bluuebunny/crossref_metadata_2025_split huggingface dataset:
Contraction of vascular smooth muscle induced by phorbol 12, 13 dibutyrate in human and rat pulmonary arteries
Authors: Savineau Jean‐Pierre , Marthan Roger , Crevel Huguette 
Published: July 2012

The effect of phorbol 12,13 dibutyrate (PDB) on vascular tone was studied in both human and rat isolated pulmonary arterial strips (HPA and RPA, respectively).
PDB (1 nm to 2 μm) produced slowly developing, sustained and concentration‐dependent contractions in HPA (mean EC50 = 3.5 nm, n = 5) and RPA (mean EC50 = 120 nm, n = 5). The maximal response was 185.6 ± 25% and 207 ± 27.5% (n = 5) of that induced by K+‐rich (80 mm) solution, and 223 ± 34.5% and 176.5 ± 38.6% of the noradrenaline (10 μm)‐induced contraction in HPA and RPA, respectively.
PDB‐induced contractions were not altered either by the presence of atropine (10 μm), propranolol (5 μm), phentolamine (5 μm) or tetrodotoxin (10 μm) in the bathing solution, or by the removal of endothelium from pulmonary arteries.
In HPA, the amplitude of PDB‐induced contractions was significantly reduced by removal of external calcium ions, addition of verapamil (10 μm) or trifluoperazine (TFP, 5 μm) and significantly increased by Bay K 8644 (0.5 μm). In contrast, in RPA, calcium‐free solution and verapamil had only a moderate effect on the maximal PDB‐induced contraction (approximately 20% reduction), whereas Bay K 8644 and TFP had no significant effect. In both HPA and RPA, PDB‐contractions in calcium‐free solutions were not modified by ryanodine (25 μm) or by 8‐(N,N diethylamino)octyl‐3,4,5, trimethoxybenzoate hydrochloride (TMB‐8, 50 μm).
PDB‐induced contractions were inhibited by protein kinase C (PKC) antagonists. The maximal response was decreased by 60 ± 10.5% and 35 ± 11.5% (n = 5) by 1‐(5‐isoquinolinesulphonyl)‐2‐methyl‐piperazine (H7, 50 μm), 70.5 ± 12.2% and 56 ± 18% (n = 5) by phloretin (100 μm) and 80.7 ± 8.4% and 71 ± 14% (n = 5) by staurosporine (25 nm) in HPA and RPA, respectively.
Long term treatment (15–20 h) of arterial strips with phorbol esters (phorbol 12,13 didecanoate, or PDB) abolished the contractile response to subsequent addition of PDB.
These results show that PDB is a potent vasoconstrictor agent in human and rat pulmonary arteries. Unlike the rat, part of the PDB response depends on calcium influx in human preparations. PDB action appears mainly mediated by the activation of protein kinase C. PKC could thus play a major role in the control of vascular pulmonary reactivity.
Sequential release of tumour necrosis factor, platelet activating factor and eicosanoids during endotoxin shock in anaesthetized pigs; protective effects of indomethacin
Authors: Mózes Tibor , Zijlstra Freek J. , Heiligers Jan P.C. , Tak Corné J.A.M. , Ben‐Efraim Shlomo , Bonta Iván L. , Saxena Pramod R. 
Published: July 2012

The effects of indomethacin were investigated on haemodynamics, haematological and blood glucose values, and the release of tumour necrosis factor (TNF), platelet activating factor (PAF) and eicosanoids in anaesthetized pigs receiving 5 μg kg−1 E. coli lipopolysaccharide (LPS) over 60 min into the superior mesenteric artery. The animals were observed for an additional period of 2 h after the termination of LPS infusion.
Eight of the 17 animals infused with LPS and not treated with indomethacin died within 30 min after the beginning of LPS infusion (non‐survivors), while the other 9 survived the experimental period of 3 h though in a state of shock (survivors).
No alterations were observed in plasma concentrations of PAF and eicosanoids (thromboxane B2 (TXB2), 6‐keto prostaglandin F1α (6‐keto PGF1α) and leukotriene B4 (LTB4)) in non‐survivors. However, a marked increase was detected in TNF release. A significant, though transient, increase in concentrations of PAF, TNF and eicosanoids occurred in the survivors. The peak in the concentrations of PAF and TXB2 preceded the maximum in TNF values in survivors.
Another group of 7 LPS‐infused pigs was treated with indomethacin (2 mg kg−1, i.v. bolus 60 min before the start of LPS infusion, followed by a continuous infusion of 3 mg kg−1 h−1). This treatment prevented death and shock despite the high concentrations of circulating TNF and PAF. Concentrations of cyclo‐oxygenase enzyme products were reduced, whereas LTB4 release was not affected. The effect of indomethacin on haemodynamic changes occurred earlier than on cyclo‐oxygenase products.
In another group of 6 pigs indomethacin (2 mg kg−1, i.v.) was given 20–25 min after the start of LPS infusion at which time mean arterial blood pressure (MABP) had decreased below 40 mmHg indicating imminent death. This indomethacin treatment immediately reversed the hypotension, restored the organ perfusion, delayed the haemoconcentration and thrombocytopenia and prevented death. However, TNF and PAF concentrations remained elevated. Concentrations of cyclo‐oxygenase products studied were reduced by the end of the observation period, whereas LTB4 production was unaffected.
The decrease in MABP induced by exogenous PAF was temporarily prevented by indomethacin.
These data indicate that the beneficial effect of indomethacin in LPS‐induced septic shock is related to cyclo‐oxygenase inhibition as well as to a direct vasoconstrictor property of the drug.
Effects of flecainide on isolated vascular smooth muscles of rat
Authors: Pérez‐Vizcaino Francisco , Duarte Juan , Tamargo Juan 
Published: July 2012

The inhibitory effects of flecainide were studied on contractile responses in rat isolated aortae and caudal artery and on spontaneous mechanical activity in portal vein segments.
In rat isolated aorta flecainide, 10−6 m‐5 × 10−4 m, inhibited in a dose‐dependent manner the contractile responses induced by high K (80 mm) and noradrenaline (NA, 10−5 m). These inhibitory actions were observed when flecainide was added before or after the induced contractions and were similar in aortae with or without endothelium.
Contractile responses induced by addition of Ca to Ca‐free high‐K solution were also dose‐dependently inhibited by flecainide (IC50 = 2.5 ± 0.3 × 10−5 m). Moreover, flecainide inhibited the contractile responses elicited by NA in rings incubated in Ca‐free solution.
Flecainide also inhibited the spontaneous mechanical activity in portal vein segments (IC50 = 6.5 ± 0.9 × 10−5 m).
Flecainide, 10−4 m, inhibited 45Ca uptake stimulated by high K or NA without altering 45Ca uptake in resting aortae.
These results indicated that in rat isolated aortae, caudal arteries and portal veins, flecainide inhibited Ca entry through voltage‐operated channels and NA‐induced Ca uptake as well as Ca release from intracellular stores, thus decreasing the availability of intracellular free Ca required for vascular smooth muscle contraction.
Contraction of rat thoracic aorta strips by endothelin‐1 in the absence of extracellular Ca2+
Authors: Itoh Hiroo , Higuchi Haruyuki , Hiraoka Naoto , Ito Masaaki , Konishi Tokuji , Nakano Takeshi , Lederis Karl 
Published: July 2012

Endothelin‐1 (ET‐1) caused a concentration‐dependent contraction of helical strips from rat thoracic aorta in the absence of extracellular Ca2+. The Ca2+‐depleted muscle strips, prepared by three repeated applications of 10−2 m caffeine or 10−6 m noradrenaline in Ca2+‐free buffer, were contracted by 10−8 m ET‐1 in the same manner as non‐treated strips.
In the absence of extracellular Ca2+, 10−7 m phorbol 12‐myristate 13‐acetate (PMA), an activator of protein kinase C, induced a small but sustained contraction of the rat thoracic aorta strips within 60 min. Preincubation of the strips with 10−7 m PMA for 60 min in Ca2+‐free buffer, did not affect the 10−8 m ET‐1‐induced contraction, but decreased the 5 × 10−8 m phorbol 12,13‐dibutyrate (PDB)‐, or the 10−7 m PMA‐induced contraction, and potentiated the contraction induced by 10−8 m urotensin II. Preincubation with 10−8 m ET‐1 (which induced maximum contraction) for 25 min in Ca2+‐free buffer did not change the subsequent contraction induced by PMA (10−7 m) or urotensin II (10−8 m) but gave a somewhat lower maximum tension than in non‐treated strips.
Calyculin‐A, a potent inhibitor of phosphatase, also induced a contraction of the Ca2+‐depleted muscle strips in Ca2+‐free buffer. Preincubation of the strips with ET‐1 (10−8 m) or PMA (10−7 m) decreased the calyculin‐A (3 × 10−8 m)‐induced contraction.
These results suggest that ET‐1 may induce phosphorylation of an unknown protein either without an increase in myoplasmic Ca2+ concentration or, alternatively, with mobilization of intracellular Ca2+ from noradrenaline‐ and caffeine‐insensitive Ca2+ sources, through a mechanism different from that of phorbol ester.
Effects of Org 7797 on early, late and inducible arrythmias following coronary artery occlusion in rats and dogs
Authors: Winslow E. , Campbell J.K. , Barron E. , Marshall R.J. , Muir A.W. 
Published: July 2012

The class Ic steroidal antiarrhythmic agent, Org 7797, was compared with two other Ic agents, flecainide and propafenone for intravenous activity against ischaemia‐related cardiac arrhythmias and for electrophysiological actions in vivo. In addition the haemodynamic effects of Org 7797 were assessed in greyhounds.
Org 7797 (0.5 mg kg−1) significantly reduced the expected incidence of early ischaemia‐induced ventricular fibrillation (VF) in rats and greyhound dogs and at doses of 0.5–1.0 mg kg−1 antagonized reperfusion‐induced arrhythmias. Comparative studies in rats showed Org 7797 to be 2–4 times more potent than flecainide or propafenone.
Org 7797 (0.5 mg kg−1) slowed intracardiac conduction in anaesthetized beagles and again was at least 2–4 times more potent than flecainide or propafenone.
Org 7797 (0.5 and 2.0 mg kg−1), flecainide (1.0 and 2.0 mg kg−1) or propafenone (0.5 and 2.0 mg kg−1), did not significantly prevent induction of tachyarrhythmias (VT) in dogs with 5–6 day old myocardial infarcts although all 3 drugs appeared to prevent induced VF. All 3 drugs (notably fecainide) did however reduce the VT rate.
All 3 drugs (1–2 mg kg−1) suppressed spontaneous tachyarrhythmias in conscious beagle dogs with 1–2 day old infarcts. Propafenone was the least effective.
In an antifibrillatory dose (0.5 mg kg−1), the major haemodynamic effect of Org 7797 was a 10% increase in peripheral vascular resistance. Stroke volume, cardiac output and coronary blood flow were unchanged. In therapeutic doses, Org 7797 was also less negatively chronotropic than flecainide.
It was concluded that Org 7797 is a potent antifibrillatory agent which is haemodynamically well tolerated. Higher doses are required to suppress late ischaemia‐induced tachyarrhythmias which suggest that its antifibrillatory effects are the consequence of an action other than, or in addition to, sodium channel block.
Staurosporine inhibits the extent of acetylcholine receptor recovery from carbachol‐induced desensitization in snake twitch fibres
Authors: Hardwick Jean C. , Coniglio Lisa M. , Parsons Rodney L. 
Published: July 2012

The effect of the protein kinase inhibitor, staurosporine, on the extent and time course of recovery following carbachol‐induced desensitization was studied in snake twitch‐muscle fibres maintained in an isotonic potassium propionate solution and voltage‐clamped to +30mV.
Pretreatment with staurosporine (0.5 μm) decreased the extent of recovery of spontaneous miniature endplate current (m.e.p.c.) amplitudes following desensitization by a sustained application of 540 μm carbachol. Recovery was inhibited by approximately 50% without altering the time course of m.e.p.c. recovery.
Staurosporine also produced a concentration‐dependent (10 nm to 0.5 μm) decrease in the amplitude of a second carbachol‐induced current, following a wash period, as compared to the amplitude of the current produced by the initial carbachol application. Pretreatment with 0.5 μm K252a, another wide spectrum protein kinase inhibitor, also decreased the extent of recovery of the response to a second carbachol application following desensitization.
Staurosporine pretreatment (0.5 μm) had no effect on either the kinetics of receptor‐channel gating or the initial endplate sensitivity to agonist. This was determined by comparing the amplitude of the carbachol (540 μm)‐induced currents and the amplitude and decay rate of m.e.p.cs in control and staurosporine‐treated fibres.
Staurosporine had no effect on the time course of desensitization onset produced during the initial application of 540 μm carbachol or the depth of desensitization produced by the end of a 2–3 min exposure to 540 μm carbachol.
Elevation of the external calcium concentration from 1 to 10 mm during the 540 μm carbachol application completely antagonized the decreased extent of recovery of m.e.p.c. amplitude produced by pretreatment with 0.5 μm staurosporine.
We suggest that phosphorylation of a population of acetylcholine receptors is required for complete recovery from desensitization, and that staurosporine inhibits the protein kinases responsible for this phosphorylation.
We further propose that a transient increase in intracellular calcium, produced by an increase in calcium influx through agonist‐activated endplate channels, stimulates additional protein kinase activity, which in turn, antagonizes the effect of staurosporine‐treatment on recovery.
Cromakalim (BRL 34915) counteracts the epileptiform activity elicited by diltiazem and verapamil in rats
Authors: Popoli P. , Pezzola A. , Sagratella S. , Zeng Y.C. , de Carolis A. Scotti 
Published: July 2012

The effects of BRL 34915 (cromakalim), a potassium channel opener, have been tested on the epileptiform activity elicited by high doses/concentrations of some calcium antagonists in in vivo (diltiazem) and in vitro (diltiazem and verapamil) experiments in rats.
Diltiazem (150–300 mg kg−1, i.p.) induced behavioural and electroencephalographic (EEG) seizures that were completely prevented by cromakalim (10 nmol/10μl, i.c.v.). Whereas, pentobarbitone (5–10 mg kg−1, i.p.) only prevented the behavioural component of the seizures.
In hippocampal slices, verapamil (1.5–2.0 mm) produced, within 30–60 min of perfusion, a CAl epileptiform bursting in 80% of the experiments. This epileptiform activity was prevented by the cromakalim concentration (50 μm) that did not affect the control CAl synaptic transmission per se. Pentobarbitone also prevented verapamil‐induced epileptiform bursting only at the concentration (100 μm) that also reduced control CAl synaptic transmission.
Diltiazem (1.5 mm) produced a biphasic excitatory‐depressant effect within 60 min of perfusion. A CAl epileptiform bursting appeared in 100% of the experiments within 30 min of perfusion. These excitatory effects were followed by a depression phase, characterized by a reduction of the magnitude of CAl excitatory postsynaptic potentials (e.p.s.ps) and population spike.
The diltiazem‐induced epileptiform bursting was prevented by cromakalim at a concentration (50 μm) that did not affect the control CAl synaptic transmission per se. Pentobarbitone also prevented the diltiazem‐induced epileptiform bursting only at a concentration (100 μm) that also reduced the control CAl synaptic transmission. Both cromakalim (50 μm) and pentobarbitone (100 μm) failed to affect the depressant effects of diltiazem on CAl hippocampal area. On the contrary, high (3.3 mm) calcium solutions prevented both the excitatory and the depressant effects of 1.5 mm diltiazem within 60 min.
These data indicate an involvement of potassium currents in the epileptiform activity elicited by high doses of diltiazem and verapamil.
Aggregation of pigment granules in single cultured Xenopus laevis melanophores by melatonin analogues
Authors: Sugden D. 
Published: July 2012

Isolated melanophores were differentiated from aggregates of neural crest obtained from neurula stage Xenopus laevis embryos after 2 days in culture.
Condensation of pigment granules in these cells by melatonin (5‐methoxy N‐acetyltryptamine, aMT) and various novel analogues was monitored with an image analysis system to quantitate the area occupied by pigment in individual cells.
Melanophores exposed to vehicle (a maximum of 0.1% MeOH) showed little (< 5%) change in pigment area. aMT produced a dramatic condensation of pigment granules (EC50 = the concentration producing a half maximal condensation, 9 pm). The response was rapid, reached a maximum (∼80% decrease in pigmented area) by 10 min, and was reversible after removal of aMT from the culture medium.
Aggregation to aMT was blocked by treating melanophores with pertussis toxin (1 μg ml−1, 7h) indicating a role for a guanosine 5′ triphosphate (GTP)‐binding protein in transducing the aMT receptor signal.
Structure‐activity studies indicated that analogues of aMT lacking a side‐chain N‐acyl substituent (5‐methoxytryptamine, MT) or a group at the 5‐position of the indole ring (N‐acetyltryptamine, aT) were unable to induce pigment aggregation (EC50 > 10 μm).
Lengthening the side‐chain N‐acyl group (N‐propionyl, N‐butanoyl) was tolerated to some degree but eventually (N‐valeroyl and larger) activity diminished. Of the 5‐position analogues tested 5‐methoxy (aMT) was by far the most potent.
Halogen substitution in the 6‐position of the indole ring led to some loss of activity as did a 6‐OH substitution. The 6‐OCH3 compound was inactive.
These studies demonstrate the utility of this model in investigations of structure‐activity relationships at the aMT receptor and suggest that it may be a valuable system for determining the transduction mechanisms coupled to the aMT receptor.
Effects of PAF‐antagonists in mouse ear oedema induced by several inflammatory agents
Authors: Merlos M. , Gómez L.A. , Giral M. , Vericat M.L. , García‐Rafanell J. , Forn J. 
Published: July 2012

Several platelet activating factor (PAF)‐antagonists of different chemical structures were tested in the arachidonic acid‐, tetradecanoylphorbol acetate‐, dithranol‐, and benzoic acid‐induced mouse ear oedema models.
Topical application of UR‐10324, UR‐11353, CV‐6209 and WEB‐2086 markedly inhibited ear oedema induced by the four irritants tested, mimicking the profile obtained with dexamethasone. YM‐461 was highly effective only in the dithranol‐induced ear oedema, while BN‐52021 failed to inhibit ear oedema in all models tested.
Leukocyte recruitment into the inflamed ears was prevented by PAF‐antagonists, as measured by myeloperoxidase activity in the supernatants of ear homogenates.
A relationship between PAF‐antagonist and anti‐inflammatory activities was found in some cases, but other mechanisms cannot be excluded to explain the topical anti‐inflammatory effect of these compounds.
Our results suggest that topical formulations containing PAF‐antagonists could be useful in the treatment of some inflammatory skin diseases and provide evidence on the involvement of PAF in these inflammatory processes.
Effects of vasoactive intestinal peptide, helodermin and galanin on responses of guinea‐pig lung parenchyma to histamine, acetylcholine and leukotriene D4
Authors: Conroy Dolores M. , Samhoun Marwa N. , Piper Priscilla J. 
Published: July 2012

The effect of vasoactive intestinal peptide (VIP) was studied on the contractile response of guinea‐pig lung parenchymal strips (GPP) induced by bronchoconstrictor agonists, such as leukotriene D4 (LTD4), histamine and acetylcholine (ACh). This effect of VIP was compared with helodermin, a peptide that is structurally related to VIP, and galanin, another neuropeptide that is thought to co‐exist with VIP.
VIP (10 nm) induced a potent and reversible inhibition of the contractions of GPP induced by LTD4 (1–30 pmol) but did not affect those due to ACh (1–100 nmol) or histamine (1–30 nmol). A ten fold higher concentration of VIP (100 nm) did not further inhibit LTD4‐induced responses or reduce those induced by histamine or ACh.
Helodermin (10 nm) had a similar inhibitory effect on contractions of GPP induced by LTD4 (3–30 pmol) but did not affect contractions induced by histamine (1–10 nmol).
Indomethacin (2.8 μm) and salbutamol (10 nm) significantly reduced responses elicited by LTD4 and histamine but not those due to ACh. A ten fold higher concentration of salbutamol (100 nm) further inhibited the contractions due to LTD4 and histamine and at this concentration responses induced by ACh were inhibited.
VIP (10 nm) and helodermin (10 nm) significantly reduced the LTD4‐induced release of thromboxane A2 (TXA2), measured as TxB2 by radioimmunoassay, from GPP. The smaller release of TxA2 induced by histamine was not significantly reduced in the presence of VIP.
In comparative studies, galanin (10–100 nm) did not affect contractions of GPP induced by either LTD4, histamine or ACh. In contrast to VIP and helodermin, both at 0.1–3 nmol, which induced dose‐related relaxations of guinea‐pig trachea, galanin was inactive on this preparation in doses of up to 3 nmol.
In conclusion, our results show that contractions of GPP induced by LTD4 are more sensitive to inhibition by VIP and helodermin than are contractions due to histamine or ACh. This inhibition appears to be associated with the different contribution of released TxA2 to contractions evoked by the agonists. VIP and helodermin inhibit the cyclo‐oxygenase‐dependent component of the LTD4‐induced response, as in the case of indomethacin.
Endothelin‐1 inhibits pre‐stimulated tracheal submucosal gland secretion and epithelial albumin transport
Authors: Yurdakos E. , Webber S.E. 
Published: July 2012

Endothelin‐1 potently contracts smooth muscle, including that in the airways. However, its effect on airway mucosal function has not so far been studied.
We have used the ferret whole trachea in vitro to examine the effect of endothelin‐1 on tracheal smooth muscle tone, transepithelial potential difference (p.d.), submucosal gland secretion (including lysozyme secretion from serous cells) and active epithelial albumin transport. In addition we have examined the effects of endothelin on submucosal gland secretion and albumin transport pre‐stimulated with the muscarinic agonist methacholine and the α‐adrenoceptor agonist phenylephrine. The effects of the Ca2+ channel blocker nifedipine on the responses to endothelin have also been assessed.
Endothelin (0.1–100 nm) produced concentration‐dependent increases in intraluminal tracheal pressure indicating smooth muscle contraction, and in the negativity of the transepithelial p.d. These effects were partially inhibited by nifedipine (10 μm).
Endothelin (0.01–100 nm) had no significant effect on baseline rates of mucus, lysozyme or albumin outputs, but produced concentration‐dependent reductions in maintained methacholine‐ and phenylephrine‐induced mucus, lysozyme and albumin outputs. In general endothelin was more potent against methacholine‐induced effects. All of the concentration‐response curves for endothelin were shallow and some appeared to be biphasic, suggesting the possibility of more than one mechanism of action of endothelin.
The effects of endothelin (at concentrations > 1 nm) on phenylephrine‐induced mucus volume, lysozyme and albumin outputs were significantly inhibited by nifedipine. Similarly the effect of endothelin (> 1 nm) on methacholine‐induced mucus volume and albumin outputs (but not lysozyme output) was attenuated by nifedipine. The effects of endothelin (at concentrations < 1 nm) on methacholine and phenylephrine‐induced responses were generally not affected by nifedipine.
Thus, endothelin contracts ferret tracheal smooth muscle and increases transepithelial p.d. at least in part by opening dihydropyridine‐sensitive Ca2+ channels. Endothelin does not directly stimulate submucosal gland secretion or epithelial albumin transport, but inhibits methacholine‐ and phenylephrine‐induced secretion and transport. The inhibitory effects produced by higher concentrations of endothelin may be mediated partially by activation of dihydropyridine‐sensitive Ca2+ channels, although the explanation for this is not clear. The mechanism of action of endothelin in attenuating stimulated secretion and epithelial transport at lower concentrations is unknown.;