bluuebunny/crossref_metadata_2025_split huggingface dataset:
Sources of Ca2+ in relation to generation of acetylcholine‐induced endothelium‐dependent hyperpolarization in rat mesenteric artery
Authors: Fukao Mitsuhiro , Hattori Yuichi , Kanno Morio , Sakuma Ichiro , Kitabatake Akira 
Published: August 2006

The aim of the present study was to identify the sources of Ca2+ contributing to acetylcholine (ACh)‐induced release of endothelium‐derived hyperpolarizing factor (EDHF) from endothelial cells of rat mesenteric artery and to assess the pathway involved. The changes in membrane potentials of smooth muscles by ACh measured with the microelectrode technique were evaluated as a marker for EDHF release.
ACh elicited membrane hyperpolarization of smooth muscle cells in an endothelium‐dependent manner. The hyperpolarizing response was not affected by treatment with 10 μm indomethacin, 300 μm NG‐nitro‐l‐arginine or 10 μm oxyhaemoglobin, thereby indicating that the hyperpolarization is not mediated by prostanoids or nitric oxide but is presumably by EDHF.
In the presence of extracellular Ca2+, 1 μm ACh generated a hyperpolarization composed of the transient and sustained components. By contrast, in Ca2+‐free medium, ACh produced only transient hyperpolarization.
Pretreatment with 100 nm thapsigargin and 3 μm cyclopiazonic acid, endoplasmic reticulum Ca2+‐ATPase inhibitors, completely abolished ACh‐induced hyperpolarization. Pretreatment with 20 mm caffeine also markedly attenuated ACh‐induced hyperpolarization. However, the overall pattern and peak amplitude of hyperpolarization were unaffected by pretreatment with 1 μm ryanodine.
In the presence of 5 mm Ni2+ or 3 mm Mn2+, the hyperpolarizing response to ACh was transient, and the sustained component of hyperpolarization was not observed. On the other hand, 1 μm nifedipine had no effect on ACh‐induced hyperpolarization.
ACh‐induced hyperpolarization was nearly completely eliminated by 500 nm U‐73122 or 200 μm 2‐nitro‐4‐carboxyphenyl‐N,N‐diphenylcarbamate, inhibitors of phospholipase C, but was unchanged by 500 nm U‐73343, an inactive form of U‐73122. Pretreatment with 20 nm staurosporine, an inhibitor of protein kinase C, did not modify ACh‐induced hyperpolarization.
These results indicate that the ACh‐induced release of EDHF from endothelial cells of rat mesenteric artery is possibly initiated by Ca2+ release from inositol 1,4,5‐trisphosphate (IP3)‐sensitive Ca2+ pool as a consequence of stimulation of phospholipid hydrolysis due to phospholipase C activation, and maintained by Ca2+ influx via a Ni2+‐ and Mn2+‐sensitive pathway distinct from L‐type Ca2+ channels. The Ca2+‐influx mechanism seems to be activated following IP3‐induced depletion of the pool.

British Journal of Pharmacology (1997) 120, 1328–1334; doi:10.1038/sj.bjp.0701027
Direct cardiac and vascular actions of adrenomedullin in conscious sheep
Authors: Parkes David G , May Clive N 
Published: August 2006

Adrenomedullin (ADM) is a recently characterized circulating hormone which affects haemodynamic, renal and pituitary function in mammals. We have shown previously that in sheep, ADM produces vasodilatation together with increases in cardiac output and contractility. However, whether these effects are direct or mediated by autonomic reflexes is unclear. The present study examined the cardiovascular actions of an intravenous infusion of ADM in conscious, chronically instrumented sheep with either sympathetic, parasympathetic or autonomic ganglion blockade, to determine the role of the autonomic nervous system in mediating these cardiovascular changes.
Human ADM (1–52) was infused for 60 min at 2 μg kg−1 h−1 following: (1) saline control, (2) combined α/β‐adrenoceptor (sympathetic) blockade (proporanolol 0.4 mg kg−1 h−1+phentolamine 0.15 mg kg−1 h−1 for 20 h), (3) muscarinic (parasympathetic) blockade (methscopolamine 0.05 mg kg−1 h−1 for 20 h) or (4) ganglion blockade (hexamethonium 3 mg kg−1 h−1 for 4 h). Measurements were made of mean arterial pressure (MAP), heart rate (HR), cardiac output (CO), stroke volume (SV), total peripheral conductance (TPC), maximal aortic flow (Fmax) and maximal rate of change of aortic flow (dF/dt).
ADM reduced MAP by 3±1 mmHg, and increased CO (1.2±0.2 l min−1), HR (14±2 beats min−1), TPC (21±3 ml min−1 mmHg−1), Fmax (2.3±0.8 l min−1) and dF/dt (86±21 l min−1 s−1) in normal sheep. In animals with α/β blockade, similar changes were observed with ADM. However, during muscarinic blockade, the increases in HR (32±4 beats min−1), CO (2.1±0.4 l min−1), TPC (31±4 ml min−1 mmHg−1), Fmax (4.0±0.6 l min−1), and dF/dt (150±12 l min−1 s−1) produced by ADM were enhanced. During ganglion blockade, ADM produced a greater reduction in MAP (−10±2 mmHg) compared to controls (−3±1 mmHg). However, there was no increase in HR. The changes in CO, TPC and contractility were similar to those observed in control animals.
These results suggest that the vasodilator effects of ADM on the periphery and its ability to increase CO and cardiac contractility are not mediated by the autonomic nervous system, but are probably the result of direct actions of ADM on the heart and vasculature.

British Journal of Pharmacology (1997) 120, 1179–1185; doi:10.1038/sj.bjp.0701034
Activation of endothelin ETA receptors masks the constrictor role of endothelin ETB receptors in rat isolated small mesenteric arteries
Authors: Mickley Emma J. , Gray Gillian A. , Webb David J. 
Published: August 2006

Endothelin‐1 (ET‐1) produces constriction of the rat mesenteric vascular bed in vivo via ETA and ETB receptor subtypes. The aim of this study was to investigate the relative roles of these receptor subtypes in rat isolated, endothelium‐denuded, small mesenteric arteries, under pressure, by use of ET‐1; the ETA receptor antagonist, BQ‐123; the ETB receptor selective agonist, sarafotoxin S6c (SRTX S6c); the ETB receptor selective antagonist, BQ‐788; and the ETA/ETB antagonist, TAK‐044.
In 3rd generation mesenteric arteries, ET‐1 (10−1310−7 m) produced concentration‐dependent contractions (pD2 9.86). SRTX S6c (10−1210−7 m) also induced concentration‐dependent contractions in 53% of arteries studied, although the Emax was much less than that obtained with ET‐1 (10.7±2.9% vs 101.9±2.6% of the 60 mm KCl‐induced contraction).
Neither ETB receptor desensitization, by a supra‐maximal concentration of SRTX S6c (10−7 m), nor incubation with BQ‐788 (3×10−8 m), had any significant effect on the ET‐1 concentration‐response curve, although both treatments tended to enhance rather than inhibit responses to ET‐1.
In the presence of BQ‐123 (10−6 m), responses to low concentrations of ET‐1 (up to 10−10 m) were unaffected but responses to concentrations of ET‐1 above 10−10 m were significantly inhibited.
SRTX S6c desensitization followed by incubation with BQ‐123 (10−6 m) or co‐incubation with BQ‐788 (3×10−8 m) and BQ‐123 caused inhibition of responses to all concentrations of ET‐1, resulting in a rightward shift of the ET‐1 concentration‐response curve. The same effect was obtained by incubation with TAK‐044 (10−8 m and 3×10−7 m).
Thus, responses of rat small mesenteric arteries to ET‐1 are mediated by both ETA and ETB receptors. The relative role of ETB receptors is greater than that predicted by the small responses to SRTX S6c or by resistance of ET‐1‐induced contraction to ETB receptor desensitization or BQ‐788. The effect of ETB receptor desensitization or blockade is only revealed in the presence of ETA receptor blockade, suggesting the presence of a ‘crosstalk’ mechanism between the receptors. These results support the concept that dual receptor antagonists, like TAK‐044, may be required to inhibit completely constrictor responses to ET‐1.

British Journal of Pharmacology (1997) 120, 1376–1382; doi:10.1038/sj.bjp.0701036
Sites of action of IL‐1 in the development of fever and cytokine responses to tissue inflammation in the rat
Authors: Miller Andrew J. , Hopkins Stephen J. , Luheshi Giamal N. 
Published: August 2006

The objective of the present study was to determine the sites of action of the cytokine, interleukin‐1 (IL‐1), in the febrile response to local inflammation in the rat, by comparing the importance of IL‐1 in the local tissues, the circulation and the brain. This was achieved by injecting lipopolysaccharide (LPS, 100 μg kg−1) into a subcutaneous air pouch and testing the effects of blocking IL‐1 action with the human recombinant interleukin‐1 receptor antagonist (IL‐1ra) injected either into the air pouch, intraperitoneally (1 mg kg−1, 0+1 h, i.p.), or intracerebroventricularly (200 μg/rat, 0+1 h, i.c.v.).
To investigate the effect of IL‐1ra on fever and the induction of local and circulating cytokines (IL‐1 and IL‐6), separate experiments were performed in which groups of animals were killed 1.5, 3 or 5 h after LPS injection. Plasma and pouch fluid samples were collected for bioassay of IL‐1 and IL‐6.
Injection of LPS into the air pouch significantly increased (1.5°C) body temperature, local (air pouch) concentrations of bioactive IL‐1 and IL‐6, and circulating bioactive IL‐6, compared to saline‐treated controls.
Injection of IL‐1ra into the pouch significantly attenuated LPS fever (P<0.001). This decrease in body temperature was associated with significant inhibition of local IL‐1 bioactivity 1.5 (96%), 3 (84%) and 5 h (72%), and in bioactive IL‐6 in pouch lavage fluid 1.5 (45%) and 5 h (35%), after LPS injection. The concentration of bioactive IL‐6 in the plasma was significantly reduced (39%) at 3 h, when temperature was approaching the maximal value.
Both systemic (i.p.) and central (i.c.v.) administration of IL‐1ra significantly attentuated LPS fever (P<0.05). However, it had no effect on either local concentrations of bioactive IL‐1 or IL‐6, or circulating IL‐6, at any of the sample points.
These data suggest that IL‐1 is released locally, at the site of tissue inflammation and that it is an important mediator of the febrile response to local inflammation. The results also indicate that IL‐1 produced locally may contribute to the production of IL‐6 which is released into the circulation, and that IL‐1 has important actions in the generation of fever at other sites, including the brain.

British Journal of Pharmacology (1997) 120, 1274–1279; doi:10.1038/sj.bjp.0701049
Contribution of α‐adrenoceptors to depolarization and contraction evoked by continuous asynchronous sympathetic nerve activity in rat tail artery
Authors: Brock J. A. , Mclachlan E. M. , Rayner S. E. 
Published: August 2006

The effects of continuous but asynchronous nerve activity induced by ciguatoxin (CTX‐1) on the membrane potential and contraction of smooth muscle cells have been investigated in rat proximal tail arteries isolated in vitro. These effects have been compared with those produced by the continuous application of phenylephrine (PE).
CTX‐1 (0.4 nm) and PE (10 μm) produced a maintained depolarization of the arterial smooth muscle that was almost completely blocked by α‐adrenoceptor blockade. In both cases, the depolarization was more sensitive to the selective α2‐adrenoceptor antagonist, idazoxan (0.1 μm), than to the selective α1‐adrenoceptor antagonist, prazosin (0.01 μm).
In contrast, the maintained contraction of the tail artery induced by CTX‐1 (0.2 nm) and PE (2 and 10 μm) was more sensitive to prazosin (0.01) μm, than to idazoxan (0.01 μm). In combination, these antagonists almost completely inhibited contraction to both agents.
Application of the calcium channel antagonist, nifedipine (1 μm), had no effect on the depolarization induced by either CTX‐1 or PE but maximally reduced the force of the maintained contraction to both agents by about 50%.
We conclude that the constriction of the tail artery induced by CTX‐1, which mimics the natural discharge of postganglionic perivascular axons, is due almost entirely to α‐adrenoceptor activation. The results indicate that neuronally released noradrenaline activates more than one α‐adrenoceptor subtype. The depolarization is dependent primarily on α2‐adrenoceptor activation whereas the contraction is dependent primarily on α1‐adrenoceptor activation. The links between α‐adrenoceptor activation and the voltage‐dependent and voltage‐independent mechanisms that deliver Ca2+ to the contractile apparatus appear to be complex.

British Journal of Pharmacology (1997) 120, 1513–1521; doi:10.1038/sj.bjp.0701055
Sequential development of angiotensin receptors and angiotensin I converting enzyme during angiogenesis in the rat subcutaneous sponge granuloma
Authors: Walsh David A. , Hu De‐En , Wharton John , Catravas John D. , Blake David R. , Fan Tai‐Ping D. 
Published: August 2006

The vasoconstrictor peptide antiotensin II (AII) can stimulate angiogenesis, an important process in wound healing, tumour growth and chronic inflammation. To elucidate mechanisms underlying AII‐enhanced angiogenesis, we have studied a subcutaneous sponge granuloma model in the rat by use of 133Xe clearance, morphometry and quantitative in vitro autoradiography.
When injected directly into the sponge, AII (1 nmol day−1) increased 133Xe clearance from, and fibrovascular growth in sponge granulomas, indicating enhanced angiogenesis 6 to 12 days after implantation. This AII‐enhanced angiogenesis was inhibited by daily doses (100 nmol/sponge) of the specific but subtype non‐selective AII receptor antagonist (Sar1, Ile8)AII, and by the selective non‐peptide AT1 receptor antagonists losartan and DuP 532. In contrast, AII‐enhanced neovascularization was not inhibited by the AT2 receptor antagonist PD123319, nor was it mimicked by the AT2 receptor agonist CGP42112A (each at 100 nmol/sponge day−1).
AI (1 nmol/sponge day−1), the angiotensin converting enzyme (ACE) inhibitors captopril (up to 100 μg/sponge day−1) and lisinopril (40 μg/sponge day−1), or AII receptor antagonists did not affect angiogenesis in the absence of exogenous AII.
[125I]‐(Sar1, Ile8)AII binding sites with characteristics of AT1 receptors were localized to microvessels and to non‐vascular cells within the sponge stroma from 4 days after implantation, and were at higher density than in skin throughout the study.
[125I]‐(Sar1, Ile8)AII binding sites with characteristics of AT2 receptors were localized to non‐vascular stromal cells, were of lower density and appeared later than did AT1 sites.
The ACE inhibitor [125I]‐351A bound to sites with characteristics of ACE, 14 days after sponge implantation. [125I]‐351A bound less densely to sponge stroma than to skin.
We propose that AII can stimulate angiogenesis, acting via AT1 receptors within the sponge granuloma. AT1 and AT2 receptors and ACE develop sequentially during microvascular maturation, and the role of the endogenous angiotensin system in angiogenesis will depend on the balanced local expression of its various components. Pharmacological modulation of this balance may provide novel therapeutic approaches in angiogenesis‐dependent diseases.

British Journal of Pharmacology (1997) 120, 1302–1311; doi:10.1038/sj.bjp.0701062
The involvement of pertussis toxin‐sensitive G proteins in the post receptor mechanism of central I1‐imidazoline receptors
Authors: Takada Koji , Hayashi Yukio , Kamibayashi Takahiko , Mammoto Tadanori , Yamatodani Atsushi , Kitamura Seiji , Yoshiya Ikuto 
Published: August 2006

To elucidate the possible involvement of pertussis toxin (PTX)‐sensitive G proteins in the post receptor mechanism of α2‐adrenoceptors and imidazoline receptors, we examined the effect of pretreatment of the central nervous system with PTX on the antidysrhythmic effect of dexmedetomidine, a selective α2‐adrenoceptor agonist, and rilmenidine, a selective I1‐imidazoline receptor agonist on halothane‐adrenaline dysrhythmias in rats.
Dexmedetomidine (0, 1.0, 2.0, 5.0 μg kg−1 min−1, i.v.) and rilmenidine (0, 1.0, 3.0, 10, 20 μg kg−1, i.v.) prevented the genesis of halothane‐adrenaline dysrhythmias in a dose‐dependent fashion. Both idazoxan (10, 20 μg kg−1, intracerebroventricularly (i.c.v.)), an α2‐adrenoceptor antagonist with high affinity for imidazoline receptors, and rauwolscine, (40 μg kg−1, i.c.v.), an α2‐adrenoceptor antagonist with low affinity for imidazoline receptors inhibited the action of dexmedetomidine (5.0 μg kg−1 min−1, i.v.), but the inhibitory potency of idazoxan was much greater than that of rauwolscine. While the pretreatment with PTX (0.1, 0.5, 1.0 μg kg−1, i.c.v.) did not change the dysrhythmogenecity of adrenaline, this treatment completely blocked the antidysrhythmic property of rilmenidine (20 μg kg−1, i.v.) as well as dexmedetomidine (5.0 μg kg−1 min−1, i.v.).
It is suggested that central I1‐imidazoline receptors as well as α2‐adrenoceptors may be functionally coupled to PTX‐sensitive G proteins.

British Journal of Pharmacology (1997) 120, 1575–1581; doi:10.1038/sj.bjp.0701090
Pharmacological evidence that the activation of the Na+‐Ca2+ exchanger protects C6 glioma cells during chemical hypoxia
Authors: Amoroso Salvatore , De Maio Matteo , Russo Giovanni M , Catalano Annalisa , Bassi Antonella , Montagnani Stefania , Di Renzo Gianfranco , Annunziato Lucio 
Published: August 2006

In C6 glioma cells exposed to chemical hypoxia a massive release of lactate dehydrogenase (LDH) occurred at 3 and 6 h, coupled with an increased number of propidium‐iodide positive dead cells.
Extracellular Na+ removal, which activates the Na+‐Ca2+ exchanger as a Na+ efflux pathway and prevents Na+ entrance, significantly reduced LDH release and the number of propidium iodide positive C6 cells.
During chemical hypoxia, in the presence of extracellular Na+ ions, a progressive increase of [Ca2+]i occurred; in the absence of extracellular Na+ ions [Ca2+]i was enhanced to a greater extent.
The blockade of the Na+‐Ca2+ exchanger by the amiloride derivative 5‐(N‐4‐chlorobenzyl)‐2′,4′‐dimethylbenzamil (CB‐DMB), lanthanum (La3+) and the Ca2+ chelator EGTA, completely reverted the protective effect exerted by the removal of Na+ ions on C6 glioma cells exposed to chemical hypoxia.
The inhibition of the Na+‐Ca2+ antiporter enhanced chemical hypoxia‐induced LDH release when C6 glioma cells were incubated in the presence of physiological concentrations of extracellular Na+ ions (145 mM), suggesting that the blockade of the Na+‐Ca2+ antiporter during chemical hypoxia can lead to increased cell damage.
Collectively, these results suggest that activation of the Na+‐Ca2+ exchanger protects C6 glioma cells exposed to chemical hypoxia, whereas its pharmacological blockade can exacerbate cellular injury.

British Journal of Pharmacology (1997) 121, 303–309; doi:10.1038/sj.bjp.0701092
Mechanism of enhanced vasoconstrictor hormone action in vascular smooth muscle cells by cyclosporin A
Authors: Lo Russo Alexandre , Passaquin Anne‐Catherine , Rüegg Urs T 
Published: August 2006

The use of the immunosuppressive drug cyclosporin A (CsA) is limited by two major side effects, nephrotoxicity and hypertension, which are caused by drug‐induced local vasoconstriction. We have recently shown that CsA potentiates the contraction of isolated resistance arteries to vasoconstrictor hormones and increases the calcium response to these agents in vascular smooth muscle cells (VSMC). The goal of the present study was to investigate further the molecular mechanism(s) involved in these effects.
Stimulation of VSMC with [Arg]8vasopressin (AVP) induced a concentration‐dependent increase in total inositol phosphates (InsP) and cellular calcium response (as measured by 45Ca2+ efflux). Preincubation of VSMC with CsA increased both InsP formation and 45Ca2+ efflux.
The potentiating effect of CsA on AVP‐elicited InsP formation and 45Ca2+ efflux was inhibited by co‐incubation with the protein synthesis inhibitors actinomycin D and cycloheximide, indicating that CsA acted on gene expression.
Binding experiments with [3H]‐AVP on VSMC showed that CsA increased the number of AVP receptors by about two fold without affecting receptor affinity. Actinomycin D completely blocked this increase.
These results demonstrate for the first time that incubation of VSMC with CsA increases the expression of AVP receptors, resulting in a potentiation of InsP formation and calcium response upon stimulation with AVP. This effect of CsA is likely to occur with other vasoconstrictor hormone receptors as well and could be a key mechanism in the induction of vasoconstriction, and subsequent drug‐induced nephrotoxicity and hypertension.

British Journal of Pharmacology (1997) 121, 248–252; doi:10.1038/sj.bjp.0701102
Selective induction of cyclo‐oxygenase‐2 activity in the permanent human endothelial cell line HUV‐EC‐C: biochemical and pharmacological characterization
Authors: Miralpeix Montserrat , Camacho Mercedes , López‐Belmonte Jesús , Canalías Francesca , Beleta Jordi , M Palacios José , Vila Luis 
Published: August 2006

Cyclo‐oxygenase (COX), the enzyme responsible for the conversion of arachidonic acid (AA) to prostaglandin H2 (PGH2), exists in two forms, termed COX‐1 and COX‐2 which are encoded by different genes. COX‐1 is expressed constitutively and is known to be the site of action of aspirin and other non‐steroidal anti‐inflammatory drugs. COX‐2 may be induced by a series of pro‐inflammatory stimuli and its role in the development of inflammation has been claimed.
Endothelial cells are an important physiological source of prostanoids and the selective induction of COX‐2 activity has been described for finite cultures of endothelial cells, but not for permanent endothelial cell lines.
The HUV‐EC‐C line is a permanent endothelial cell line of human origin. We have determined the COX activity of these cells under basal conditions and after its exposure to two different stimuli, phorbol 12‐myristate 13‐acetate (PMA) and interleukin‐1β (IL‐1β).
Both PMA and IL‐1β produced dose‐ and time‐dependent increases of the synthesis of the COX‐derived eicosanoids. These increases were maximal after the treatment with 10 nM PMA for 6 to 9 h. Under these conditions, the main eicosanoid produced by the cells was PGE2.
The increase of COX activity by PMA or IL‐1β correlated with an increase of the enzyme's apparent Vmax, whilst the affinity for the substrate, measured as apparent Km, remained unaffected.
Treatment of the cells with PMA induced a time‐dependent increase in the expression of both COX‐1 and COX‐2 mRNAs. Nevertheless, this increase was reflected only as an increase of the COX‐2 isoenzyme at the protein level.
The enzymatic activity of the PMA‐induced COX was measured in the presence of a panel of enzyme inhibitors, and the IC50 values obtained were compared with those obtained for the inhibition of human platelet COX activity, a COX‐1 selective assay. Classical non‐steroidal anti‐inflammatory drugs (NSAIDs) inhibited both enzymes with varying potencies but only the three compounds previously shown to be selective COX‐2 inhibitors (SC‐58125, NS‐398 and nimesulide) showed higher potency towards the COX of PMA‐treated HUV‐EC‐C.
Overall, it appears that the stimulation of the HUV‐EC‐C line with PMA selectively induces the COX‐2 isoenzyme. This appears to be a suitable model for the study of the physiology and pharmacology of this important isoenzyme, with a permanent endothelial cell line of human origin.

British Journal of Pharmacology (1997) 121, 171–180; doi:10.1038/sj.bjp.0701112