bluuebunny/crossref_metadata_2025_split huggingface dataset:
Structural factors that determine the ability of adenosine and related compounds to activate the cardiac ryanodine receptor
Authors: Chan Wei Mun , Welch William , Sitsapesan Rebecca 
Published: January 2005

The effects of adenosine and adenine on the gating of native sheep cardiac ryanodine receptor (RyR) channels were investigated. By examining the mechanisms underlying channel activation and by using comparative molecular field analysis (CoMFA) we have investigated the structural features of adenine‐based ligands involved in channel activation.
In the presence of 10 μM cytosolic Ca2+, adenosine and adenine both activate the channel but only to a level approximately 10 and 20% respectively of that of ATP indicating that both are partial agonists of low efficacy.
Adenosine was able to antagonize the ATP‐induced increase in open probability (Po) as expected for a partial agonist of low efficacy at the ATP sites on the cardiac RyR.
GTP (100 μM–10 mM) had no effect on channel gating indicating that the adenine ring structure is important for agonist activity at the ATP‐sites on RyR.
CoMFA revealed an extremely strong correlation between the structural features of the five ATP analogues and the ability to increase (Po). Our model indicates that the high efficacy of ATP results primarily from the large electrostatic field established by the ionized phosphate groups. Reducing the number of phosphate groups lowers the strength of this field, leading to ligands with lower efficacy. In addition, steric interactions between the α‐phosphate and ribose moieties and the RyR are correlated with low Po.

British Journal of Pharmacology (2000) 130, 1618–1626; doi:10.1038/sj.bjp.0703459
Pharmacological characterization of metabotropic glutamate receptor‐mediated high‐affinity GTPase activity in rat cerebral cortical membranes
Authors: Nishi Nobuyuki , Odagaki Yuji , Koyama Tsukasa 
Published: January 2005

Activation of heterotrimeric guanine nucleotide‐binding regulatory proteins (G‐proteins) functionally coupled to metabotropic glutamate receptors (mGluRs) was assessed by agonist‐induced high‐affinity GTPase (EC3.6.1.‐) activity in rat cerebral cortical membranes.
L‐Glutamate (1 mM) stimulated high‐affinity GTPase activity to the same extent throughout the incubation period up to 20 min, in a Mg2+‐dependent manner. The addition of 1 mM L‐glutamate augmented Vmax of the enzyme activity (1670 to 3850 pmol mg−1 protein 15 min−1) with slight increase in KM value (0.26 to 0.63 μM).
The high‐affinity GTPase activity was stimulated by the following compounds with a rank order of potency of (2S,2′R,3′R)‐2‐(2′,3′‐dicarboxycyclopropyl) glycine (DCG‐IV) >  (2S,1′S,2′S)‐2‐(carboxycyclopyropyl)glycine (L‐CCG‐I) > L‐glutamate ≥ 2R,4R‐4‐aminopyrrolidine‐2,4‐dicarboxylate [(2R,4R)‐APDC] > 1S,3R‐1‐aminocyclopentane‐1,3‐dicarboxylate [(1S,3R)‐ACPD] > (S)‐4‐carboxy‐3‐hydroxyphenylglycine [(S)‐4C3HPG] > (S)‐3‐carboxy‐4‐hydroxyphenylglycine [(S)‐3C4HPG] > ibotenate, but not by L‐(+)‐2‐amino‐4‐phosphonobutyrate (L‐AP4), (RS)‐3,5‐dihydroxyphenylglycine [(RS)‐3,5‐DHPG], quisqualate, or L‐serine‐O‐phosphate (L‐SOP), indicative of involvement of group II mGluRs, in particular mGluR2.
(2S)‐α‐Ethylglutamate (EGLU), a presumably selective antagonist against group II mGluRs, inhibited DCG‐IV‐stimulated high‐affinity GTPase activity in a competitive manner with an apparent KB of 220 μM.
L‐Glutamate‐stimulated activity was eliminated by pretreatment of the membranes with sulfhydryl alkylating agent N‐ethylmaleimide (NEM) at 30–50 μM, indicating that G‐proteins of the Gi family are involved.
These results indicate that mGluR agonist‐induced high‐affinity GTPase activity in rat cerebral cortical membranes may be used to detect the functional interaction between group II mGluRs, in particular mGluR2, and NEM‐sensitive Gi proteins.

British Journal of Pharmacology (2000) 130, 1664–1670; doi:10.1038/sj.bjp.0703464
Cytochrome P450 mono‐oxygenase gene expression and protein activity in cultures of adult cardiomyocytes of the rat
Authors: Thum Thomas , Borlak Jürgen 
Published: January 2005

There are a substantial number of drugs acting either directly or indirectly on the heart, but surprisingly, little is known about the metabolic capacity of heart muscle cells.
We therefore investigated the gene expression and protein activity of cytochrome P450 isozymes in cultures of adult cardiomyocytes of the rat.
Semi‐quantitative CYP gene expression pattern suggests CYP1A1 and CYP2B1/2 to be key players in cardiomyocytes and upon treatment with Aroclor 1254 approximate 4 fold inductions could be observed for both gene families, when compared with appropriate controls.
The mRNA expression of most genes was sustained for prolonged periods of time, e.g. up to 120 h in culture and in the case of the CYP3A1 gene an approximate 10 fold induction was observed at the higher Aroclor 1254 dose level (10 μM) in 24 h old cultures.
The constitutively expressed genes, e.g. CYP2C11 and CYP2E1 are expressed throughout the entire culture period (5 days) and did not respond to Aroclor 1254 treatment.
CYP4A1 was mainly expressed in freshly isolated cardiomyocytes of control animals and its expression declined rapidly in culture.
There was good agreement between gene expression and translated protein activity using 7‐ethoxyresorufin and testosterone as substrates.
The data reported herein should foster the routine use of freshly isolated and cultivated cardiomyocytes for drug profiling and toxicity studies.

British Journal of Pharmacology (2000) 130, 1745–1752; doi:10.1038/sj.bjp.0703465
LU135252, an endothelinA receptor antagonist did not prevent pulmonary vascular remodelling or lung fibrosis in a rat model of myocardial infarction
Authors: Nguyen Quang Trinh , Colombo Federico , Rouleau Jean L , Dupuis Jocelyn , Calderone Angelino 
Published: January 2005

The early intervention with endothelinA (ETA) receptor antagonists following coronary artery ligation has been shown to reduce the development of pulmonary hypertension, despite a lack of improvement in left ventricular function.
The present study examined the contribution of pulmonary vascular remodelling and the progression of lung fibrosis in the development of pulmonary hypertension and the subsequent role of endothelin‐1 in these processes in a rat model of myocardial infarction (MI).
The administration of 60 mg kg−1 per day of the specific ETA receptor antagonist LU135253 ((+)‐(S)‐2‐(4,6‐dimethoxy‐pyrimidin‐2‐yloxy)‐3‐methoxy‐3,3‐diphenyl‐propionic acid) 24 h following coronary artery ligation, failed to improve left ventricular contractile indices, but reduced the extent of pulmonary hypertension, as reflected by the significant decrease in right ventricular systolic pressure.
The medial wall thickness of small pulmonary arteries (50–200 μm) was significantly increased 4 weeks following MI, albeit LU135253 treatment did not ameliorate this pattern of vascular remodelling.
The steady‐state mRNA levels of collagen, fibronectin, transforming growth factor‐β1, and ‐β3 were significantly increased in the lungs of MI rats. The treatment with LU135252 did not alter this pattern of gene expression.
Thus, these data demonstrate pulmonary vascular remodelling and the increased expression of extracellular matrix proteins represent underlying mechanisms implicated in the development of pulmonary hypertension in the MI rat.
Despite the amelioration of the pulmonary hypertensive state, ETA receptor blockade was insufficient to reverse pulmonary vascular remodelling, or the development of lung fibrosis in the MI rat.

British Journal of Pharmacology (2000) 130, 1525–1530; doi:10.1038/sj.bjp.0703466
Cytotoxicity associated with induction of nitric oxide synthase in rat duodenal epithelial cells in vivo by lipopolysaccharide of Helicobacter pylori: inhibition by superoxide dismutase
Authors: Lamarque Dominique , Moran Anthony P , Szepes Zoltan , Delchier Jean‐Charles , Whittle Brendan J R 
Published: January 2005

The products released by Helicobacter pylori (H. pylori) in the gastric antral and duodenal mucosa may be involved in mucosal ulceration by stimulating the local formation of cytotoxic factors such as nitric oxide (NO), superoxide or peroxynitrite.
The present study investigates the ability of purified H. pylori lipopolysaccharide (LPS) to induce nitric oxide synthase (iNOS) in rat duodenal epithelial cells following in vivo challenge and its interaction with superoxide in promoting cellular damage and apoptosis.
H. pylori LPS (0.75–3 mg kg−1 i.v. or 3–12 mg kg−1 p.o.) induced a dose–dependent expression of iNOS activity after 5 h in the duodenal epithelial cells, determined by [14C] arginine conversion to citrulline.
The epithelial cell viability, as assessed by Trypan Blue exclusion and MTT conversion, was reduced 5 h after challenge with H. pylori LPS, while the incidence of apoptosis was increased.
The iNOS activity and reduction in cell viability following H. pylori LPS challenge i.v. was inhibited by the selective iNOS inhibitor, 1400 W (0.2–5 mg kg−1 i.v.).
Concurrent administration of superoxide dismutase conjugated with polyethylene glycol (250–500 i.u. kg−1, i.v.), which did not modify the cellular iNOS activity, reduced the epithelial cell damage provoked by i.v. H. pylori LPS, and abolished the increased incidence of apoptosis.
These results suggest that expression of iNOS following challenge with H. pylori LPS provokes duodenal epithelial cell injury and apoptosis by a process involving superoxide, implicating peroxynitrite involvement. These events may contribute to the pathogenic mechanisms of H. pylori in promoting peptic ulcer disease.

British Journal of Pharmacology (2000) 130, 1531–1538; doi:10.1038/sj.bjp.0703468
Ketamine potentiates cerebrocortical damage induced by the common anaesthetic agent nitrous oxide in adult rats
Authors: Jevtovic‐Todorovic Vesna , Benshoff Nicholas , Olney John W 
Published: January 2005

For general anaesthesia, patients usually receive a combination of drugs, all of which are classified as γ‐amino‐butyric acid (GABA) agonists, with two notable exceptions – ketamine and nitrous oxide (laughing gas, N2O) – which are antagonists of N‐methyl‐D‐aspartate (NMDA) glutamate receptors. At clinically relevant doses both ketamine and N2O, like other NMDA antagonists, have the potential to induce psychotomimetic reactions in humans and to cause pathomorphological changes in cerebrocortical neurons in rat brain. Because drug combinations used in clinical anaesthesia sometimes include both ketamine and N2O, we undertook experiments to evaluate whether augmented neurotoxicity results from their combined use.
Ketamine and N2O were administered alone or in combination by various dosing regimens to adult female rats for a duration of 3 h and the severity of cerebrocortical neurotoxic changes was quantified histologically. Because GABA agonists are known to protect against the psychotomimetic and neurotoxic effects of NMDA antagonists, we also evaluated whether the combined neurotoxicity of ketamine+N2O can be prevented by certain commonly used GABA agonists.
When ketamine and N2O were used in combination the neurotoxic reaction was enhanced to a degree much greater than can be explained by simple additivity. The apparent synergistic interaction was particularly striking when low doses of the agents were combined, the degree of toxic synergism at higher doses being masked by a ceiling effect. GABA agonists protected against ketamine/N2O neurotoxicity.
It is recommended that this information be taken into consideration in the selection of drugs to be used in multi‐agent protocols for general anaesthesia.

British Journal of Pharmacology (2000) 130, 1692–1698; doi:10.1038/sj.bjp.0703479
Cholera toxin treatment of vascular smooth muscle cells decreases smooth muscle α‐actin content and abolishes the platelet‐derived growth factor‐BB‐stimulated DNA synthesis
Authors: Sachinidis Agapios , Seul Claudia , Gouni‐Berthold Ioanna , Seewald Stefan , Ko Yon , Vetter Hans , Fingerle Jürgen , Hoppe Jürgen 
Published: January 2005

The second messenger cyclic AMP regulates diverse biological processes such as cell morphology and cell growth. We examined the role of the second messenger cyclic AMP on rat aortic vascular smooth muscle cell (VSMC) morphology and the intracellular transduction pathway mediated by platelet‐derived growth factor β‐receptor (PDGF‐Rβ).
The effect of PDGF‐BB on VSMCs growth was assessed by [3H]‐thymidine incorporation. Tyrosine phosphorylation of PDGF‐Rβ, PLC‐γ1, ERK1 and ERK2, p125FAK and paxillin as well as Sm α‐actin was examined by the chemiluminescence Western blotting method. Actin mRNA level was quantitated by Northern blotting. Visualization of Sm α‐actin filaments, paxillin and PDGF‐Rβ was performed by immunfluorescence microscopy.
Cholera toxin (CTX; 10 nM) treatment lead to a large and sustained increase in the cyclic AMP concentration after 2 h which correlated with change of VSMC morphology including complete disruption of the Sm α‐actin filament array and loss of focal adhesions. Treatment of VSMCs with CTX did not influence tyrosine phosphorylation of p125FAK and paxillin but decreased the content of a Sm α‐actin protein. Maximal decrease of 70% was observed after 24 h of treatment. CTX also caused a 90% decrease of the actin mRNA level. CTX treatment completely abolished PDGF‐BB stimulated DNA‐synthesis although PDGF‐Rβ level and subcellular distribution and translocation was not altered. Furthermore CTX attenuated the PDGF‐BB‐induced tyrosine phosphorylation of the PDGF‐Rβ, PI 3′‐K, PLC‐γ1 and ERK1/2 indicating an action of cyclic AMP on PDGF‐β receptor.
We conclude that although cyclic AMP attenuates the PDGF‐Rβ mediated intracellular transduction pathway, an intact actin filament may be required for the PDGF‐BB‐induced DNA synthesis in VSMCs.

British Journal of Pharmacology (2000) 130, 1561–1570; doi:10.1038/sj.bjp.0703480
Evidence that adenosine 5′‐triphosphate is the third inhibitory non‐adrenergic non‐cholinergic neurotransmitter in the rat gastric fundus
Authors: Jenkinson Karl M , Reid Julianne J 
Published: January 2005

In the rat gastric fundus, non‐adrenergic, non‐cholinergic (NANC) relaxations are mediated by nitric oxide (NO), vasoactive intestinal polypeptide (VIP), and a third, as yet unidentified, neurotransmitter.
The possible involvement of adenosine 5′‐triphosphate (ATP) in the NANC relaxations was examined using pyridoxalphosphate‐6‐azophenyl‐2′,5′‐disulphonic acid (PPADS), apamin and desensitization to α,β‐methylene ATP. NANC responses were studied in the absence and presence of NG‐nitro‐L‐arginine methyl ester (NAME; 100 μM) and α‐chymotrypsin (1 u ml−1), to inhibit responses to NO and VIP, respectively.
PPADS (100 μM), apamin (1 μM) and desensitization to α,β‐methylene ATP (10 μM, three additions) all significantly (P<0.05) reduced NANC relaxations to electrical field stimulation (0.5–4 Hz, 30 s trains) in longitudinal strips of rat gastric fundus and almost abolished the residual relaxation remaining in the presence of NAME and α‐chymotrypsin.
PPADS had no effect on responses to the NO‐donor, sodium nitroprusside (SNP), or VIP. Apamin slightly reduced relaxations to SNP, but did not affect those to VIP, whereas desensitization to α,β‐methylene ATP markedly reduced responses to both SNP and VIP.
The effects of PPADS and apamin in this study provide strong evidence that the third inhibitory NANC neurotransmitter in the rat gastric fundus is ATP.

British Journal of Pharmacology (2000) 130, 1627–1631; doi:10.1038/sj.bjp.0703481
The P2‐purinoceptor antagonist suramin is a competitive antagonist at vasoactive intestinal peptide receptors in the rat gastric fundus
Authors: Jenkinson Karl M , Reid Julianne J 
Published: January 2005

The P2‐purinoceptor antagonist, suramin, was used to investigate the possible involvement of adenosine 5′‐triphosphate (ATP) in the inhibitory non‐adrenergic non‐cholinergic (NANC) innervation of the rat gastric fundus.
ATP (1–30 μM) produced biphasic responses consisting of concentration‐dependent relaxations followed by concentration‐dependent contractions. Suramin (200 μM) significantly reduced relaxations and abolished contractions to ATP.
Under NANC conditions, electrical field stimulation (EFS) induced frequency‐dependent relaxations. Suramin (200 μM) and the peptidase α‐chymotrypsin (1 u ml−1) had the same effects on EFS‐induced relaxations: their duration was reduced, but their magnitude was unaffected.
Cumulative relaxations to vasoactive intestinal peptide (VIP; 0.1–100 nM), and to the VIP analogue pituitary adenylate cyclase activating peptide 1–27 (PACAP; 0.2–100 nM), were almost completely abolished by α‐chymotrypsin (1 u ml−1), and were inhibited by suramin (3–200 μM) in an apparently competitive manner. Schild plot analysis indicated that suramin had pA2 values of 5.1±0.2 (Hill slope=0.9±0.2) and 5.6±0.1 (Hill slope=1.0±0.1), against VIP and PACAP, respectively.
Concentration‐dependent relaxations to nitric oxide (1–30 μM) and cumulative relaxations to isoprenaline (0.1–300 nM) were not affected by suramin (200 μM).
No conclusions can be made regarding the possible involvement of ATP in EFS‐induced NANC relaxations. The results suggest that suramin acts as a competitive antagonist at VIP receptors in the rat gastric fundus.

British Journal of Pharmacology (2000) 130, 1632–1638; doi:10.1038/sj.bjp.0703482
Effects of a selective neuropeptide Y Y1 receptor antagonist BIBP 3226 on double peaked vasoconstrictor responses to periarterial nerve stimulation in canine splenic arteries
Authors: Yang Xiao‐Ping , Chiba Shigetoshi 
Published: January 2005

The periarterial electrical nerve stimulation (30 s trains of pulses at a frequency of 1, 4 or 10 Hz) induced a double peaked vasoconstriction consisting of an initial transient constriction (first peak) followed by a prolonged response (second peak) in the isolated, perfused canine splenic artery.
At low frequencies (1 and 4 Hz), a neuropeptide Y (NPY) Y1 receptor antagonist BIBP 3226 (0.1–1 μM) produced a dose‐dependent inhibitory effect on the second peak, but did not modify the first peak. At a high frequency (10 Hz), 1 μM BIBP 3226 induced a slight, but significant inhibition on both the first and second peaked responses.
At a low frequency (1 Hz), the first peak was not influenced by blockade of α1‐adrenoceptors or NPY Y1 receptors with prazosin (0.1 μM) or BIBP 3226 (1 μM), respectively, but abolished by P2X receptor desensitization with α,β‐methylene ATP (αβ‐m ATP, 1 μM). At a high frequency (10 Hz), the first peak was mostly inhibited by αβ‐m ATP and partially by prazosin and BIBP 3226. On the other hand, the second peak at a low frequency was largely decreased by BIBP 3226 and partially by prazosin and αβ‐m ATP, whereas at a high frequency, it was largely attenuated by prazosin and partially by αβ‐m ATP and BIBP 3226.
The results suggest that at a low frequency, the firstly transient constriction of double peaked responses is mainly induced via an activation of P2X‐receptors, whereas at a high frequency, it is mostly mediated by the P2X‐receptors, and partially by α1‐receptors and NPY Y1‐receptors. The secondary prolonged vasoconstriction at frequencies used is predominantly mediated via both α1‐receptor and NPY Y1 receptor activations, and in part by P2X‐receptors. Furthermore, an activation of NPY Y1 receptors may play an important role in evoking the prolonged vasoconstrictor response to longer pulse trains of stimulation at a low frequency, whereas an α1‐adrenoceptor activation exerts a main vasomotor effect for the prolonged response at a high frequency.

British Journal of Pharmacology (2000) 130, 1699–1705; doi:10.1038/sj.bjp.0703484
Induction of reactive astrocytosis and prevention of motoneuron cell death by the I2‐imidazoline receptor ligand LSL 60101
Authors: Casanovas Anna , Olmos Gabriel , Ribera Joan , Assumpció Boronat M , Esquerda Josep E , García‐Sevilla Jesús A 
Published: January 2005

I2‐imidazoline receptors are mainly expressed on glial cells in the rat brain. This study was designed to test the effect of treatment with the I2‐imidazoline selective receptor ligand LSL 60101 [2‐(2‐benzofuranyl)imidazole] on the morphology of astrocytes in the neonate and adult rat brain, and to explore the putative neuroprotective effects of this glial response.
Short‐term (3 days) or chronic (7–10 days) treatment with LSL 60101 (1 mg kg−1, i.p. every 12 h) enhanced the area covered by astroglial cells in sections of facial motor nucleus from neonate rats processed for glial fibrillary acidic protein (GFAP) immunostaining. Facial motoneurons surrounded by positive glial cell processes were frequently observed in sections of LSL 60101‐treated rats. A similar glial response was observed in the parietal cortex of adult rats after chronic (10 days) treatment with LSL 60101 (10 mg kg−1, i.p. every 12 h).
Western‐blot detection of the specific astroglial glutamate transporter GLT‐1, indicated increased immunoreactivity after LSL 60101 treatment in the pons of neonate and in the parietoccipital cortex of adult rats.
In the facial motor nucleus of neonate rats, the glial response after LSL 60101 treatment was associated to a redistribution of the immunofluorescence of the basic fibroblast growth factor (FGF‐2) from the perinuclear area of motoneurons to cover most of their cytoplasm, suggesting a translocation of this mitogenic and neurotrophic factor towards secretion pathways.
The neuroprotective potential of the above effects of LSL 60101 treatment was tested after neonatal axotomy of facial motor nucleus. Treatment with LSL 60101 (1 mg kg−1, i.p. every 12 h from day 0 to day 10 after birth) significantly reduced (38%) motoneuron death rate 7 days after facial nerve axotomy performed on day 3 after birth.
It is concluded that treatment with the I2‐imidazoline selective receptor ligand LSL 60101 provokes morphological/biochemical changes in astroglia that are neuroprotective after neonatal axotomy.

British Journal of Pharmacology (2000) 130, 1767–1776; doi:10.1038/sj.bjp.0703485