bluuebunny/crossref_metadata_2025_split huggingface dataset:
The α2‐adrenoceptors of the human retinoblastoma cell line (Y79) may represent an additional example of the α2C‐adrenoceptor
Authors: Gleason Marie M. , Hieble J. Paul 
Published: July 2012

In agreement with the literature, correlation of the ability of a series of agonists and antagonists to displace [3H]‐rauwolscine binding shows the α2‐adrenoceptors of HT29 cells, NG108–15 cells, OK cells and homogenates of rat sublingual gland to represent four distinct subtypes.
[3H]‐rauwolscine also bound with high affinity (KD = 0.30 ± 0.10 mm) to a human retinoblastoma cell line (Y79). Specific binding represents 73% of total binding, and a Bmax of 38 ± 1 fmol mg−1 protein was determined.
Correlation of antagonist affinities against [3H]‐rauwolscine with corresponding values in the other four tissue sources showed the Y79 cells to resemble most closely the OK cells, the prototype example of an α2C‐adrenoceptor, with a correlation coefficient of 0.90 and a regression slope of 1.01 being obtained for 10 antagonists in these two systems.
Comparison of KD values for [3H]‐rauwolscine also showed a similarity between the OK cells (0.19 ± 0.07 nm) and Y79 cells.
These data suggest that the human retinoblastoma cell line may represent an additional example of the α2C‐adrenoceptor subtype.
Attenuation of tachykinin‐induced airflow obstruction and microvascular leakage in immature airways
Authors: Tokuyama Kenichi , Yokoyama Tatsuya , Morikawa Akihiro , Mochizuki Hiroyuki , Kuroume Takayoshi , Barnes Peter J. 
Published: July 2012

To study the effect of maturation on substance P (SP)‐ and neurokinin A (NKA)‐induced airflow obstruction and airway microvascular leakage (MVL), we have measured changes in both lung resistance (RL) and extravasation of Evans blue dye in anaesthetized immature (aged 14 ± 1 days) and adult guinea‐pigs (aged 80 ± 3 days).
RL and its recovery after hyperinflation at 5 min were measured for 6 min after i.v. SP (0.2, 1 and 30 nmol kg−1), NKA (1 and 10 nmol kg−1) or vehicle (0.9% NaCl). After measurement of RL, MVL in trachea, main bronchi and intrapulmonary airways was also examined.
The order of potency in inducing airflow obstruction did not change with age (NKA> SP) but immature animals required a larger dose of SP or NKA than adults to cause a significant increase in RL.
The order of potency in inducing airway microvascular leakage was sp> NKA in both immature and adult animals. The amount of extravasated dye after SP was significantly less in immature airways, especially in central airways.
Phosphoramidon (2.5 mg kg−1), a neutral endopeptidase (NEP) inhibitor, significantly increased RL after 0.2 nmol kg−1 SP only in adult airways. Phosphoramidon enhanced the dye extravasation after 0.2 nmol kg−1 SP in both immature and adult airways with a significantly greater amount of dye in adult animals, suggesting that mechanisms other than changes in NEP activity may be responsible for this age‐related difference.
RL after hyperinflation following SP was not correlated with the degree of extravasation of Evans blue dye in immature animals, whereas it was closely correlated in adult animals.
SP and NKA may be less potent in causing both bronchoconstriction and microvascular leakage in immature airways.
Airway oedema caused by microvascular leakage may contribute less in immature airways to airflow obstruction after SP or NKA.
Dependence of endotoxin‐induced vascular hyporeactivity on extracellular l‐arginine
Authors: Schott Cathy A. , Gray Gillian A. , Stoclet Jean‐Claude 
Published: July 2012

The dependence on extracellular l‐arginine of vascular hyporeactivity induced by bacterial lipopolysaccharide (LPS) was studied in vivo in rats infused with LPS and in vitro in endothelium‐denuded rat thoracic aortic rings exposed to LPS.
Infusion of LPS during 50 min at a dose of 10 mg kg−1 h−1 produced a significant impairment of the pressor effect of noradrenaline, while in tissues collected 60 min after the start of LPS infusion, no significant alteration in either plasma arginine concentration or aortic arginine content was found compared to saline‐infused controls (where plasma arginine was 78.5 ± 7 μm and aortic arginine 394 ± 124 nmol g−1 tissue).
Incubation of isolated, endothelium‐denuded aortic rings with LPS (10 μg ml−1) in the absence of l‐arginine for 4 h at 37°C produced a 6 fold (P < 0.01) rightward shift in the noradrenaline concentration‐effect curve compared to polymyxin B (1 μg ml−1, a LPS neutralizing agent) and reduced by 15% the maximum observed tension.
The presence of l‐arginine (100 μm) during the incubation with LPS and throughout the following contraction experiments caused a 15 fold (P < 0.01) increase in the EC50 of noradrenaline and greater depression (45%) of the maximum observed tension compared to polymyxin B‐treated controls. Responses in control, non LPS‐treated rings were unaffected by the presence of l‐arginine.
The addition of l‐arginine to rings incubated with LPS in the absence of l‐arginine and maximally precontracted with noradrenaline (10 μm) induced a dose‐dependent relaxation. The EC50 of l‐arginine was 8.0 ± 0.3 μm.
The reactivity of LPS‐treated rings to noradrenaline both in the absence and presence of l‐arginine was restored to control levels by NG‐nitro‐l‐arginine methyl ester (l‐NAME, 300 μm), an inhibitor of NO production and by methylene blue (3 μm), an inhibitor of guanylate cyclase.
Incubation of isolated aortae in the absence of l‐arginine did not significantly decrease the tissue arginine content, whether LPS (10 μg ml−1) was present or not. Similarly, the presence of l‐arginine (100 μm) in the incubation medium did not modify the tissue arginine content.
These results show that the LPS‐induced impairment of vasoconstriction elicited by noradrenaline is dependent on extracellular l‐arginine, although the tissue arginine content is not depleted after LPS pretreatment, and that circulating l‐arginine is sufficient to activate maximally the vascular l‐arginine/NO pathway in endotoxaemic rats.
Comparison of the effects of selective inhibitors of phosphodiesterase types III and IV in airway smooth muscle with differing β‐adrenoceptor subtypes
Authors: Tomkinson Adrian , Karlsson Jan‐Anders , Raeburn David 
Published: July 2012

The relaxant properties of the type IV adenosine 3′,5′‐cyclic monophosphate phosphodiesterase (cyclic AMP PDE) inhibitor, rolipram and the β2‐selective and non‐selective β‐adrenoceptor agonists salbutamol and isoprenaline, were compared on the guinea‐pig, bovine, and mouse trachea and porcine bronchus all precontracted with methacholine (EC30).
Rolipram and both β‐agonists produced concentration‐dependent reversal of the methacholine‐induced tone in the four airway preparations.
Isoprenaline and salbutamol were similar in potency on the guinea‐pig (−log10IC50:8.43, 8.06) and bovine (−log10 IC50:8.52, 8.40) airways. In contrast, salbutamol was much less potent than isoprenaline on the mouse trachea (> 1000 fold) and the porcine bronchus (> 100 000 fold).
The potency of rolipram approached that of isoprenaline on the guinea‐pig and bovine trachea (β2‐adrenoceptors predominate). However, rolipram was significantly less active than isoprenaline on the porcine bronchus (1000 fold) and mouse trachea (> 2000 fold) where β2‐adrenoceptors predominate.
Siguazodan, the type III cyclic AMP PDE inhibitor, produced concentration‐dependent relaxations of the porcine bronchus and guinea‐pig trachea contracted with methacholine. Siquazodan was 100 fold more active than rolipram in pig tissues indicating the type III isoenzyme may be of greater functional significance in this tissue. In contrast, siguazodan was 15 times less potent that rolipram in guinea‐pig airways suggesting a greater role for the type IV PDE.
These findings may reflect a possible relationship between the β2‐adrenoceptor subtype and the functional importance of the type IV PDE isoenzyme. A similar relationship may exist between β1‐adrenoceptors and the PDE type III isoenzyme.
The local anti‐inflammatory action of dexamethasone in the rat carrageenin oedema model is reversed by an antiserum to lipocortin 1
Authors: Duncan G.S. , Peers S.H. , Carey F. , Forder R. , Flower R.J. 
Published: July 2012

A local pre‐injection of 1 μg dexamethasone sodium phosphate strongly inhibited (> 60% inhibition at 3 h; P < 0.001 at all time points) the development of carrageenin‐induced paw oedema in the rat induced by a subplantar injection of 0.1 ml, 2% carrageenin.
Coinjection of a polyclonal rabbit antiserum raised against human 1–188 recombinant lipocortin 1, which also recognised the rat protein, reversed the inhibitory action of dexamethasone (P < 0.05 at 4 h and 5 h). At the highest volume used (40 μl) control antisera were without any effect.
These data further support the concept that lipocortin 1 is involved in the anti‐inflammatory mechanism of action of the glucocorticoids.
Sympathetic innervation and α‐adrenoceptor profile of blood vessels in the posterior region of the rabbit knee joint
Authors: Najafipour Hamid , Ferrell William R. 
Published: July 2012

Experiments were performed to determine the nature of adrenoceptors mediating neurally‐induced vasoconstriction of blood vessels in the posterior region of the rabbit knee joint capsule.
Electrical stimulation of the posterior articular nerve resulted in frequency‐dependent vasoconstriction which was maximal at 10 Hz. This response was mediated predominantly by α2‐adrenoceptors as it was only slightly reduced by prazosin administration and was not only abolished but converted into a dilator response by the α2‐adrenoceptor antagonist rauwolscine. Further experiments with another specific α1‐adrenoceptor antagonist YM‐12617 showed that the frequency‐response curve in the presence of this antagonist did not differ significantly from control.
Neurally‐induced vasoconstriction did not appear to have a purinergic component as it was unaffected by the P2x‐purinoceptor desensitiser α,β methylene ATP.
The rank‐order of potency of α‐adrenoceptor agonists given as a bolus by close intra‐arterial injection was: adrenaline = UK‐14304 > clonidine > phenylephrine, suggesting that the vasoconstrictor effects were mediated predominantly by postjunctional α2‐adrenoceptors.
The α2‐adrenoceptor antagonist rauwolscine converted the constrictor response to close intra‐arterial injection of adrenaline into a dilator response. The vasoconstrictor responses to UK‐14304, clonidine and phenylephrine were substantially inhibited by rauwolscine. The α1‐adrenoceptor antagonist prazosin failed to inhibit the vasoconstrictor responses to adrenaline, clonidine and UK‐14304 and resulted in enhancement of their constrictor effects.
The enhancement of the responses to the α1 and α2 agonists by prazosin appeared to be specifically related to this agent as administration of YM‐12617 did not show such enhancement. The dose‐response curves to both clonidine and UK‐14304 in the presence of YM‐12617 did not differ significantly from control responses. Responses to phenylephrine were significantly reduced by YM‐12617, indicating the presence of post‐junctional α1‐adrenoceptors.
These results show almost complete reversal of the adrenoceptor profile compared to results obtained in an earlier in vitro study, where responses were mediated predominantly by α1‐adrenoceptors with a small population of postjunctional α2‐adrenoceptors (Ferrell & Khoshbaten, 1989). This suggests that the differing environment in vitro may not completely reflect the conditions prevailing in vivo.
Identification of a novel calcium antagonist binding site in rat brain by SR 33557
Authors: Kenny Barry A. , Fraser Stuart , Speeding Michael 
Published: July 2012

In K+‐depolarized taenia preparations from guinea‐pig caecum SR 33557 was a potent antagonist of Ca2+‐induced contractions and antagonized the effect of the calcium channel activator Bay K 8644.
SR 33557 displayed high affinity (pKi 9.54 ± 0.04, nH 1.01) for the [3H]‐(±)‐PN 200‐110 binding site in rat cerebral cortex membranes. In the presence of 5 mm Ca2+ this affinity was reduced (pKi 8.82 ± 0.01, nH 1.05) whilst the affinity of nitrendipine was unaffected by this concentration of Ca2+.
Saturation binding experiments in rat cerebral cortex carried out in the absence and presence of SR 33557 (0.1–1.0 nm) indicated an apparently competitive interaction at the dihydropyridine site, in that SR 33557 reduced the KD of [3H]‐(±)‐PN 200‐110 binding without any effect on Bmax. In kinetic experiments, the rate of dissociation of [3H]‐(±)‐PN 200‐110 from rat cerebral cortex was unchanged in the presence of SR 33557 (5 nm).
d‐cis‐diltiazem fully reversed the inhibition [3H]‐nitrendipine binding to rat cerebral cortex produced by SR 33557 indicating the site of action of SR 33557 to be distinct from the dihydropyridine (DHP) binding site.
Saturation analysis indicated that [3H]‐SR 33557 (0.01–0.8 nm) labelled a single class of binding sites in rat cerebral cortex membranes with high affinity (KD 0.12 ± 0.01, Bmax 222 ± 20 fmol mg−1 protein), although kinetic data indicated the existence of negative cooperativity between the binding sites.
In competition studies, a variety of different calcium antagonists displayed similar affinity for [3H]‐SR 33557 and [3H]‐(±)‐PN 200‐110 sites. The [3H]‐SR 33557 site was sensitive to the inhibitory effect of divalent cations. The affinity of Cd2+ was 0.026 ± 0.015 mm and the rank order of affinity was Cd2+ > Ca2+ > Mn2+ > Mg2+ > Na+.
We propose that SR 33557 labels a distinct site in rat cerebral cortex. The coupling between the SR 33557 and DHP site appears to be very close, resulting in apparently competitive interactions in some experimental protocols but can be revealed as negatively allosteric in other circumstances.
Neurokinin‐induced changes in pial artery diameter in the anaesthetized guinea‐pig
Authors: Beattie D.T. , Stubbs C.M. , Connor H.E. , Feniuk W. 
Published: July 2012

The effects of selective neurokinin agents on pial artery diameter, measured with an on‐line image analyser, have been studied in anaesthetized guinea‐pigs in order to characterize the neurokinin receptors present on pial arteries.
Perivascular injection of either substance P (0.01–1 μm) or the selective NK1 receptor agonists, substance P methyl ester (SPOMe, 0.01–1 μm) and GR73632 (0.1 μm), increased pial artery diameter.
In contrast, the selective NK2 receptor agonist, GR64349 (1 μm), produced a small vasoconstriction while the NK3 receptor‐selective agonist, senktide (1 μm) was inactive.
Co‐administration of GR82334 (1 μm), a selective NK1 receptor antagonist, inhibited the vasodilatation produced by SPOMe (0.1 μm) but not that caused by calcitonin gene‐related peptide (CGRP, 0.01 μm).
The results are consistent with an involvement of NK1 receptors in the neurokinin‐induced increase in guinea‐pig pial artery diameter.
Influences of the endothelium and hypoxia on neurogenic transmission in the isolated pulmonary artery of the rabbit
Authors: MacLean Margaret R. , McCulloch K.M. , MacMillan J.B. , McGrath J.C. 
Published: July 2012

The effects of nitric oxide (10−6 m), Nω‐nitro‐l‐arginine methylester (l‐NAME, 10−4 m, an inhibitor of nitric oxide synthase), endothelium removal, hypoxia and selective α‐adrenoceptor antagonists on responses to nerve electrical field‐stimulation (EFS) were studied in the rabbit isolated pulmonary artery.
EFS induced frequency‐dependent contractions which were abolished by prazosin (α1‐adrenoceptor antagonist) and unaffected by rauwolscine (α2‐adrenoceptor antagonist). EFS‐induced responses were potentiated by l‐NAME and inhibited by nitric oxide. The effect of l‐NAME was reversed by the presence of l‐arginine (2 × 10−4 m), which had no effect on its own. In the presence of l‐NAME, the EFS‐induced responses were reduced by rauwolscine and the residual responses were abolished by prazosin.
Removal of the vascular endothelium increased the maximum contractile response to EFS but did not inhibit the ability of l‐NAME to potentiate contractile responses to EFS.
Hypoxia inhibited the contractile response to EFS. This effect of hypoxia was also seen in the presence of l‐NAME and in endothelium rubbed preparations.
In conclusion, the endothelium modulates EFS‐induced contractions in the rabbit pulmonary artery. The contraction induced by EFS was inhibited by nitric oxide, but potentiated by the nitric oxide‐synthase inhibitor, l‐NAME. The effect of l‐NAME was not mediated solely through the endothelium and revealed involvement of α2‐adrenoceptors in EFS‐induced contraction. Hypoxia inhibited neurogenic responses in rabbit isolated pulmonary arteries.
Conversion of glyceryl trinitrate to nitric oxide in tolerant and non‐tolerant smooth muscle and endothelial cells
Authors: Salvemini Daniela , Pistelli Alessandra , Vane John 
Published: July 2012

Exposure of smooth muscle cells (SMC) to glyceryl trinitrate (GTN, 75–600 μm) for 30 min led to a concentration‐dependent increase in nitrite (NO2−), one of the breakdown products of nitric oxide (NO). This was not affected by 30 min pretreatment of the cells with 0.5 mm of sulphobromophthalein (SBP) an inhibitor of glutathione‐S‐transferase (GST), by metyrapone or SKF‐525A inhibitors of cytochrome P450. These experiments were confirmed by organ bath studies using rabbit aortic strips denuded of endothelium and contracted with phenylephrine. Thus, a 30 min incubation of the strips with 0.5 mm SPB, metyrapone or SKF‐525A did not affect the relaxations in response to GTN (10−10−10−6 m).
Potentiation of the anti‐platelet effect of GTN (44 μm) by endothelial cells (EC, 40 × 103 cells) was not affected by prior incubation of EC with SBP, metyrapone or SKF‐525A (all at 0.5 mm).
Potentiation of the antiplatelet activity of GTN (11–352 μm) by small numbers of SMC (24 × 103 cells) or EC (40 × 103 cells) treated with indomethacin (10 μm) was attenuated when the SMC or EC were treated in culture with a high concentration of GTN (600 μm) for 18 h beforehand (referred to as ‘tolerant’ cells). In addition, tolerant SMC produced far less NO2− than non‐tolerant SMC.
Exposure of non‐tolerant SMC or EC (105 cells) to GTN (200 μm) for 3 min increased (3–4 fold) the levels of guanosine 3′:5′‐cyclic monophosphate (cyclic GMP). This increase was much less (≤ 1 fold) in the tolerant SMC or EC (105 cells). The basal levels of cyclic GMP were similar in normal or tolerant SMC or EC. Sodium nitroprusside (80 μm) or atrial natriuretic factor (ANF, 10−7 m) increased the levels of cyclic GMP in normal or tolerant SMC or EC to the same extent.
The anti‐platelet effects of GTN (44 μm) were potentiated by the sulphydryl donor N‐acetylcysteine (NAC, 0.5 mm). Incubation of GTN (150–1200 μm) for 30 min with NAC (0.1–1 mm) led to a concentration‐dependent increase in NO2− formation. The reduced ability of tolerant SMC or EC to potentiate the anti‐platelet activity of GTN was restored by NAC (0.5 mm). These anti‐aggregatory effects were abolished by concurrent co‐incubation with oxyhaemoglobin (10 μm) indicating that they were due to NO release.
Thus, in SMC or EC, metabolism of GTN to NO does not depend on glutathione‐S‐transferase or the cytochrome P450 system. Furthermore, when compared to normal cells, tolerant SMC or EC metabolize GTN to NO less effectively as assessed by the reduced capacity to potentiate the antiplatelet effects of GTN, to release NO2− and to increase the level of cyclic GMP. This decrease in NO formation shows that tolerance to GTN is mainly due to impaired biotransformation of GTN to NO. NAC, by directly forming NO from GTN, compensates for this failing mechanism.
Histamine H1‐receptor‐mediated inositol phospholipid hydrolysis in DDT1MF‐2 cells: agonist and antagonist properties
Authors: White Teresa E. , Dickenson John M. , Hill Stephen J. 
Published: July 2012

The effect of histamine H1‐receptor stimulation on inositol phospholipid hydrolysis has been investigated in the hamster vas deferens smooth muscle cell line, DDT1MF‐2.
Histamine (EC50 = 27 μm) stimulated the accumulation of [3H]‐inositol phosphates in DDT1MF‐2 cells prelabelled with [3H]‐myo‐inositol. 2‐Thiazolylethylamine (EC50 42 μm) produced a maximal response of similar magnitude to histamine while the maximal response obtained with Nα‐methylhistamine (EC50 = 72 μm) and 2‐pyridylethylamine (EC50 = 85 μm) were much lower (circa 65%, histamine = 100%).
The H1‐selective agonists 2‐(3‐fluorophenyl)‐histamine (2‐FPH) and 2‐(3‐chlorophenyl)‐histamine (2‐CPH) both appeared to act as partial H1‐agonists in this system. Both compounds produced maximal responses of only 30% (with respect to histamine = 100) and were able to antagonize the inositol phosphate response to histamine (estimated Kp = 10.4 and 18.9 μm for 2‐FPH and 2‐CPH respectively).
The response to histamine was antagonized by the H1‐antagonists, mepyramine (KD 0.4 nm), (+)‐chlorpheniramine (KD 1.2 nm) and promethazine (KD 0.3 nm). Furthermore, the (−)‐isomer of chlorpheniramine was approx. three orders of magnitude less potent than the corresponding (+)‐isomer.
The response to histamine (0.1 mm) was not altered by prior treatment of cells with pertussis toxin (100 ng ml−1; 24 h) whereas the inositol phosphate response to adenosine A1‐receptor stimulation in this cell line was significantly attenuated under these conditions.
These data indicate that histamine‐stimulated inositol phospholipid hydrolysis in DDT1MF‐2 cells is mediated via a classical H1‐receptor. Furthermore, the results also suggest that histamine H1‐ and adenosine A1‐receptors activate phospholipase C in DDT1MF‐2 cells via two different G‐protein‐coupled pathways.
Charybdotoxin‐sensitive K+ channels regulate the myogenic tone in the resting state of arteries from spontaneously hypertensive rats
Authors: Asano Masahisa , Masuzawa‐Ito Kaoru , Matsuda Tomohiro 
Published: July 2012

To determine the possible role of Ca2+‐activated K+ (KCa) channels in the regulation of resting tone of arteries from spontaneously hypertensive rats (SHR), the effects of agents which interact with these channels on tension and 86Rb efflux were compared in endothelium‐denuded strips of carotid, femoral and mesenteric arteries from SHR and normotensive Wistar‐Kyoto rats (WKY).
Strips of carotid, femoral and mesenteric arteries from SHR exhibited a myogenic tone; that is, the resting tone decreased when either the Krebs solution was changed to a 0‐Ca2+ solution or 10−7 m nifedipine was added.
The addition of charybdotoxin (ChTX, 10−9−10−7 m), a blocker of large conductance KCa channels, to the resting strips of these arteries produced a concentration‐dependent contraction, which was significantly greater in SHR than in WKY. Relatively low concentrations of tetraethylammonium (0.05–5 mm) produced a concentration‐dependent contraction which was similar to the ChTX‐induced contraction in these strips.
The ChTX‐induced contractions in SHR were greatly attenuated by 10−7 m nifedipine and by 3 × 10−6 m cromakalim, a K+ channel opener. Cromakalim alone abolished the myogenic tone in SHR.
The addition of apamin (a blocker of small conductance KCa channels, up to 10−6 m), or of glibenclamide (a blocker of ATP‐sensitive K+ channels, up to 5 × 10−6 m), to the resting strips failed to produce a contraction.
In resting strips of carotid, femoral and mesenteric arteries preloaded with 86Rb, the basal 86Rb efflux rate constants were significantly greater in SHR than in WKY. The addition of 10−7 m nifedipine to the resting strips decreased the basal 86Rb efflux rate constants only in SHR.
The cellular Ca2+ uptake in the resting state of carotid and femoral arteries from SHR was significantly increased when compared to WKY, and this increase in SHR was significantly reduced by 10−7 m nifedipine.
These results suggest that the ChTX‐sensitive KCa channels were highly activated to regulate the myogenic tone in the resting state of carotid, femoral and mesenteric arteries from SHR. The increased KCa channel functions in SHR arteries appeared to be secondary to the increased Ca2+ influx via L‐type voltage‐dependent Ca2+ channels in the resting state of these arteries.