bluuebunny/crossref_metadata_2025_split huggingface dataset:
Influence of ETR‐p1/f1 antisense peptide on endothelin‐induced constriction in rat renal arcuate arteries
Authors: Wu Xiaochun , Richards Nicholas T. , Johns Edward J. , Kohsaka Takeo , Nakamura Akio , Okada Hidechika 
Published: January 2005

This study set out to examine the endothelin receptor subtypes mediating vasoconstriction in the rat renal arcuate artery. This was done in isolated vessels 120–200 μm in diameter, incubated with a selective agonist and the novel ‘antisense’ peptide to part of the human endothelinA receptor.
Groups of vessels (n=6) were incubated with increasing concentrations of endothelin‐1 (ET‐1), from 1 to 100 nM, which caused a 65% maximal contraction at the highest dose with an pEC50 of 8.16±0.11 M. By contrast, in six other vessels sarafotoxin 6c over the same dose range gave a minimal contraction (around 5% of maximum).
Preincubation of six vessels with the antisense peptide ETR p1/f1 at 1 μM had no effect on the ET‐1 induced vasoconstriction, in terms of displacement of the concentration‐response curve or the maximal tension achieved by the agonist. In the six vessels exposed to 4 μM ETR p1/f1, there was a significant shift of the concentration‐response curve and a lower pEC50 at 7.78±0.09 M (P<0.05). At the highest concentrations of ETR p1/f1, there was a marked suppression of all responses to ET‐1, which at the maximal concentrations tested, 0.1 μM, only reached some 10% of the maximal achievable contraction.
Increasing ET‐1 concentrations up to 2 μM in vessels incubated with 40 μM ETR‐p1/f1 showed that the blockade could be overcome and that the relationship was shifted to the right (P<0.001) by approximately one log unit with a pEC50 of 7.13±0.11 M. A Schild plot of the data indicated the antagonist to be acting competitively at a single population of receptors.
At the highest concentrations tested, 40 μM, ETR‐p1/f1 had no effect on noradrenaline‐induced contractions, indicating a lack of non‐specific actions.
Together, these data suggest that at the rat renal arcuate artery the endothelinA receptor is the predominant functional receptor mediating contraction. Furthermore, this study has shown the potential usefulness of this novel type of ‘antisense’ peptide in blocking receptor activation.

British Journal of Pharmacology (1997) 122, 316–320; doi:10.1038/sj.bjp.0701388
Effect of the molecular polymorphisms of human paraoxonase (PON1) on the rate of hydrolysis of paraoxon
Authors: Mackness Bharti , Mackness Michael I. , Arrol Sharon , Turkie Wajdi , Durrington Paul N. 
Published: January 2005

The hydrolysis of organophosphate pesticides (OP) and nerve gases by serum paraoxonase (PON1) is an important factor determining their toxicity to mammals including man. The PON1 gene contains 2 polymorphic sites at amino acid positions 55 (L→M) and 192 (G→A, classically defined as the A and B genotypes) which result in several alloenzymes of PON1 in human serum.
The 192 polymorphism has previously been shown to affect PON1 activity. We have investigated the effect of both polymorphisms on the hydrolysis of paraoxon by serum from 279 healthy human subjects.
The 55 polymorphism significantly influenced PON1 activity. MM homozygotes had over 50% less activity towards paraoxon compared to the LL and LM genotypes regardless of the 192 genotype (P<0.001).
Multiple regression analysis indicated that the 192 polymorphism, 55 polymorphism and serum PON1 concentration were responsible for 46, 16 and 13% of the variation in PON1 activity, respectively (all P<0.001). None of the other parameters investigated significantly affected PON1 activity.
Therefore both PON1 polymorphisms affect the hydrolysis of paraoxon. AA/MM and AB/MM individuals may be potentially more susceptible to OP intoxication.
Genotyping individuals for both PON1 polymorphisms may provide a method for identifying those individuals at most risk of OP poisoning. The effect of PON1 polymorphisms on activity may also explain why some Gulf War Veterans have developed Gulf War Syndrome and some have not.

British Journal of Pharmacology (1997) 122, 265–268; doi:10.1038/sj.bjp.0701390
Homocysteine as a modulator of platelet‐derived growth factor action in vascular smooth muscle cells: a possible role for hydrogen peroxide
Authors: Nishio Eisuke , Watanabe Yasuhiro 
Published: January 2005

Homocysteine is an independent risk factor for cardiovascular disease. The mechanisms by which elevated plasma concentrations of homocysteine are related to the pathogenesis of atherosclerosis are not fully understood. Therefore, we examined the effect of homocysteine on cell replication of rat cultured vascular smooth muscle cells (VSMCs) at concentrations similar to those observed in clinical studies.
The incorporation of [3H]‐thymidine was used as a marker of mitosis. Homocysteine (250–500 μM) was a weak mitogen as compared to platelet‐derived growth factor‐BB (PDGF‐BB, 1 nM) and serum (10%), but it potentiated the mitogenic effect of PDGF‐BB four fold at 500 μM. This enhancement of mitogenesis was blunted by the addition of the scavenging enzyme catalase or the antioxidant N‐acetyl‐L‐cysteine.
Furthermore, stimulation of VSMC with homocysteine (25–500 μM) decreased the glutathione peroxidase activity of the cells to 50% of control at 500 μM. Inversely, homocysteine enhanced the superoxide dismutase (SOD) activity to 137% of control at 500 μM, but it had no effect on the catalase activity.
Homocysteine decreased the activity of bovine purified liver cytosolic glutathione peroxidase in a time‐ and dose‐dependent manner. The maximum decrease was 50%.
In summary, homocysteine has a weak mitogenic effect on VSMC, but it dramatically enhances the mitogenic response of PDGF‐BB, presumably by disturbing the activity of antioxidant enzymes.

British Journal of Pharmacology (1997) 122, 269–274; doi:10.1038/sj.bjp.0701391
Differential effect of dexamethasone on interleukin 1β‐ and cyclic AMP‐triggered expression of GTP cyclohydrolase I in rat renal mesangial cells
Authors: Plüss Christoph , Werner Ernst R. , Wachter Helmut , Pfeilschifter Josef 
Published: January 2005

Endogenous synthesis of tetrahydrobiopterin (BH4) is an essential requirement for cytokine‐stimulated nitric oxide (NO) synthesis in rat mesangial cells. GTP cyclohydrolase I, the rate‐limiting enzyme in BH4 synthesis, is expressed in renal mesangial cells in response to two principal classes of activating signals. These two groups of activators comprise inflammatory cytokines such as interleukin (IL)‐1β and agents that elevate cellular levels of cyclic AMP.
We examined the action of the potent anti‐inflammatory drug dexamethasone on GTP cyclohydrolase I induction in response to IL‐1β and a membrane‐permeable cyclic AMP analogue, N6, O‐2′‐dibutyryladenosine 3′‐5′‐phosphate (Bt2cyclic AMP).
Nanomolar concentrations of dexamethasone markedly attenuated IL‐1β‐induced GTP cyclohydrolase I mRNA steady state level as well as IL‐1β‐induced GTP cyclohydrolase I protein expression and enzyme activity. In contrast, dexamethasone did not inhibit Bt2cyclic AMP‐triggered increase in GTP cyclohydrolase I mRNA level and protein expression, and low (1 nM) or high (1 and 10 μM) doses of dexamethasone consistently increased Bt2cyclic AMP‐induced GTP cyclohydrolase activity.
In summary, these results suggest that glucocorticoids act at several levels, critically dependent on the stimulus used, to control GTP cyclohydrolase I expression.

British Journal of Pharmacology (1997) 122, 534–538; doi:10.1038/sj.bjp.0701395
Potentiation by vasopressin of adrenergic vasoconstriction in the rat isolated mesenteric artery
Authors: Noguera I. , Medina P. , Segarra G. , Martínez M. C. , Aldasoro M. , Vila J. M. , Lluch S. 
Published: January 2005

The aim of the present study was to investigate in rat mesenteric artery rings whether low concentrations of vasopressin could modify the contractile responses to noradrenaline and electrical stimulation of perivascular nerves.
Vasopressin (10−10–10−7 M) caused concentration‐dependent contractions (pD2=8.36±0.09). The V1‐receptor antagonist d(CH2)5Tyr(Me)AVP (10−9–10−8 M) produced parallel rightward shifts of the control curve for vasopressin. Schild analysis yielded a pA2 value of 9.83 with a slope of 1.10±0.14.
Vasopressin (3×10 −10 and 10−9 M) caused concentration‐dependent potentiation of the contractions elicited by electrical stimulation (2–8 Hz; 0.2 ms duration for 30 s) and produced leftward shifts of the concentration‐response curve for noradrenaline. The V1‐receptor antagonist induced concentration‐dependent inhibitions of potentiation induced by vasopressin. The selective V1‐receptor agonist [Phe*, Orn8]‐vasotocin (3×10 −10 and 10−9 M) induced potentiation of electrical stimulation‐evoked responses which was also inhibited in the presence of the V1 antagonist (10−8 M). In contrast, the V2‐receptor agonist deamino‐8‐D‐arginine vasopressin (desmopressin 10−8–10−7 M) did not modify the electrical stimulation‐induced responses and the V2‐receptor antagonist [d(CH2)5, D‐Ile*, Ile4, Arg8]‐vasopressin (10−8–10−7 M) did not affect the potentiation evoked by vasopressin.
In artery rings contracted by 10−6 M noradrenaline in the presence of 10−6 M guanethidine and 10−6 M atropine, electrical stimulation (2, 4 and 8 Hz) produced frequency‐dependent relaxations which were unaffected by 10−9 M vasopressin but abolished by 10−6 M tetrodotoxin.
Vasopressin also potentiated contractions elicited by KCl and contractions induced by addition of CaCl2 to KCl depolarized vessels. The augmenting effects were inhibited by the V1 antagonist.
In the presence of the calcium antagonist nifedipine (10−6 M), vasopressin failed to enhance the contractile responses to electrical stimulation, noradrenaline and KCl.
The results demonstrate that low concentrations of vasopressin strongly potentiate the contractions to adrenergic stimulation and KCl depolarization. This effect appears to be mediated by V1 receptor stimulation which brings about an increase in calcium entry through dihydropyridine‐sensitive calcium channels.

British Journal of Pharmacology (1997) 122, 431–438; doi:10.1038/sj.bjp.0701397
Cyclo‐oxygenase isozymes in mucosal ulcerogenic and functional responses following barrier disruption in rat stomachs
Authors: Hirata Takuya , Ukawa Hideki , Yamakuni Hisashi , Kato Shinichi , Takeuchi Koji 
Published: January 2005

We examined the effects of selective and nonselective cyclo‐oxygenase (COX) inhibitors on various functional changes in the rat stomach induced by topical application of taurocholate (TC) and investigated the preferential role of COX isozymes in these responses.
Rat stomachs mounted in ex vivo chambers were perfused with 50 mM HCl and transmucosal potential difference (p.d.), mucosal blood flow (GMBF), luminal acid loss and luminal levels of prostaglandin E2 (PGE2) were measured before, during and after exposure to 20 mM TC.
Mucosal application of TC in control rats caused a reduction in p.d., followed by an increase of luminal acid loss and GMBF, and produced only minimal damage in the mucosa 2 h later. Pretreatment with indomethacin (10 mg kg−1, s.c.), a nonselective COX‐1 and COX‐2 inhibitor, attenuated the gastric hyperaemic response caused by TC without affecting p.d. and acid loss, resulting in haemorrhagic lesions in the mucosa. In contrast, selective COX‐2 inhibitors, such as NS‐398 and nimesulide (10 mg kg−1, s.c.), had no effect on any of the responses induced by TC and did not cause gross damage in the mucosa.
Luminal PGE2 levels were markedly increased during and after exposure to TC and this response was significantly inhibited by indomethacin but not by either NS‐398 or nimesulide. The expression of COX‐1‐mRNA was consistently detected in the gastric mucosa before and after TC treatment, while a faint expression of COX‐2‐mRNA was detected only 2 h after TC treatment.
Both NS‐398 and nimesulide significantly suppressed carrageenan‐induced rat paw oedema, similar to indomethacin.
These results confirmed a mediator role for prostaglandins in the gastric hyperaemic response following TC‐induced barrier disruption, and suggest that COX‐1 but not COX‐2 is a key enzyme in maintaining ‘housekeeping’ functions in the gastric mucosa under both normal and adverse conditions.

British Journal of Pharmacology (1997) 122, 447–454; doi:10.1038/sj.bjp.0701399
Inhibitory effects of (±)‐propranolol on excitation‐contraction coupling in isolated soleus muscles of the rat
Authors: Ha Tuyen N. V. , Fryer Martin W. 
Published: January 2005

The effect of a β‐adrenoceptor antagonist, propranolol, was investigated on excitation‐contraction coupling in small, intact bundles of soleus muscle fibres from the rat.
(±)‐Propranolol significantly inhibited twitch and tetanic tension with IC50 values of 6.7 μM and 3.5 μM, respectively.
(+)‐Propranolol (which has 100 times less β‐blocking activity than the (±) form) was approximately one third as effective as the (±) form at inhibiting isometric tension.
(±)‐Propranolol (20 μM) had no significant effect on the amplitude of caffeine contractures, suggesting that it did not directly inhibit Ca2+ release from the sarcoplasmic reticulum.
The resting membrane potential measured after 15 min perfusion with 20 μM (±)‐propranolol was not significantly different from control. However, this concentration of (±)‐propranolol significantly reduced both the peak amplitude and the maximum rate of rise of the action potential. Both effects were only partially reversible after extensive washing.
(±)‐Propranolol perfusion caused a modest reduction in the amplitude of sub‐maximal K+ contractures at concentrations (5  μM) that markedly depressed tetanic tension.
The results indicate that (±)‐propranolol can decrease isometric tension independently of β‐receptor occupation by (i) reducing the amplitude and rate of rise of the action potential and (ii) by directly inhibiting excitation‐contraction coupling. The relatively low IC50 for the ‘membrane‐stabilizing’ action of propranolol on tetanic tension (3.5 μM), combined with the ability of the drug to accumulate gradually in biological membranes, may contribute to a peripheral component of the tremorolytic and fatigue‐inducing actions of propranolol on skeletal muscle.

British Journal of Pharmacology (1997) 122, 463–468; doi:10.1038/sj.bjp.0701405
Nitroglycerin‐inhibited whole blood aggregation is partially mediated by calcitonin gene‐related peptide–a neurogenic mechanism
Authors: Booth Brian P. , Nolan Timothy D. , Fung Ho‐Leung 
Published: January 2005

The role of the vasculature and calcitonin gene‐related peptide (CGRP) in nitroglycerin (NTG)‐mediated platelet inhibition was studied.
In vitro incubations of CGRP in whole blood induced a dose‐dependent inhibition of platelet aggregation with an IC50 of 62.1 nM.
The platelet inhibition induced by CGRP was blocked by co‐incubation of 0.53 μM CGRP8‐37, as well as 30 μM NG‐nitro‐monomethyl‐L‐arginine (L‐NMMA).
In a separate group of experiments, 100 nM NTG in rat whole blood (WB) induced platelet inhibition of 6.0±1.3% (mean±s.d.), which was enhanced to 77.6±3.5% by the addition of rat aortic tissue (AT) (P<0.001). The inclusion of CGRP8–37 with NTG and AT in WB reduced platelet inhibition to 31.6±6.8% (P<0.01). Incubation of WB and AT with 30 μM L‐NMMA reduced NTG‐induced inhibition of platelet aggregation to 26.4±4.2% (P<0.001).
It is concluded that vascular tissue contributes to the antiplatelet mechanism of action of NTG. Furthermore, NTG apparently evokes the release of CGRP from vascular tissue and this neuropeptide contributes to the antiplatelet actions of NTG.
The antiplatelet activity of CGRP in whole blood is mediated primarily through the activation of nitric oxide synthase.

British Journal of Pharmacology (1997) 122, 577–583; doi:10.1038/sj.bjp.0701408
Selective antagonism of the GABAA receptor by ciprofloxacin and biphenylacetic acid
Authors: Green M. A. , Halliwell R. F. 
Published: January 2005

Previous studies have shown that ciprofloxacin and biphenylacetic acid (BPAA) synergistically inhibit γ‐aminobutyric acid (GABA)A receptors. In the present study, we have investigated the actions of these two drugs on other neuronal ligand‐gated ion channels.
Agonist‐evoked depolarizations were recorded from rat vagus and optic nerves in vitro by use of an extracellular recording technique.
GABA (50 μM)‐evoked responses, in the vagus nerve in vitro, were inhibited by bicuculline (0.3–10 μM) and picrotoxin (0.3–10 μM), with IC50 values and 95% confidence intervals (CI) of 1.2 μM (1.1–1.4) and 3.6 μM (3.0–4.3), respectively, and were potentiated by sodium pentobarbitone (30 μM) and diazepam (1 μM) to (mean±s.e.mean) 168±18% and 117±4% of control, respectively. 5‐Hydroxytryptamine (5‐HT; 0.5 μM)‐evoked responses were inhibited by MDL 72222 (1 μM) to 10±4% of control; DMPP (10 μM)‐evoked responses were inhibited by hexamethonium (100 μM) to 12±5% of control, and αbMeATP (30 μM)‐evoked responses were inhibited by PPADS (10 μM) to 21±5% of control. Together, these data are consistent with activation of GABAA, 5‐HT3, nicotinic ACh and P2X receptors, respectively.
Ciprofloxacin (10–3000 μM) inhibited GABAA‐mediated responses in the vagus nerve with an IC50 (and 95% CI) of 202 μM (148–275). BPAA (1–1000 μM) had little or no effect on the GABAA‐mediated response but concentration‐dependently potentiated the effects of ciprofloxacin by up to 33,000 times.
Responses mediated by 5‐HT3, nicotinic ACh and P2X receptors in the vagus nerve and strychnine‐sensitive glycine receptors in the optic nerve were little or unaffected by ciprofloxacin (100 μM), BPAA (100 μM) or the combination of these drugs (both at 100 μM).
GABA (1 mM)‐evoked responses in the optic nerve were inhibited by bicuculline with an IC50 of 3.6 μM (2.8–4.5), a value not significantly different from that determined in the vagus nerve. Ciprofloxacin also inhibited the GABA‐evoked response with an IC50 of 334 μM (256–437) and BPAA (100 μM) potentiated these antagonist effects. However, the magnitude of the synergy was 48 times less than that seen in the vagus nerve.
These data indicate that ciprofloxacin and BPAA are selective antagonists of GABAA receptors, an action that may contribute to their excitatory effects in vivo. Additionally, our data suggest that the molecular properties of GABAA receptors in different regions of the CNS influence the extent to which these drugs synergistically inhibit the GABAA receptor.

British Journal of Pharmacology (1997) 122, 584–590; doi:10.1038/sj.bjp.0701411
Pharmacokinetic‐pharmacodynamic modelling of the anti‐lipolytic and anti‐ketotic effects of the adenosine A1‐receptor agonist N6‐(p‐sulphophenyl)adenosine in rats
Authors: Van Schaick E. A. , de Greef H. J. M. M. , Langemeijer M. W. E. , Sheehan M. J. , IJzerman A. P. , Danhof M. 
Published: January 2005

The purpose of this study was to develop and validate an integrated pharmacokinetic‐pharmacodynamic model for the anti‐lipolytic effects of the adenosine A1‐receptor agonist N6‐(p‐sulphophenyl)adenosine (SPA). Tissue selectivity of SPA was investigated by quantification of haemodynamic and anti‐lipolytic effects in individual animals.
After intravenous infusion of SPA to conscious normotensive Wistar rats, arterial blood samples were drawn for determination of blood SPA concentrations, plasma non‐esterified fatty acid (NEFA) and β‐hydroxybutyrate levels. Blood pressure and heart rate were monitored continuously.
The relationship between the SPA concentrations and the NEFA lowering effect was described by the indirect suppression model. Administration of SPA at different rates and doses (60 μg kg−1 in 5 min and 15 min, and 120 μg kg−1 in 60 min) led to uniform pharmacodynamic parameter estimates. The averaged parameters (mean±s.e., n=19) were Emax: −80±2% (% change from baseline), EC50: 22±2 ng ml−1, and Hill factor: 2.2±0.2.
In another group, given 400 μg kg−1 SPA in 15 min, pharmacodynamic parameters for both heart rate and anti‐lipolytic effect were derived within the same animal. The reduction in heart rate was directly related to blood concentration on the basis of the sigmoidal Emax model. SPA inhibited lipolysis at concentrations lower than those required for an effect on heart rate. The EC50 values (mean±s.e., n=6) were 131±31 ng ml−1 and 20±3 ng ml−1 for heart rate and NEFA lowering effect, respectively.
In conclusion, the relationship between blood SPA concentrations and anti‐lipolytic effect was adequately described by the indirect suppression model. For SPA a 6 fold difference in potency was observed between the effects on heart rate and NEFAs, indicating some degree of tissue selectivity in vivo.

British Journal of Pharmacology (1997) 122, 525–533; doi:10.1038/sj.bjp.0701412
Role of the Na+/K+‐ATPase in regulating the membrane potential in rat peritoneal mast cells
Authors: Friis U. G. , Praetorius H. A. , Knudsen T. , Johansen T. 
Published: January 2005

The aim of this study was to investigate the effect of the Na+/K+‐ATPase on the membrane potential of peritoneal mast cells isolated from male Sprague‐Dawley SPF‐rats.
Experiments were performed at 22–26°C in the tight‐seal whole‐cell configuration of the patch‐clamp technique by use of Sylgard‐coated patch pipettes (3–6 MΩ). High‐resolution membrane currents were recorded with an EPC‐9 patch‐clamp amplifier controlled by the ‘E9SCREEN’ software. In addition, a charting programme on another computer synchronously recorded at low resolution (2 Hz) membrane potential and holding current (low‐pass filtered at 500 Hz).
Na+/K+‐ATPase activity was measured as the ouabain‐sensitive change in the zero‐current potential. The zero‐current potential in rat peritoneal mast cells measured 2 min after obtaining whole‐cell configuration amounted to 1.7±2.5 mV (n=21). Ouabain (5 mM), a Na+/K+‐ATPase‐inhibitor, had only a very minor effect upon the membrane potential under resting conditions (n=3).
When mast cells were superfused with nominal calcium‐free external solution, the cells hyperpolarized (Δ mV: 20.2±3.8 mV (n=5)). In addition, when the mast cells were preincubated in nominal calcium‐free external solution for 12±1.6 min before whole‐cell configuration, the membrane potential amounted to −53.7±9.8 mV (n=8). A subsequent superfusion with ouabain (5 mM) depolarized the membrane potential (ouabain‐sensitive hyperpolarization (Δ mV): 23.0±8.4 mV (n=8)).
A high intracellular concentration of Na+ ([Na+]i) (26.6 mM) also resulted in hyperpolarization (Δ mV: 20.2±9.1 mV (n=7)), but only when ATP was present. A subsequent superfusion with ouabain (5 mM) repolarized these cells to −1.2±14 mV (ouabain‐sensitive hyperpolarization (Δ mV): 19.7±7.7 mV (n=7)).
The size of the [Na+]i‐dependent hyperpolarization was dose‐dependent. Low [Na+]i (1 mM) had no effect on membrane potential and these cells were unaffected by superfusion with calcium‐free external solution.
These data thus directly confirm that the stimulant effect of calcium‐free external solutions on the ouabain‐sensitive changes in the zero‐current potential, and hence the Na+/K+‐ATPase, is mediated through [Na+]i and that the activity of the Na+/K+‐ATPase can have an important influence on the resting membrane potential in rat peritoneal mast cells.

British Journal of Pharmacology (1997) 122, 599–604; doi:10.1038/sj.bjp.0701414