bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of endotoxin on the angiotensin II receptor in cultured vascular smooth muscle cells
Authors: Burnier Michel , Centeno Gabriel , Waeber Gérard , Centeno Catherine , Bürki Ernst 
Published: July 2012

In some tissues, a decrease in the number of cell surface receptors and alterations of the receptor coupling have been proposed as possible mechanisms mediating the deleterious effects of bacterial endotoxin in septic shock.
The effects of bacterial lipopolysaccharide (Escherichia coli 0111‐B4; LPS) on vascular angiotensin II and vasopressin receptors have been examined in cultured aortic smooth muscle cells (SMC) of the rat by use of radioligand binding techniques.
In vascular SMC exposed to 1 μg ml−1 endotoxin for 24 h, a significant increase in angiotensin II binding was found. The change in [125I]‐angiotensin II binding corresponded to an increase in the number of receptors whereas the affinity of the receptors was not affected by LPS. In contrast, no change in [3H]‐vasopressin binding was observed.
The pharmacological characterization of angiotensin II binding sites in control and LPS‐exposed cells demonstrated that LPS induced an increase in the AT, subtype of the angiotensin II receptors. Receptor coupling as evaluated by measuring total inositol phosphates was not impaired by LPS.
The effect of LPS on the angiotensin II receptor was dose‐, time‐ and protein‐synthesis dependent and was associated with an increased expression of the receptor gene.
The ability of LPS to increase angiotensin II binding in cultured vascular SMC was independent of the endotoxin induction of NO‐synthase.
These results suggest that, besides inducing factors such as cytokines and NO‐synthase, endotoxin may enhance the expression of cell surface receptors. The surprising increase in angiotensin II binding in LPS exposed VSM cells may represent an attempt by the cells to compensate for the decreased vascular responsiveness. It may also result from a non‐specific LPS‐related induction of genes.
JB‐9322, a new selective histamine H2‐receptor antagonist with potent gastric mucosal protective properties
Authors: Palacios Beatriz , Montero Ma Jose , Sevilla Ma Angeles , Roman Luis San 
Published: July 2012

JB‐9322 is a selective histamine H2‐receptor antagonist with gastric antisecretory activity and mucosal protective properties.
The affinity of JB‐9322 for the guinea‐pig atria histamine H2‐receptor was approximately 2 times greater than that of ranitidine.
In vivo, the ID50 value for the inhibition of gastric acid secretion in pylorus‐ligated rats was 5.28 mg kg−1 intraperitoneally. JB‐9322 also dose‐dependently inhibited gastric juice volume and pepsin secretion. In gastric lumen‐perfused rats, intravenous injection of JB‐9322 dose‐dependently reduced histamine‐, pentagastrin‐ and carbachol‐stimulated gastric acid secretion.
JB‐9322 showed antiulcer activity against aspirin and indomethacin‐induced gastric lesions and was more potent than ranitidine.
JB‐9322 effectively inhibited macroscopic gastric haemorrhagic lesions induced by ethanol. Intraperitoneal injection was effective in preventing the lesions as well as oral treatment. The oral ID50 value for these lesions was 1.33 mg kg−1. By contrast, ranitidine (50 mg kg−1) failed to reduce these lesions. In addition, the protective effect of JB‐9322 was independent of prostaglandin synthesis.
These results indicate that JB‐9322 is a new antiulcer drug that exerts a potent cytoprotective effect in addition to its gastric antisecretory activity.
Electrophysiological actions of phenytoin on N‐methyl‐D‐aspartate receptor‐mediated responses in rat hippocampus in vitro
Authors: Laffling Alison J. , Scherr Patrick , McGivern Joseph G. , Patmore Leslie , Sheridan Robert D. 
Published: July 2012

The effects of the anticonvulsant, phenytoin, have been examined on N‐methyl‐D‐aspartate (NMDA) receptor‐mediated population spikes in the CA1 region of the rat hippocampus in vitro.
The ‘conventional’ (AMPA receptor‐mediated) CA1 population spike, evoked by electrical stimulation of the Schaffer collateral/commissural pathway, was abolished by 5 min treatment with 5 × 10−6M 6‐cyano‐7‐nitroquinoxaline‐2,3‐dione (CNQX), after which superfusion with a nominally Mg2+‐free Krebs solution (containing 5 × 10−6 M CNQX) led to the appearance of an epileptiform population spike which was fully developed by 30–40 min.
The epileptiform population spike was abolished by the non‐competitive NMDA antagonist, dizocil‐pine (1 × 10−6 M, 20–30 min) and inhibited by the competitive NMDA receptor antagonist, D‐CPP (IC50 for reducing the amplitude of the first spike in the train = 8.3 × 10−7 M), demonstrating that the response was mediated by activation of NMDA receptors and validating its use as an assay for antagonists acting at the NMDA receptor/channel complex.
Phenytoin (0.1, 0.3 and 1 × 10−4M applied cumulatively for 30 min at each concentration) failed to inhibit the NMDA receptor‐mediated epileptiform population response (n = 7 slices).
Phenytoin (3 × 10−6 M to 1 × 10−4 M) attenuated the effects of the sodium channel activator, veratridine (2 × 10−6M), on the CA1 population spike amplitude (recorded in normal Krebs solution), indicating that the previously observed lack of effect of phenytoin on the NMDA receptor‐mediated response was not due to impaired access of phenytoin to the biophase.
These data support the conclusion that antagonism of NMDA receptor‐mediated events is not a pharmacological property of phenytoin and that such an action is therefore unlikely to contribute to the anticonvulsant activity of this drug.
Modulation of epidermal growth factor effects on epithelial ion transport by intestinal trefoil factor
Authors: Chinery R. , Cox H.M. 
Published: July 2012

The direct epithelial effects of epidermal growth factor (EGF) and its modulation by intestinal trefoil factor (ITF) have been studied in a human colonic adenocarcinoma cell line called Colony‐29 (Col‐29).
When grown in culture as confluent monolayers and voltage‐clamped in Ussing chambers, these epithelia responded with an increase in short circuit current (SCC) to basolateral as well as to apically applied EGF although the latter responses (at 10 nM) were only 25% of those observed following basolateral peptide.
Recombinant rat ITF (added to the basolateral surface) did not alter basal SCC levels, but it did enhance the electrogenic effects of basolateral EGF. The EC50 values for EGF‐induced ion transport were 0.25 nM in control, and 0.26 nM in ITF pretreated Col‐29 epithelia. A significant increase in the size of EGF responses (0.1 nM −10 nM) was observed in the presence of 10 nM ITF and the half‐maximal concentration for this modulatory effect of ITF was 7.6 nM.
The EGF‐induced increases in SCC were partially inhibited (50%) by piretanide pretreatment, indicating that C1− secretion is involved. EGF responses either in the presence or absence of ITF were also significantly reduced (84% and 66% respectively) by the cyclo‐oxygenase inhibitor, piroxicam, therefore implicating prostaglandins as mediators of EGF‐stimulated anion secretion.
We conclude that in confluent Col‐29 epithelia, basolateral EGF stimulates a predominantly prostaglandin‐dependent increase in C1− secretion that is enhanced by basolateral ITF, and that these two peptides may interact in normal and damaged mucosa to alter the local apical solute and fluid environment.
Inhibitory actions of GABA on rabbit urinary bladder muscle strips: mediation by potassium channels
Authors: Ferguson D.R. , Marchant J.S. 
Published: July 2012

The actions of γ‐aminobutyric acid (GABA) upon rabbit urinary bladder muscle were investigated to determine whether they were mediated through potassium channels.
In vitro experiments were undertaken in which bladder muscle strips were caused to contract with carbachol. Addition of GABA or baclofen reduced the size of such evoked contractions in the case of GABA by 20.7 ± 3.2%, in the case of baclofen by 22.4 ± 2.2%.
Electrical stimulation of autonomic nerves in bladder wall strips also evoked contractions which were significantly smaller in potassium‐free Krebs solution. The size of contractions produced by carbachol on the other hand were unaffected by the absence of potassium in the Krebs solution.
The inhibitory actions of GABA and baclofen on carbachol‐induced contractions of bladder muscle were detected at much lower concentrations in potassium‐free compared with potassium containing solutions.
The inhibitory effects of baclofen were completely reversed by tetraethyl ammonium chloride between 1 and 5 mM, caesium chloride between 0.5 and 3 mM and barium chloride between 0.5 and 2.5 mM. The actions of baclofen were only partially reversed by 4‐amino‐pyridine between 1 and 5 mM.
It was concluded that the GABAB receptor‐mediated inhibitory actions on rabbit urinary bladder smooth muscle cells were produced by activation of potassium channels.
Effect of 5‐hydroxytryptamine on the membrane potential of endothelial and smooth muscle cells in the pig coronary artery
Authors: Frieden M. , Beny J.‐L. 
Published: July 2012

Many endothelium‐dependent vasodilators hyperpolarize the endothelial cells in blood vessels. It is not known whether these hyperpolarizations are linked to nitric oxide synthesis or to an endothelium‐derived hyperpolarizing phenomenon, since most of the vasodilators release both factors. In this context, we first verified that the endothelium‐dependent relaxations induced by 5‐hydroxytryptamine (5‐HT) on pig coronary arteries are due only to the activation of the nitric oxide pathway. Then we studied the effects of 5‐HT on membrane potential of endothelial and smooth muscle cells.
In the absence of endothelium, 5‐HT caused a concentration‐dependent contraction of coronary artery strips. No change of the smooth muscle cell membrane potential was observed during contraction to 1 μM 5‐HT.
In the presence of 1 μM ketanserin to suppress the contractile effect of 5‐HT, 5‐HT induced concentration‐dependent relaxation of endothelium‐intact strips precontracted by 10 μM prostaglandin F2α (PGF2α). These relaxations were suppressed by 1 μM NG‐nitro‐L‐arginine, an inhibitor of nitric oxide synthesis, showing that they were produced predominantly by nitric oxide.
In the presence of 1 μM ketanserin, 1 μM 5‐HT did not change the smooth muscle cell membrane potential of strips precontracted by either 10 μM PGF2α or by 10 μM acetylcholine (ACh). In the same conditions, 1 UM 5‐HT caused a weak 2.6 ± 0.4 mV hyperpolarization, of the endothelial cells.
In conclusion, the fact that 5‐HT did not change the membrane potential of smooth muscle cells and only weakly hyperpolarized the endothelial cells during relaxations, suggests that in both cell types no electrical events accompany activation of the nitric oxide pathway. This is in contrast to the hyperpolarizations observed in endothelial and smooth muscle cells when the endothelium‐derived hyperpolarization factor (EDHF) pathway is activated.
Characterization and distribution of putative 5‐ht7 receptors in guinea‐pig brain
Authors: To Z.P. , Bonhaus D.W. , Eglen R.M. , Jakeman L.B. 
Published: July 2012

In the presence of (−)−cyanopindolol (1.0 μM) and sumatriptan (1.0 μM), 0.5 nM [3H]‐carboxamidotryptamine ([3H]‐5‐CT) labelled a single population of receptors in guinea‐pig cerebral cortex membranes.
5‐HT‐displaceable binding was rapid, saturable and reversible. A high affinity binding site was characterized both by equilibrium saturation (Kd = 0.76 ± 0.28 nM; Bmax = 68.1 ± 26.7 fmol mg−1 protein) and kinetic (Kd = 0.18 ± 0.05 nM) analysis. The pharmacological profile of this site was similar to the profile obtained in transfected CHO‐K1 cells expressing guinea‐pig 5‐ht7 receptors.
Autoradiographic analysis revealed a discrete localization of binding sites in guinea‐pig brain, with the highest density of sites in the medial thalamic nuclei and related limbic and cortical regions. Moderate levels of binding were detected in sensory relay nuclei, substantia nigra, hypothalamus, central grey and dorsal raphe nuclei. This distribution corresponded to that observed using in situ hybridization with [35S]‐UTP labelled riboprobes complementary to mRNA encoding the guinea‐pig 5‐ht7 receptor.
In conclusion, under appropriate conditions, [3H]‐5‐CT labelled a single population of saturable binding sites that corresponded to an endogenous 5‐ht7 receptor in guinea‐pig brain. The distribution of 5‐ht7 receptors in thalamocortical and limbic brain regions suggests a role for these receptors in sensory and affective behaviours.
Time‐dependent fading of the activation of KATP channels, induced by aprikalim and nucleotides, in excised membrane patches from cardiac myocytes
Authors: Thuringer Dominique , Cavero Icilio , Coraboeuf Edouard 
Published: July 2012

The effects of the potassium channel opener (KCO) aprikalim (RP 52891) on the nucleotide‐induced modulation of ATP‐sensitive K+ (KATP) channels in freshly dissociated ventricular myocytes of guinea‐pig heart, were studied by use of the inside‐out patch‐clamp technique. The internal surface of the excised membrane patch was initially bathed with a standard solution (Mg2+‐free with EDTA), then sequentially superfused with solutions containing nucleoside diphosphates (NDPs: 200 UM ADP and 50 UM GDP) and NDPs plus 1 mM MgCl2 (with EGTA; referred to as Mg‐NDP solution).
The normalized concentration‐response (channel closing) relationship to ATP was shifted to the right when the standard solution was replaced by the Mg‐NDP solution. Hence, the internal concentration of ATP ([ATP]i) inhibiting the channel activity by half (Ki) increased from 56 UM to 180 μM, with an apparently constant slope factor (s = 2.37). NDPs in the absence of Mg2+ did not decrease the sensitivity of the channels to ATP.
In standard solution, aprikalim (100 μM) activated KATP channels in the presence of a maximally inhibitory [ATP]i (500 μM). This effect was strongly enhanced when aprikalim was applied to patches exposed to Mg‐NDP solution, as demonstrated by the 9 fold increase in Kifor [ATP]i (from 180μM to 1.5 mM and s = 2.37).
The ability of aprikalim to overcome the channel closing effects of ATP in Mg‐NDP solution waned rapidly. Similarly, the NDP‐induced activation of ATP‐blocked channels was also time‐dependent. Both activation processes disappeared before the channel run‐down phenomenon appeared in ATP‐free conditions.
In conclusion, aprikalim is much more potent in opening KATP channels in membrane patches bathed in Mg‐NDP solution than in standard solution. However, under the former experimental conditions, the effect of aprikalim waned rapidly. It is proposed that the waning phenomenon results from changes in the intrinsic enzymatic activity of the KATP channel protein (possibly linked to the experimental conditions) which lead to the channel closure.
Differences in response to 5‐HT4 receptor agonists and antagonists of the 5‐HT4‐like receptor in human colon circular smooth muscle
Authors: Tarn T.S‐F. , Hillier K. , Bunce K.T. , Grossman C. 
Published: July 2012

In isolated circular smooth muscle strips of human colon 5‐hydroxytryptamine (5‐HT) produced a concentration‐related inhibition of spontaneous motility.
The azabicycloalkyl benzimidazolones, BIMU 8 and BIMU 1, which have 5‐HT4 receptor stimulant properties, inhibited motility with EC50 values of 0.76 μM and 3.19 μM respectively and their Emax values were not significantly different from 5‐HT (EC50, 0.13 μM).
The 5‐HT4 receptor antagonist, DAU 6285 (1–10 μM), displaced the 5‐HT concentration‐response curve to the right in a parallel concentration‐dependent manner without depressing the maximum. The Schild plot was linear and the slope did not differ significantly from unity giving a pA2 value of 6.32.
The high affinity selective 5‐HT4 receptor antagonist, GR 113808, at a concentration of 3 nM displaced the 5‐HT concentration‐response curve in a parallel manner giving an apparent pKB estimate of 8.9 ±0.24. However, higher concentrations of 10–100 nM GR 113808 did not result in a further significant displacement of the 5‐HT concentration‐response curve and there was no suppression of Emax.
GR 113808 (10 nM) also caused a parallel displacement of the concentration‐response curve to the 5‐HT4 receptor agonist, 5‐methoxytryptamine (5‐MeOT) giving apparent pKB values ranging from 8.3–9.3.
GR 113808 (3–100 nM) failed to displace 5‐HT or 5‐MeOT concentration‐response curves in tissue strips from 3 patients out of a total of 10 patients studied in whom the response to 5‐HT and 5‐MeOT was normal.
The 5‐HT4 receptor antagonist, SDZ 205–557 (0.3–10 μM), had no significant effect on 5‐HT‐induced inhibition of spontaneous motility.
The present results are discussed in the light of variability of response to GR 113808 and SDZ 205–557 in other tissues.
Overall, our data indicate that human colon circular smooth muscle can be regarded as a site in which 5‐HT4‐like receptors are present but it is as yet unclear whether these results are also an indication of receptor variation.
A study on P2x purinoceptors mediating the electrophysiological and contractile effects of purine nucleotides in rat vas deferens
Authors: Khakh Baljit Singh , Surprenant Annmarie , Humphrey Patrick P.A. 
Published: July 2012

We have studied both the electrophysiological and contractile effects of the purine nucleotide, adenosine‐5′‐triphosphate (ATP), as well as a number of its structural analogues as agonists at P2X purinoceptors in the rat vas deferens in vitro.
Electrophysiological effects were investigated by a whole cell voltage clamp technique (holding potential − 70 mV) with fast flow concentration‐clamp applications of agonists in single isolated smooth muscle cells. ATP, 2‐methylthio adenosine‐5′‐triphosphate (2‐MeSATP) and α, β methylene adenosine‐5′‐triphosphate (αβ‐meATP) all evoked inward currents over a similar concentration range (0.3–10 μM), being approximately equipotent with similar concentrations for threshold effects (0.3 μM). ADP (10 μM) also evoked a rapid current of similar peak amplitude to that seen with ATP (10 μM).
α,β‐meATP was the most potent agonist in producing contractions of the rat vas deferens whole tissue preparation, with a threshold concentration equal to that in the electrophysiological studies (0.3 UM). However, ATP and 2‐MeSATP were at least ten times less potent in studies measuring contraction than in the electrophysiological studies. Furthermore, their concentration‐effect curves were shallow with smaller maximal responses than could be achieved with α,β‐meATP. ADP, AMP and adenosine were inactive at concentrations up to 1 mM. The rank order of agonist potencies observed for contraction was α,β‐meATP≫ATP = 2‐MeSATP.
Measurement of inorganic phosphate (iP), as a marker of purine nucleotide metabolism in the vas deferens whole tissue preparation, indicated that ATP and 2‐MeSATP were rapidly metabolized, whereas α,β‐meATP was stable for up to 2 h. Removal of divalent cations prevented breakdown of ATP and 2‐MeSATP, suggesting that metabolism involved a Ca2+/Mg2+‐dependent enzyme.
It appears that in isolated preparations of rat vas deferens, the low potency of ATP and 2‐MeSATP can be explained by rapid agonist breakdown by ectonucleotidases. However, this is not the case in the single cell studies where the use of rapid concentration‐clamp applications revealed the true potency of the agonists. Under such conditions the three agonists were all equal in potency indicating that the rank order of agonist potencies of α,β‐meATP≫ATP = 2‐MeSATP is not in fact characteristic of smooth muscle P2X‐purinoceptors as commonly believed.
Intrinsic activity of the non‐prostanoid thromboxane A2 receptor antagonist, daltroban (BM 13,505), in human platelets in vitro and in the rat vasculature in vivo
Authors: Bertolino Frédéric , Valentin Jean‐Pierre , Maffre Myriam , Grelac Françoise , Bessac Anne‐Marie , Maclouf Jacques , Delhon André , Levy‐Toledano Sylviane , Patoiseau Jean‐François , Colpaert Francis C. , John Gareth W. 
Published: July 2012

We evaluated the effects of daltroban on (i) human platelet shape change and aggregation in vitro, and (ii) mean systemic and pulmonary arterial pressures (MAP and MPAP, respectively) as well as haematocrit, in anaesthetized, open‐chest Sprague‐Dawley rats, compared with those of a chemically distinct prostanoid thromboxane A2 (TxA2) receptor antagonist, SQ 29,548, and agonist, U‐46619.
In human platelets in vitro, daltroban (10 nM‐100 μM; n = 6 per group) concentration‐dependently induced shape change, attaining at 50 μM, a maximum amplitude of 0.83 ± 0.09 mV representing 46.4 ±4.8% of that evoked by U‐46619 (1.78 ± 0.20 mV at 0.2 μM; n = 9); and inhibited U‐46619‐induced platelet aggregation with an IC50 of 77 (41–161)nM. SQ 29,548 (10 nM‐100 μM; n = 6 per group) failed to evoke any platelet shape change, but potently inhibited U‐46619‐induced platelet aggregation with an IC50< 10nM.
In anaesthetized rats in vivo, daltroban (10–2500 μg kg−1, i.v. infused over 2 min; n = 4–8 per group) produced a bell‐shaped dose‐response curve for MPAP and haematocrit, and evoked maximal increases of 12.7 ± 2.1 mmHg and 5.8 ± 1.5% at 80 μg kg−1 (n = 6) and 630 μg kg−1 (n = 8), respectively (both P<0.05) with ED50S of 20 (16–29) and 217 (129–331) μg kg−1, respectively. By comparison, U‐46619 (0.16–20 fig kg−1, i.v.), induced dose‐dependent increases in MPAP and haematocrit (25.4 ± 1.0 mmHg and 16.1 ±2.9% at the highest dose; n = 12, both P<0.01), with ED50s of 1.8 (1.3‐2.5) and 3.9 (3.5‐5.4) fig kg−1, respectively. Daltroban dose‐dependently increased MAP with a maximum amplitude of 42.2 ±4.4 mmHg at a dose of 80 μkg−1 [ED50 = 94 (64–125) fig kg1], similar to that induced by U‐46619 (41.3 ±9.6 mmHg) at a dose of 0.63 fig kg−1 [ED50 = 0.22 (0.13‐0.24) fig kg−1]. SQ 29,548 (10–2500 μg kg−1, i.v.; n = 4 per group) failed to modify significantly any of these parameters.
Our results clearly demonstrate that daltroban, in a similar manner to the TxA2 analogue, U‐46619, but unlike the TxA2 receptor antagonist, SQ 29,548, exhibits significant intrinsic activity in human platelets in vitro and in the rat vasculature in vivo, possibly through TxA2 receptor activation.