bluuebunny/crossref_metadata_2025_split huggingface dataset:
Altered thermoregulatory responses to clonidine in streptozotocin‐diabetic rats
Authors: O'Donnell J.M. , Banyasz T. , Kovacs T. 
Published: July 2012

The effects of streptozotocin (STZ) treatment on α2‐adrenoceptor regulation of body temperature were studied by monitoring the response of colonic temperature to administration of clonidine.
A dose‐dependent fall in colonic temperature occurred in control rats given clonidine challenge (0.05‐2.0 mg kg−1, s.c.); this response was inhibited by prior administration of either yohimbine or idazoxan (2 mg kg−1, s.c.) but not by the peripherally‐acting α2‐adrenoceptor antagonist L‐659,066 (10 mg kg−1, s.c.).
In rats treated with STZ (65 mg kg−1, i.v.) administration of clonidine elicited a dose‐independent hyperthermia (circa 1°C.); this effect was unaltered by prior administration of yohimbine or idazoxan.
Naloxone (5 mg kg−1, s.c.) elicited a small fall in temperature(< 1°C.) in both control and STZ‐treated rats; naloxone pretreatment did not alter the temperature response to clonidine in either group.
Nicotinic acid (10 mg kg−1, s.c.) caused a similar small elevation in temperature in both groups.
Administration of replacement insulin to STZ‐treated rats maintained weight gain and low blood glucose while the thermoregulatory response to clonidine slowly reverted to normal.
These results show that altered central temperature control is an element of the generalised abnormality of α2 receptor function induced by STZ.
Properties of the inhibitory junction potential in smooth muscle of the guinea‐pig gastric fundus
Authors: Ohno Naotomo , Xue Lin , Yamamoto Yoshimichi , Suzuki Hikaru 
Published: July 2012

In circular smooth muscle of the guinea‐pig gastric fundus, transmural nerve stimulation evoked a cholinergic excitatory junction potential (e.j.p.), and blockade of the e.j.p. by atropine revealed a non‐adreriergic non‐cholinergic (NANC) inhibitory junction potential (i.j.p.).
The amplitude of the e.j.p. was increased by apamin, suramin or NGnitro‐L‐arginine (L‐NOARG), with no significant change in the membrane potential.
The i.j.p. consisted of two components (fast and slow); apamin inhibited the former, nitroarginine inhibited the latter, and suramin inhibited both components.
Apamin inhibited the hyperpolarization produced by adenosine 5′‐triphosphate (ATP) but not by vasoactive intestinal polypeptide (VIP). Suramin inhibited the hyperpolarization produced by VIP but not by ATP. The sodium nitroprusside (SNP)‐induced hyperpolarization was not blocked by apamin or suramin. L‐NOARG or tetrodotoxin did not inhibit the hyperpolarization produced by ATP, VIP or SNP.
The data did not support the hypothesis that ATP, VIP or nitric oxide (NO) is the main transmitter responsible for generation of the NANC i.j.p. in the fundus.
Actions of L‐NOARG suggest that endogenous NO may be involved in junctional transmission, mainly as an inhibitory modulator of cholinergic transmission.
Characterization of inositol hexakisphosphate (InsP6)3‐mediated priming in human neutrophils: lack of extracellular [3H]‐InsP6 receptors
Authors: Kitchen E. , Condliffe A.M. , Rossi A.G. , Haslett C. , Chilvers E.R. 
Published: July 2012

Inositol hexakisphosphate (InsP6) is a ubiquitous and abundant cytosolic inositol phosphate that has been reported to prime human neutrophils for enhanced agonist‐stimulated superoxide anion generation. This led to the proposal that the release of InsP6 from necrotic cells may augment the functional responsiveness of neutrophils at an inflammatory focus. The aim of this study was to examine whether the functional effects of InsP6 in neutrophils are receptor‐mediated and establish the magnitude of this priming effect relative to other better characterized priming agents.
Analysis of [3H]‐InsP6 binding to human neutrophil membranes in 20 mM Tris, 20 mM NaCl, 100 mM KC1, 5 mM EDTA (pH 7.7) buffer using 0.1 mg ml−1 membrane protein and 2.5 nM [3H]‐InsP6 (90 min, 4°C), demonstrated specific low affinity [3H]‐InsP6 binding that was non‐saturable up to a radioligand concentration of 10 nM.
[3H]‐InsP6 displacement by InsP6 gave a Hill coefficient of 0.55 and best fitted a two‐site logistic model (53% KD 150 nM, 47% KD 5 μm). [3H]‐InsP6 binding also displayed low (3 fold) selectivity for InsP6 over Ins(1,3,4,5,6)P5.
The specific [3H]‐InsP6 binding displayed a pH optimum of 8, was abolished by pre‐boiling the membranes, and was enhanced by Ca2+, Mg2+ and Na+.
In incubations with intact neutrophils, where high levels of specific [3H]‐LTB4 binding was observed, no [3H]‐InsP6 binding could be identified.
Preincubation of neutrophils with 100 μm InsP6 had no effect on resting cell morphology, but caused a minor and transient (maximal at 30 s) enhancement of (0.1 nM) fMLP‐induced shape change (% cells shape changed: fMLP 53±3%, fMLP+InsP6 66±4%). Similarly, InsP6 (100 μm, 30 s) had no effect on basal superoxide anion generation and, compared to lipopolysaccharide (LPS, 100 ng ml−1, 60 min), tumour necrosis factor‐α (TNFα, 200 u ml−1, 30 min) or platelet‐activating factor (PAF, 100 nM, 5 min) caused only a small enhancement of 100 nM fMLP‐stimulated superoxide anion generation (fold‐increase in superoxide anion generation over fMLP alone: InsP6 1.8±0.3, LPS 6.8±0.6, TNFα 5.2±0.7, PAF 5.8±0.6).
While these data support the presence of a specific, albeit low affinity, [3H]‐InsP6 binding site in human neutrophil membrane preparations, the lack of binding to intact cells implies that the functional effects of InsP6 (ie. enhanced fMLP‐stimulated superoxide anion generation and shape change) are not receptor‐mediated.
Endothelin receptors in human coronary artery and aorta
Authors: Bacon C.R. , Davenport A.P. 
Published: July 2012

ETA and ETB‐selective and non‐selective ligands were used to define the endothelin receptors in the media (vascular smooth muscle layer) of human aorta and coronary artery. Saturation experiments with iodinated endothelin‐1 (ET‐1), endothelin‐2 and sarafotoxin 6b (S6b) identified high affinity binding sites in aorta (KD [125I]‐ET‐1 0.33±0.02nM (n=9), KD [125I]‐ET‐2 1.04±0.23 nM (n=5), KD [125I]‐S6b 0.15±0.01 nM (n=9 ±s.e.mean)) and coronary artery (KD [125I]‐ET‐1 0.43±0.10nM, KD [125I]‐ET‐2 0.71±0.17 nM, KD [125I]‐S6b 0.27±0.03 nM (n=3 ±s.e.mean)). Hill coefficients (nH) approached unity in each case.
No specific binding was detectable with [125I]‐ET‐3 (4 pM‐4 nM) in aorta. Unlabelled ET‐3 competed monophasically with [125I]‐ET‐1 in aorta (KD 8.21±1.62 nM, compared to unlabelled ET‐1 KD, 0.60±0.20 nM) (n= 3 ±s.e.mean). In coronary artery, the KD and Bmax values calculated from [125I]‐ET‐3 saturation experiments were 2.13±1.39nM and 20.6±12.9 fmol mg−1 protein, respectively (n=3 ±s.e.mean).
ETA antagonists competed monophasically for [125I]‐ET‐1 (100 pM) binding sites with nanomolar or subnanomolar affinity in the aorta (KD BQ123, 0.47±0.13nM; KD FR139317, 0.40±0.10nM; KD PD151242, 2.09±0.48 nM) and coronary artery (KD FR139317, 0.41±0.13 nM; KD PD151242, 3.60±0.74nM) (n=3 ±s.e.mean). However, two site fits were preferred on analysis of competition experiments with ETB‐selective agonists versus [125I]‐ET‐1 in coronary artery (BQ3020: KDETA 0.96±0.14)μm, KD ETB 1.34±1.08nM and sarafotoxin 6c: KD ETA 1.15±0.14 μm, KD ETB 1.77±0.72nM) (n=3 ±s.e.mean). The selectivity of the agonists for ETB receptors (700 fold) was lower than reported in other species.
Sarafotoxin 6b (2 pM‐2 μm) completely inhibited [125I]‐ET‐1 (100 pM) binding in aorta (KD 1.36±0.22nM) (n=3 ±s.e.mean). The non‐peptide compounds Ro462005 and bosentan, competed with [125I]‐ET‐1 binding in coronary artery with KD values of 0.19±0.04 μm and 2.94±0.95 nM, respectively (n=3 ±s.e.mean).
Inhibition of [125I]‐ET‐2 and [125I]‐S6b binding by FR139317 was similar to the inhibition of [125I]‐ET‐1 binding in both arteries, being monophasic with KD values in the same range.
ETA receptors in coronary artery media were detected by [125I]‐PD151242 (KD 0.23±0.04 nM, Bmax 10.1±1.2 fmol mg−1 protein) (n=3 ±s.e.mean). [125I]‐BQ3020, an ETB‐selective radioligand, indicated the presence of a smaller population of ETB receptors in this tissue (KD 0.60±0.31 nM, Bmax 4.5±2.1 fmol mg−1 protein) (n=3 ±s.e.mean).
Autoradiography with [125I]‐PD151242 and [125I]‐BQ3020 confirmed the predominance of ETA receptors in the media of both arteries.
The results of this study indicate that ETA receptors predominate in the vascular smooth muscle of human cardiac arteries, with a small and variable population of ETB receptors detectable in the coronary artery.
Angiotensin II‐activated Ca2+ entry‐induced release of Ca2+ from intracellular stores in rat portal vein myocytes
Authors: Morel J.L. , Macrez‐Leprêtre N. , Mironneau J. 
Published: July 2012

. The action of angiotensin II (AII) was studied in single myocytes from rat portal vein in which the cytoplasmic Ca2+ concentration was estimated by emission from dyes Fura‐2 or Indo‐1 and the Ca2+ channel current was measured with the whole‐cell mode of the patch‐clamp technique.
. Most of the AII‐evoked increases in [Ca2+]i were reduced by about 60% after pretreatment with ryanodine and caffeine to deplete intracellular Ca2+ stores. However, in some cells the AII‐induced Ca2+ responses were of small amplitude and resembled those obtained in the presence of ryanodine and caffeine. Both types of Ca2+ responses induced by AII were selectively inhibited by losartan, suggesting that the AII effects resulted from activation of the angiotensin AT1 receptors.
. The concentration‐response curve to AII had an EC50 value close to 1 nM for the increase in [Ca2+]i obtained after depletion of intracellular Ca2+ stores. This value was increased to around 18 nM in experiments where the intracellular Ca2+ stores were not depleted.
. AII‐evoked Ca2+ responses were abolished in the absence of external Ca2+ and in the presence of 1 μm oxodipine to block L‐type Ca2+ channels.
. Intracellular applications of the InsP3 receptor antagonist, heparin or an anti‐PdtIns antibody did not modify AII‐induced Ca2+ responses.
. Our results show that AII releases Ca2+ from intracellular stores without involving InsP3 but through a Ca2+ release mechanism activated by Ca2+ influx through L‐type Ca2+ channels.
Effects of dexamethasone and SB 209670 on the regional haemodynamic responses to lipopolysaccharide in conscious rats
Authors: Gardiner S.M. , Kemp P.A. , March J.E. , Bennett T. 
Published: July 2012

. Male (350–450 g) Long Evans rats were chronically instrumented to permit regional haemodynamics to be monitored in the conscious state. In the first experiment, either saline (0.4 ml h−1) or dexamethasone (3 mg kg−1, 125 μg kg−1 h−1) was infused continuously for 24 h, before co‐infusion of lipopolysaccharide of (LPS, 150 μg kg−1 h−1) for 24 h. Dexamethasone prevented the delayed (5–24 h) fall in mean arterial blood pressure (MAP) and the renal and hindquarters vasodilatation seen with LPS infusion alone, but not the initial (about 2 h) fall in MAP or renal vasodilatation. However, at this dose, dexamethasone itself caused a significant rise in MAP and regional vasoconstrictions.
. In the second experiment, dexamethasone at a lower dose (12.5 μg kg−1 h−1) had only slight pressor and vasoconstrictor effects. However, in its presence, infusion of LPS caused a substantial and progressive rise in MAP (maximum at 8 h, + 32±3 mmHg) together with persistent mesenteric and hindquarters vasoconstriction and a transient renal vasodilatation.
. In the third experiment, the non‐selective endothelin antagonist, SB 209670 (600 μg kg−1 h−1), blocked the slight pressor and regional vasoconstrictor effects of the lower dose of dexamethasone. Furthermore, in the presence of dexamethasone and SB 209670, infusion of LPS caused marked, but transient hypotension (nadir at 5 h, —24±2 mmHg) and renal and mesenteric vasodilatation.
. At the end of all experimental protocols, sequential administration of the AT1‐receptor antagonist, losartan, followed by the V1‐receptor antagonist, (+)‐(CH2)5‐0‐Me‐Tyr, vasopressin, caused effects indicating a variable involvement of angiotensin and vasopressin in the maintenance of cardiovascular status.
. Collectively, the results indicate that, in the conscious rat, dexamethasone interacts with vasoconstrictor and vasodilator mechanisms, and hence its influence on the haemodynamic responses to LPS cannot be attributed, simply, to inhibition of the activity of inducible nitric oxide synthase and/or cyclo‐oxygenase‐2.
Endothelin‐1‐induced potentiation of human airway smooth muscle proliferation: an ETA receptor‐mediated phenomenon
Authors: Panettieri Reynold A. , Goldie Roy G. , Rigby Paul J. , Eszterhas Andrew J. , Hay Douglas W.P. 
Published: July 2012

. In this study the mitogenic effects in human cultured tracheal smooth muscle cells of endothelin‐1 (ET‐1), ET‐3, and sarafotoxin S6c (S6c), the ETB receptor‐selective agonist, were explored either alone or in combination with the potent mitogen, epidermal growth factor (EGF).
. In confluent, growth‐arrested human airway smooth, neither ET‐1 (0.01 nM‐1μm) nor ET‐3 (0.001 nM‐1 μm) or S6c (0.01 nM‐1 μm) induced cell proliferation, as assessed by [3H]‐thymidine incorporation. In contrast, EGF (1.6 pM − 16 nM) produced concentration‐dependent stimulation of DNA synthesis (EC50 of about 0.06 nM). The maximum increase of about 60 fold above control, elicited by 16nM EGF, was similar to that obtained with 10% foetal bovine serum (FBS). EGF (0.16‐16 nM) also produced a concentration‐dependent increase in cell counts, whereas ET‐1 (1 − 100 nM) was without effect on this index of mitogenesis.
. ET‐1 (1–100 nM) potentiated EGF‐induced proliferation of human tracheal smooth muscle cells. For example, ET‐1 (100 nM), which alone was without significant effect, increased by 3.0 to 3.5 fold the mitogenic influence of EGF (0.16 nM). The potentiating effect of ET‐1 on EGF‐induced proliferation was antagonized by BQ‐123 (3 μm), the ETA receptor antagonist, but was unaffected by the ETB receptor antagonist BQ‐788 (10 μm).
. Neither ET‐3 (1 − 100 nM) nor S6c (1 − 100 nM) influenced the mitogenic effects of EGF (0.16‐1.6 nM).
. [125I]‐ET‐1 binding studies revealed that on average the ratio of ETA to ETB receptors in human cultured tracheal smooth muscle cells was 35:65 (±3; n=4), confirming the predominance of the ETB receptor subtype in human airway smooth muscle.
. These data indicate that ET‐1 alone does not induce significant human airway smooth muscle cell proliferation. However, it potently potentiated mitogenesis induced by EGF, apparently via an ETA receptor‐mediated mechanism. These findings suggest that ET‐1, a mediator detected in increased amounts in patients with acute asthma, may potentiate the proliferative effects of mitogens and contribute to the airway smooth muscle hyperplasia associated with chronic severe asthma.
Effect of cyclosporin A and analogues on cytosolic calcium and vasoconstriction: possible lack of relationship to immunosuppressive activity
Authors: Russo A. Lo , Passaquin A.‐C. , André P. , Skutella M. , Rüegg U.T. 
Published: July 2012

The full therapeutic potential of the main immunosuppressive drug, cyclosporin A (CsA), is limited because of its side effects, namely nephrotoxicity and hypertension. Several lines of evidence suggest that the origin of both side effects could be CsA‐induced vasoconstriction. However, the underlying molecular mechanisms are not well understood.
Diameter measurements of rat isolated mesenteric arteries showed an increase in noradrenaline‐ and [Arg]8vasopressin‐induced vasoconstriction when arteries were pretreated with CsA.
Measurements in cultured vascular smooth muscle cells (VSMC) of either cytosolic calcium concentration or of 45Ca2+ efflux showed that CsA potentiated the calcium influx to several vasoconstrictor hormones: [Arg]8vasopressin, angiotensin II, endothelin‐1 and 5‐hydroxytryptamine. On the other hand, 45Ca2+ efflux in response to thapsigargin, which depletes calcium from intracellular pools, was not potentiated by CsA. 45Ca2+ uptake was not altered by CsA or by any of the analogues tested.
Time‐course studies in cultured VSMC showed that maximal CsA‐induced Ca2+ potentiation occurred after ca. 20 h and this effect was reversed over approximately the next 20 h.
To investigate the possible role played by the known intracellular targets of CsA, namely cyclophilin and calcineurin, CsA derivatives with variable potencies with respect to their immunosuppressive activity, were tested on the calcium influx to [Arg]8vasopressin. Derivatives devoid of immunosuppressive activity (cyclosporin H, PSC‐833) potentiated calcium signalling, while the potent immunosuppressant, FK520, a close derivative of FK506, and MeVal4CsA, an antagonist of the immunosuppressive effect of CsA did not. The latter compound was unable to reverse the calcium potentiating effect of CsA.
Our results show that CsA increases the calcium influx to vasoconstrictor hormones in smooth muscle cells, which presumably increases vasoconstriction. Loading of the intracellular calcium pools appears not to be involved. Experiments with derivatives of CsA and FK520 suggest that interactions with cyclophilins and calcineurin are not the mechanism involved. This indicates, for the first time, that the immunosuppressive activity can be dissociated from the calcium potentiating effect of CsA in vascular smooth muscle.
Effects of calcium antagonists on endothelin‐1‐induced myocardial ischaemia and oedema in the rat
Authors: Filep János G. , Skrobik Yoanna , Fournier Alain , Földes‐Filep Éva 
Published: July 2012

The effects of the calcium channel blockers, verapamil and nifedipine on myocardial ischaemia and oedema evoked by endothelin‐1 (ET‐1) or IRL 1620, an ETB receptor‐selective agonist were studied in anaesthetized and conscious rats.
Bolus injection of ET‐1 (1 nmol kg−1, i.v.) or IRL 1620 (1 nmol kg−1, i.v.) to conscious chronically catheterized rats evoked a transient depressor response followed by a prolonged pressor effect. Corresponding to changes in blood pressure, a transient tachycardia and a sustained bradycardia were observed. Pretreatment of the animals with verapamil (1 mg kg−1, i.v.) or nifedipine (200 μg kg−1, i.v.) produced on average 5 mmHg decrease in mean arterial blood pressure. Both verapamil and nifedipine inhibited by 63 and 44% the pressor actions of ET‐1 or IRL 1620 (1 nmol kg−1), respectively, and the accompanying bradycardia. Both verapamil and nifedipine potentiated the magnitude of the depressor action of ET‐1 and IRL 1620 without affecting the accompanying tachycardia. Decreasing mean arterial blood pressure with hydralazine (0.2‐0.3 μmol kg−1, i.v.) to levels comparable to those observed after verapamil or nifedipine had no significant effects on the haemodynamic responses to ET‐1 or IRL‐1620.
Intravenous bolus injection of ET‐1 or IRL 1620 (0.1–2 nmol kg−1) into anaesthetized rats produced dose‐dependent ST segment elevation of the electrocardiogram without causing arrhythmias. ST segment elevation developed within 30–50 s and persisted for at least 10–20 min following injection of the peptides.
Pretreatment of the animals with verapamil (1 mg kg−1, i.v.) or nifedipine (200 μg kg−1, i.v.) inhibited on average by 79 and 76% the ST segment elevation elicited by ET‐1 (1 nmol kg−1), respectively. Verapamil and nifedipine also attenuated IRL 1620 (1 nmol kg−1)‐induced ST segment elevation on average by 71 and 74%, respectively. In contrast, no significant inhibition was observed with hydralazine (0.2‐0.3 μmol kg−1).
Both ET‐1 and, to a lesser extent, IRL 1620 (0.1–2 nmol kg−1) evoked albumin accumulation in cardiac tissues in a dose‐dependent fashion as measured by the local extravascular accumulation of Evans blue dye in conscious rats. ET‐1 and IRL 1620 (1 nmol kg−1) enhanced albumin extravasation by 109 and 82%, and 34 and 44% in the left ventricle and right atrium, respectively. ET‐1 or IRL 1620‐induced albumin extravasation was completely prevented by verapamil (1 mg kg−1) or nifedipine (200 μg kg−1) in these vascular beds. In contrast, hydralazine (0.2‐0.3 μmol kg−1) failed to modify the effects of ET‐1 or IRL 1620 on albumin extravasation.
These results show that verapamil and nifedipine are highly effective in protecting the myocardium against the pro‐ischaemic and microvascular permeability enhancing effects of ET‐1 and suggest that ETA and constrictor ETB (tentatively termed ETB2) receptors mediating these actions of ET‐1 are coupled to calcium influx through dihydropyridine‐sensitive calcium channels.
Characterization of Na+ influx mediated by ATP4—‐activated P2 purinoceptors in PC12 cells
Authors: Choi Se‐Young , Kim Kyong‐Tai 
Published: July 2012

Micromolar levels of extracellular ATP increased cytosolic Na+ concentration ([Na+]i) as well as cytosolic Ca2+ concentration ([Ca2+]i) in PC12 cells.
Pretreatment of cells with tetrodotoxin, benzamil or thapsigargin did not alter the ATP‐induced Na+ influx.
Increased extracellular Mg2+ concentration decreased the ATP effect. Furthermore, when the extracellular ATP pool was treated to contain corresponding calculated concentrations of ATP4‐, the increase in [Na+]i stayed linked to the ATP4‐ concentration rather than to the total ATP concentrations in the stimulants.
Extracellular ATP does not create nonselective pores as shown by the fact that ethidium bromide does not enter the cells upon ATP stimulation.
Among the tested nucleotides, only adenosine 5′‐O‐(3‐thiotriphosphate), 2‐methylthio ATP and 2‐chloro ATP also caused Na+ influx.
Reactive Blue 2 specifically decreased the ATP effect in a concentration‐dependent manner.
The results suggest that extracellular ATP triggers Na+ influx through a P2 purinoceptor which is activated by ATP4‐ in PC12 cells.
Inhibition by amphetamine of testosterone secretion through a mechanism involving an increase of cyclic AMP production in rat testes
Authors: Tsai Shiow‐Chwen , Chiao Yu‐Chung , Lu Chien‐Chen , Doong Ming‐Luen , Chen Yen‐Hao , Shih Hsi‐Chang , Liaw Charlie , Wang Shyi‐Wu , Wang Paulus S. 
Published: July 2012

The effect of amphetamine on the secretion of testosterone and the production of testicular adenosine 3′:5′‐cyclic monophosphate (cyclic AMP) in rats was studied.
A single intravenous injection of amphetamine decreased the basal and human chorionic gonadotropin (hCG)‐stimulated levels of plasma testosterone. Plasma LH levels were not altered by the injection of amphetamine.
Administration of amphetamine in vitro resulted in a dose‐dependent inhibition of both basal and hCG‐stimulated release of testosterone.
Amphetamine enhanced the basal and hCG‐increased levels of cyclic AMP accumulation in vitro in rat testes.
These results suggest that amphetamine inhibits the spontaneous and hCG‐stimulated secretion of testosterone from the testes through a mechanism involving an increase in cyclic AMP production.