal dopamine release via the AT1 receptor in vitro and in vivo
Authors: Brown D. Charles , Steward Lucinda J. , Ge Jian , Barnes Nicholas M. 
Published: July 2012

The ability of angiotensin II to modulate dopamine release from rat striatal slices in vitro and in the intact rat striatum in vivo was assessed by the microdialysis technique.
In slices of rat striatum, angiotensin II (0.1‐1.0 μm) induced a concentration‐related increase in endogenous dopamine release which was maximal (approximately 250% above basal levels) within the first 2–4 min of agonist application and subsequently declined to near basal values. The angiotensin II‐induced increase in dopamine release was Ca2+‐dependent and was completely antagonized by the selective AT1 receptor antagonist, losartan (1.0 μm). In contrast, the AT2 receptor antagonist, PD123177 (1.0 μm) failed to modify the angiotensin II‐induced response. Neither antagonist alone modified basal dopamine release from striatal slices.
In freely moving rats, angiotensin II (1.0–10 μm; administered via the microdialysis probe) induced a concentration‐related increase in extracellular levels of dopamine which was maximal (approximately 150% above basal levels) within 20–40 min of agonist application and subsequently declined. The angiotensin II (10 μm)‐induced increase in extracellular levels of dopamine was completely antagonized by the AT1 receptor antagonist, losartan (0.1‐1.0 μm; administered via the microdialysis probe) but not by the AT2 receptor antagonist, PD123177 (1.0 μm; administered via the microdialysis probe). Neither antagonist alone modified basal extracellular levels of dopamine.
Homogenate radioligand binding studies with [125I]‐angiotensin II (0.1 nM) identified relatively low levels of specific binding sites in rat striatal homogenates compared to homogenates of pyriform cortex (51.3±9.2 and 651.3±55.1 fmol g−1 wet weight, respectively, mean ± s.e. mean, n = 3; non‐specific binding defined by unlabelled angiotensin II). The majority of the specific [125I]‐angiotensin II (0.1 nM) binding in the striatal and pyriform cortex homogenates was sensitive to the selective AT1 receptor antagonist, losartan (1.0 μm).
In conclusion, the present study provides direct evidence that angiotensin II acting via the AT1 receptor subtype facilitates the release of dopamine in the rat striatum in vitro and in vivo. This receptor‐mediated response may account for the modulation of dopamine‐mediated behavioural responses by antagonists of the AT1 receptor and inhibitors of angiotensin converting enzyme.
Discrimination by PPADS between endothelial P2Y‐ and P2U‐ purinoceptors in the rat isolated mesenteric arterial bed
Authors: Ralevic Vera , Burnstock Geoffrey 
Published: July 2012

The main aim of this study was to characterize the antagonistic effects of pyridoxalphosphate‐6‐ azophenyl‐2′,4′‐disulphonic acid (PPADS) at coexisting endothelial P2Y‐ and P2U‐purinoceptors. Studies were conducted in Krebs‐perfused mesenteric arterial preparations isolated from the rat, with tone raised by methoxamine (5–50 μm).
Purine and pyrimidine compounds elicited vasodilatation with a rank order of potency of 2‐methylthio ATP (2‐MeSATP) = ADP>ATP = UTP>P1, P3‐diadenosine triphosphate (Ap3A)>P1, P2‐ diadenosine pyrophosphate (Ap2A)>NADP> adenosine. 8‐para‐Sulphophenyltheophylline (8‐PSPT; 3 μm) had no effect on vasodilator responses to 2MeSATP, ADP, ATP, UTP, Ap3A or NADP, but blocked responses to adenosine and the maximal response to Ap2A.
PPADS (3–100 μm) attenuated vasodilator responses to the P2Y‐selective agonists 2MeSATP and ADP, shifting the dose‐response curves to the right. The pA2 values for PPADS at 2MeSATP and ADP were 5.97 ± 0.69 and 5.98 ± 0.86 respectively. In contrast, PPADS had no effect on vasodilator responses mediated by the P2U‐selective agonist, UTP, or on vasodilator responses mediated by ATP.
PPADS (10 μm) was used to characterize responses mediated by the adenine dinucleotides; dose‐response curves for vasodilator responses to Ap3A and NADP, but not those to Ap2A, were shifted to the right by PPADS. The estimated pA2 values for the effect of PPADS on Ap3A and NADP were 6.38 and 6.26 respectively.
Indomethacin (10 μm) had no effect on vasodilator responses to 2MeSATP, ADP, ATP or UTP.
In conclusion, these results show that PPADS is an antagonist at endothelial P2Y‐ but not P2U‐ purinoceptors in rat mesenteric arteries. These receptors cannot be discriminated by inhibition of prostaglandin synthesis; P2Y‐purinoceptors are, however, sensitive to ADP. Selective antagonism by use of PPADS showed that ATP acts at P2U‐ and not P2Y‐purinoceptors. Ap3A and NADP mediate vasodilatation via P2Y‐purinoceptors, whereas vasodilatation to Ap2A is mediated partly via P1 and possibly via P2U‐purinoceptors.
Dissociation of P2 purinoceptor‐mediated increase in intracellular Ca2+ level from myosin light chain phosphorylation and contraction in rat aorta
Authors: Kitajima Satoshi , Harada Ken‐Ichi , Hori Masatoshi , Ozaki Hiroshi , Karaki Hideaki 
Published: July 2012

The effects of P2 agonists, adenosine‐5′‐triphosphate (ATP), α, β‐methylene‐adenosine‐5′‐triphosphate (α, β‐me‐ATP) and adenosine‐5‐O‐(3‐thiotriphosphate) (ATPγS), on the intracellular free Ca2+ level ([Ca2+]i), myosin light chain (MLC) phosphorylation and force of contraction were examined in vascular smooth muscle of rat aorta.
ATP (0.1 μm‐1 mM), α, β‐me‐ATP (0.1–100 μm) and ATPγS (1–100 μm) induced transient increases followed by sustained increase in [Ca2+]i. The effects of these agonists were concentration‐dependent. Compared with the effects of a high concentration of KCl (17.5–72.4 mM), the contractions induced by these P2 purinoceptor agonists were smaller at a given [Ca2+]i.
In the absence of extracellular Ca2+ (with 0.5 mM EGTA), ATPγS (10 μm) induced large transient increase in [Ca2+]i with only small contraction in Ca2+‐free solution. In contrast, α, β‐me‐ATP (10 μm) induced only a very small increase in [Ca2+]i and contraction.
ATP (1 mM), α, β‐me‐ATP (10 μm) and ATPγS (10 μm), added during stimulation with 0.1 μm noradrenaline, induced additional and transient increases in [Ca2+]i which were also not associated with contraction.
High K+ (72.4 mM) increased MLC phosphorylation with a similar time course to that of the increase in [Ca2+]i (peak phosphorylation was 56% when [Ca2+]i increased to 100%). In contrast, the time course of the increase in MLC phosphorylation due to ATP (1 mM) did not coincide with that of the large increases in [Ca2+]i; MLC phosphorylation increased to only 31% when [Ca2+]i increased to 163%. The MLC phosphorylation due to α, β‐me‐ATP (10 μm) and ATPγS (10 μm), measured at peak [Ca2+]i, were only 19% and 14%, respectively, irrespective of a large increase in [Ca2+]i (138% and 188%, respectively).
The absence of a clear relationship between P2‐purinoceptor‐mediated increase in [Ca2+]i (either by Ca2+ influx or Ca2+ release) and MLC phosphorylation or force generation appears to imply that elevation in [Ca2+]i does not contribute to these responses.
Effects of an AT1 receptor antagonist, an ACE inhibitor and a calcium channel antagonist on cardiac gene expressions in hypertensive rats
Authors: Kim Shokei , Ohta Kensuke , Hamaguchi Akinori , Yukimura Tokihito , Miura Katsuyuki , Iwao Hiroshi 
Published: July 2012

This study was undertaken to determine whether the AT1 receptor directly contributes to hypertension‐induced cardiac hypertrophy and gene expressions.
Stroke‐prone spontaneously hypertensive rats (SHRSP) were given orally an AT1 receptor antagonist (losartan, 30 mg kg−1 day−1), an angiotensin converting enzyme inhibitor (enalapril 10 mg kg−1 day−1), a dihydropyridine calcium channel antagonist (amlodipine, 5 mg kg−1 day−1), or vehicle (control), for 8 weeks (from 16 to 24 weeks of age). The effects of each drug were compared on ventricular weight and mRNA levels for myocardial phenotype‐ and fibrosis‐related genes.
Left ventricular hypertrophy of SHRSP was accompanied by the increase in mRNA levels for two foetal phenotypes of contractile proteins (skeletal α‐actin and β‐myosin heavy chain (β‐MHC)), atrial natriuretic polypeptide (ANP), transforming growth factor‐β‐1 (TGF‐β1) and collagen, and a decrease in mRNA levels for an adult phenotype of contractile protein (α‐MHC). Thus, the left ventricle of SHRSP was characterized by myocardial transition from an adult to a foetal phenotype and interstitial fibrosis at the molecular level.
Although losartan, enalapril and amlodipine lowered blood pressure of SHRSP to a comparable degree throughout the treatment, losartan caused regression of left ventricular hypertrophy of SHRSP to a greater extent than amlodipine (P < 0.01).
Losartan significantly decreased mRNA levels for skeletal α‐actin, ANP, TGF‐β1 and collagen types I, III and IV and increased α‐MHC mRNA in the left ventricle of SHRSP. Amlodipine did not alter left ventricular ANP, α‐MHC and collagen types I and IV mRNA levels of SHRSP.
The effects of enalapril on left ventricular hypertrophy and gene expressions of SHRSP were similar to those of losartan, except for the lack of inhibition of collagen type I expression by enalapril.
Unlike the hypertrophied left ventricle, there was no significant difference between losartan and amlodipine in the effects on non‐hypertrophied right ventricular gene expressions of SHRSP.
Our results show that hypertension causes not only left ventricular hypertrophy but also molecular transition of myocardium to a foetal phenotype and interstitial fibrosis‐related molecular changes. These hypertension‐induced left ventricular molecular changes may be at least in part mediated by the direct action of local angiotensin II via the AT1 receptor.
Bosentan‐improved cardiopulmonary vascular performance and increased plasma levels of endothelin‐1 in porcine endotoxin shock
Authors: Weitzberg Eddie , Hemsén Anette , Rudehill Anders , Modin Agnes , Wanecek Michael , Lundberg Jan M. 
Published: July 2012

To evaluate the possible contribution of endothelin‐1 (ET‐1) to the pathophysiology of porcine septic shock, the non‐peptide, mixed ET‐receptor antagonist, bosentan (RO 47–0203) was administered (5 mg kg−1, i.v.) 30 min before infusion of lipopolysaccharide (LPS) (E. coli., serotype 0111:B4) (15 μg kg−1 h−1) and at 3.5 h of endotoxaemia in six anaesthetized and mechanically ventilated pigs. Six other pigs served as controls and received only LPS infusion. Pulmonary and systemic haemodynamics as well as splenic, renal and intestinal blood flows were measured continuously. Release and synthesis of ET‐1 and Big ET‐1 were also measured.
Only three of the six pigs in the control group survived 3 h of LPS infusion while in the bosentan‐treated group all six pigs were alive at that time. A biphasic increase in mean pulmonary arterial pressure (MPAP) and pulmonary vascular resistance (PVR) was seen in control pigs. Pretreatment with bosentan did not influence the first peak but markedly attenuated the second, more prolonged increase in MPAP and PVR. The second dose of bosentan completely restored these parameters to pre‐LPS levels. The LPS‐induced changes in mean arterial blood pressure, heart rate and systemic vascular resistance were similar in both groups, while cardiac output (CO) was significantly higher in the bosentan‐treated group. The second bosentan dose increased CO and splenic and intestinal blood flow without further lowering of blood pressure.
Bosentan caused an increase of the basal arterial plasma levels of ET‐1‐like immunoreactivity (LI), from 16.8 ± 1.3 pM to 49.6 ± 10.0 pM (n = 6, P < 0.01). However, the rate of the increase of ET‐1 levels during the LPS infusion was not affected by bosentan. Repeated administration of bosentan during LPS infusion caused an additional increase of ET‐1‐LI levels. Neither the basal levels of Big ET‐LI nor the LPS induced 8 fold increase in Big ET‐LI were changed by bosentan. The level of preproET‐1 mRNA in the lung was increased about 3 fold after 4.5 h of LPS treatment. This elevation was not influenced by bosentan.
From these studies using bosentan, a non‐peptide, selective and mixed ET‐receptor antagonist, we conclude that during LPS‐induced shock bosentan can abolish the late phase pulmonary hypertension and improve cardiac output as well as increase blood flow to the splenic and intestinal vascular beds without causing a further decrease in mean arterial blood pressure. Further investigations in the clinical setting are needed to evaluate the use of ET‐receptor antagonists, such as bosentan, in treatment of septic shock.