bluuebunny/crossref_metadata_2025_split huggingface dataset:
α1‐Adrenoceptor vasoconstriction in the tail artery during ageing
Authors: Vila Elisabet , Vivas Nuria M , Tabernero Antonia , Giraldo Jesús , Arribas Silvia M 
Published: August 2006

We have studied the α1‐adrenoceptor‐mediated responses in intact tail artery rings from 3–4 and 20–22 months old Sprague‐Dawley rats, focusing on possible endothelial alterations. The influence of nitric oxide released by the endothelium, the number of α1‐adrenoceptors and the functional receptor reserve were evaluated to determine their contribution to the contractile response mediated by this receptor. The state of the endothelial layer was assessed by confocal microscopy.
Noradrenaline (1 nM–100 μM) induced concentration‐dependent vasoconstriction. The maximum contractions to noradrenaline (P<0.05) and to 75 mM KCl (P<0.01) were higher in young than in old animals.
The density (Bmax) of α1‐adrenoceptors and the dissociation constant (KD) obtained in [3H]‐prazosin binding experiments were unchanged by age.
The apparent affinity (pKA) and the percentage of functional receptors (qx100) remaining after phenoxybenzamine (0.03 μM) were similar in both age groups.
After partial α1‐adrenoceptor inactivation with phenoxybenzamine, NG‐nitro‐L‐arginine methylester (30 μM) significantly potentiated the E/[A] curve to noradrenaline in young rats. However, only responses to 0.1 to 1 μM noradrenaline were significantly potentiated in old animals. In addition, 94% of the vessels from young, but only 52% from old rats were relaxed by 80–100% of the noradrenaline (0.03 μM) contraction, with 1 μM acetylcholine.
No modifications in the area (μm2) or in the number of endothelial nuclei (per mm2) were observed between age groups. An elongation of the nuclei of endothelial cells was observed in the old animals.
These data suggest that the noradrenaline‐induced contraction is decreased in old rats probably due to differences in either the contractile machinery or postreceptor mechanisms. These alterations may be accompanied by an impairment of the release or production of NO from endothelial cells.
Effects of an orally active non‐peptide bradykinin B2 receptor antagonist, FR173657, on plasma exudation in rat carrageenin‐induced pleurisy
Authors: Majima Masataka , Kawashima Noriko , Hiroshi Ito , Katori Makoto 
Published: August 2006

Effects of an orally active non‐peptide (BK) B2 receptor antagonist, FR173657 ((E)‐3‐(6‐acetamido‐3‐pyridyl)‐ N‐[N‐[2,4‐dichloro‐3‐[(2‐methyl‐8‐quinolinyl)oxymethyl]phenyl]‐N‐methylaminocarbonylmethyl] acrylamide) on the plasma exudation in rat carrageenin‐induced pleurisy were investigated.
Plasma exudation induced by intrapleural injection of bradykinin (BK, 3 nmol per rat) into male SD strain rats (SPF, 8 weeks old) were significantly inhibited by oral administration of novel B2 receptor antagonist FR173657 (3–30 mg kg−1, 1 h before BK injection) in a dose‐dependent manner, whereas that induced by histamine was not.
The inhibitory effect of 30 mg kg−1 FR173657 persisted for more than 4 h.
Intrapleural injection of λ‐carrageenin (2% (w/v), 0.1 ml per rat) caused marked plasma exudation and accumulation of exudates from 1 h after carrageenin injection. The maximum plasma exudation response was observed 5 h after carrageenin. The oral administration of FR173657 to rats (30 mg kg−1, 1 h before carrageenin) significantly (by 50–77%) blunted the plasma exudation 1, 3, 5, and 7 h after carrageenin, causing a significant parallel reduction (by 42–57%) in the volume of exudates.
The anti‐inflammatory effect of FR173657 on rat carrageenin‐induced pleurisy was almost equipotent with that of the peptide B2 antagonist Hoe140 (1 mg kg−1, i.v.), a plasma kallikrein inhibitor, soy bean trypsin inhibitor (0.3 mg per rat, intrapleural injection) and bromelain (10 mg kg−1, i.v.).
In pleurisy induced by intrapleural injection of a histamine releaser, compound 48/80, the plasma exudation was observed only within 20 min after the injection. This plasma exudation was not affected by FR173657, although it was completely inhibited by a mixture of pyrilamine (5 mg kg−1, i.v.) and methysergide (3 mg kg−1, i.v.).
These results indicate that FR173657 is an orally active, promising anti‐inflammatory agent for kinin‐dependent inflammation.

British Journal of Pharmacology (1997) 121, 723–730; doi:10.1038/sj.bjp.0701194
Renal α2a/d‐adrenoceptor subtype function: Wistar as compared to spontaneously hypertensive rats
Authors: Intengan H D , Smyth D D 
Published: August 2006

The α2a/d‐adrenoceptor subtype in the rat kidney modulates solute excretion (osmolar clearance). Since the kidney plays a role in chronic regulation of blood pressure, altered renal function may be implicated in the development of hypertension. A second alteration ‐ that of the α2a/d‐adrenoceptor subtype gene ‐ has also been correlated with hypertension in rats and man.
We hypothesized that as a consequence of the altered α2a/d‐adrenoceptor subtype gene previously shown in spontaneously hypertensive (SH) rats, the increase in osmolar clearance following stimulation of the renal α2a/d‐subtype would be attenuated in SH rats as compared to normotensive Wistar rats. In contrast, based on the theory that such functional unresponsiveness of the α2a/d‐subtype would be genetically determined, we further hypothesized that in one kidney‐one clip (1K‐1C) rats, the response to stimulation of the renal α2a/d‐subtype would be intact as compared to the normotensive Wistar 1K‐sham rats.
Male rats were unilaterally nephrectomized under ether anaesthesia. In the 1K‐1C rats, a silver clip (diameter 0.254 mm) was also placed around the left renal artery. On the experimental day, rats were administered pentobarbitone (50.0 mg kg−1, i.p.). The carotid artery and jugular vein were cannulated for blood pressure monitoring and saline infusion. The ureter was catheterized for urine collection. A 31 gauge needle was advanced into the renal artery for infusion of the α2a/d‐selective agonist, guanfacine (vehicle, 1.0, 3.0 and 10.0 nmol kg−1 min−1 in Wistar and SH rats; vehicle and 10.0 nmol kg−1 min−1 in Wistar 1K‐sham and 1K‐1C rats).
In Wistar rats, guanfacine dose‐dependently increased urine flow and sodium excretion. An increase in osmolar clearance but not free water clearance was also observed. However, in SH rats guanfacine failed to alter urine flow, sodium excretion, osmolar and free water clearance. In contrast, in both Wistar 1K‐sham and 1K‐1C rats, guanfacine increased urine flow rate. Again, this response was due solely to an increase in osmolar clearance. At these doses, guanfacine did not alter blood pressure or creatinine clearance during the experiment.
In summary, the ability of the α2a/d‐adrenoceptor subtype to mediate an increase in osmolar clearance was absent in a genetic model of hypertension, the SH rats. This effect was intact in an acquired model of hypertension (1K‐1C rats). This suggested a defective modulation of solute excretion in SH rats which was probably due to alteration of the α2a/d‐subtype gene and not secondary to the elevated blood pressure. The altered α2a/d‐subtype gene and function may therefore play a causal role in the pathogenesis of hypertension.
Evidence that cyclic AMP phosphodiesterase inhibitors suppress interleukin‐2 release from murine splenocytes by interacting with a ‘low‐affinity’ phosphodiesterase 4 conformer
Authors: Souness John E. , Houghton Clare , Sardar Nughat , Withnall Michael T. 
Published: August 2006

We have investigated the suppressive effects of rolipram, RP 73401 (piclamilast) and other structurally diverse inhibitors of cyclic AMP‐specific phosphodiesterase 4 (PDE4) on interleukin (IL)‐2 generation from Balb/c mouse splenocytes exposed to the superantigen, Staphylococcocal enterotoxin‐A (Staph. A). The purpose was to determine whether their potencies are more closely correlated with inhibition of PDE4 from CTLL cells, against which rolipram displays weak potency (low‐affinity PDE4), or displacement of [3H]‐(±)‐rolipram from its high‐affinity binding site (HARBS) in mouse brain cytosol.
RP 73401 (IC50 0.46±0.07 nM, n=4) was a very potent inhibitor of Staph. A‐induced IL‐2 release from Balb/c mouse splenocytes, being >1100 fold more potent than (±)‐rolipram (IC50 540±67 nM, n=3).
A close correlation (r=0.95) was observed between suppression of IL‐2 release by PDE inhibitors and inhibition of PDE4. In contrast, little correlation (r=0.39) was observed between suppression of IL‐2 release and their affinities for the high‐affinity rolipram binding site (HARBS).
RP 73401 only inhibited partially (30–40%) Staph. A‐induced incorporation of [3H]‐thymidine into splenocyte DNA. The PDE3 inhibitor, siguazodan (10 μM), had little or no effect on IL‐2 release or DNA synthesis. This concentration of siguazodan did not enhance the inhibitory action of RP 73401 on IL‐2 release but potentiated its effect on DNA synthesis, increasing potency and efficacy.
Staph. A‐induced DNA synthesis was only partially inhibited by anti‐IL‐2 neutralizing antibody, whereas dexamethazone (100 nM) and cyclosporine A (100 nM) completely blocked the response.
RP 73401 (IC50 6.3±1.9 nM, n=4) was 140 fold more potent than rolipram (IC50 900±300 nM, n=3) in inhibiting Staph. A‐induced [3H]‐thymidine incorporation into splenocyte DNA.
The results implicate a low‐affinity form of PDE4 in the suppression of Staph. A‐induced IL‐2 release from murine splenocytes by PDE inhibitors. The data also indicate that mitogenic factors other than IL‐2, whose elaboration or responses to which are regulated by PDE3 as well as PDE4, contribute to the superantigen‐induced DNA synthesis.

British Journal of Pharmacology (1997) 121, 743–750; doi:10.1038/sj.bjp.0701200
Impairment of endothelium‐dependent but not of endothelium‐independent dilatation in guinea‐pig aorta rings incubated in the presence of elevated glucose
Authors: Dorigo P , Fraccarollo D , Santostasi G , Maragno I 
Published: August 2006

Purine compounds such as ATP and adenosine, respectively endothelium‐dependent and‐independent vasodilators, are largely involved in the control of vascular tone and vascular reactivity to contracting stimuli. We investigated the relaxing activity of ATP and adenosine in guinea‐pig aorta rings exposed for 6 h to elevated glucose concentration (50 mM), in order to mimic hyperglycaemic conditions. Guinea‐pigs were reserpine‐treated (2 mg kg−1, i.p., 48 and 24 h before death).
Rings of aortae incubated in 50 mM glucose, contracted submaximally by 1 μM noradrenaline, lost endothelium‐dependent relaxation in response to acetylcholine (10 nM to 10 μM). Aortae incubated with 50 mM mannose, as a hyperosmotic control, relaxed to acetylcholine normally. Rings of aortae incubated in 50 mM glucose, contracted submaximally by 3 mM 4‐aminopyridine, lost endothelium‐dependent relaxation in response to ATP (30 μM) whereas endothelium‐independent relaxation in response to adenosine (0.3 mM) was well preserved.
The relaxation induced by A23187 or sodium nitroprusside (10 nM to 0.1 μM) did not differ between rings exposed to control (5.5 mM) or elevated glucose (50 mM) and contracted submaximally by 3 mM 4‐aminopyridine.
When incubated with aortic tissue in the presence of elevated glucose, the cyclo‐oxygenase inhibitors, indomethacin (10 μM) and mefenamic acid (30 μM), or the scavenger of superoxide anions, superoxide dismutase (150 u ml−1), prevented the impairment of ATP‐mediated relaxation.
The present results indicate that endothelium‐dependent, receptor‐induced relaxation in response to acetylcholine and ATP is impaired in guinea‐pig aorta rings exposed to elevated glucose. The endothelial dysfunction caused by glucose might be located at a step between receptor activation and intracellular calcium increase, and might be related to an increased metabolism of arachidonic acid coupled to an increased production, or to a reduced inactivation of superoxide anions.
Modulatory role of 1,25 dihydroxyvitamin D3 on pancreatic islet insulin release via the cyclic AMP pathway in the rat
Authors: Bourlon P.‐M. , Faure‐Dussert A. , Billaudel B. 
Published: August 2006

Previous studies have shown that vitamin D3 deficiency impairs the insulin response to glucose via an alteration of signal transduction pathways, such as Ca2+ handling and the phosphoinositide pathway. In the present study the adenylyl cyclase pathway was examined in islets from 3 independent groups: normal rats, 4 weeks‐vitamin D3 deficient rats and one week‐1,25 dihydroxyvitamin D3 (1,25(OH)2D3) treated rats.
We found that the very low rate of insulin release observed in vitamin D3 deficient rats could be restored in vitamin D3 deficient islets only with high concentrations of dioctanoyl‐cyclic AMP (DO‐cyclic AMP), whereas 1,25(OH)2D3 improved the sensitivity of the islets to this exogenous cyclic AMP analogue.
The beneficial effect of 1,25(OH)2D3 observed with or without DO‐cyclic AMP was protein kinase A‐dependent, since the addition of N‐[2‐(p‐bromocinnamylamino) ethyl]‐5‐isoquinolinesulphonamide (H‐89), a specific inhibitor of cyclic AMP‐dependent protein kinases, decreased the insulin release of treated rats back to the level seen in vitamin D3 deficient islets.
The low rate of insulin release could not be consistently related to an alteration in cyclic AMP content of the islets. Indeed, low insulin response to a barium + theophylline stimulus observed in vitamin D3 deficient islets was paradoxically associated with a supranormal cyclic AMP content in the islets.
This paradoxical increase in cyclic AMP observed in these conditions could not be attributed to a lower total phosphodiesterase (PDE) activity, although the portion of Ca2+‐calmodulin‐independent PDE was predominant in islets from vitamin D3 deficient rats.
On the other hand, the higher cyclic AMP content of vitamin D3 deficient islets could be related to an increase in glucagon‐induced cyclic AMP synthesis in relation to the hyperglucagonaemia previously observed in vitamin D3 deficient rats. Since higher concentrations of exogenous glucagon and higher endogenous cyclic AMP concentrations were required in vitro to restore insulin release to normal values, the cyclic AMP‐dependent pathways that usually potentiate insulin secretion appeared to be less efficient in relation to an alteration in the post cyclic AMP effector system.
1,25(OH)2D3 exerted a stimulating effect on insulin release via protein kinase A activation but reduced the supranormal cyclic AMP synthesis, thus exerting a differential modulatory influence on biochemical disturbances in islets induced by vitamin D3 deficiency.

British Journal of Pharmacology (1997) 121, 751–758; doi:10.1038/sj.bjp.0701204
Identification and pharmacological characterization of somatostatin receptors in rat lung
Authors: Schloos Jürgen , Raulf Friedrich , Hoyer Daniel , Bruns Christian 
Published: August 2006

[125I]‐[LTT]SRIF‐28 and [125I]‐SMS 201‐995 were used to identify and characterize somatostatin (SRIF) receptors localized in rat lung tissue. In vitro autoradiography of rat lung tissue sections showed the existence of specific, high affinity binding sites for [125I]‐[LTT]SRIF‐28 without any significant specific binding of the sst2/sst5‐receptor selective ligand [125I]‐SMS 201‐995.
In radioligand binding studies, specific binding of [125I]‐[LTT]SRIF‐28 to membranes of rat lung was linearly related to the concentration of membrane protein used with only a small portion of nonspecific binding. With [125I]‐SMS 201‐995 no specific binding could be observed up to a membrane concentration of 0.1 mg of protein/assay tube.
[125I]‐[LTT]SRIF‐28 bound rapidly to rat lung membranes with an apparent association rate constant (kapp) of 1.8±0.1 h−1 (n=3). The equilibrium of specific binding was reached after an incubation period of approximately 90 min at room temperature and remained constant for the next 3 h. The association rate constant (k1) was calculated to be 3.7×1010 M−1 h−1. The dissociation reaction followed first order kinetics with a dissociation rate constant (k−1)=0.44±0.07 h−1 corresponding to a half‐time of 95±15 min (n=3). From these kinetic experiments an equilibrium dissociation constant (KD) for the binding of [125I]‐[LTT]SRIF‐28 was calculated to be 11.9 pM.
Saturation binding of [125I]‐[LTT]SRIF‐28 revealed an equilibrium dissociation constant (KD) of 50.1 pM (pKD=10.3±0.1; n=3) and a receptor density (Bmax) of 78±3 fmol mg−1 protein. A Hill coefficient not significantly different from 1 indicated saturable binding to a single class of high affinity binding sites.
Specific binding of [125I]‐[LTT]SRIF‐28 to rat lung membranes was inhibited by SRIF‐14, SRIF‐28 and different SRIF analogues. SRIF and different synthetic short chain SRIF analogues exhibited the following rank order of potency: SRIF‐28>SRIF‐14>CGP 23996>>RC 160>BIM 23014>SMS 201‐995>BIM 23056>MK 678.
The binding affinities for SRIF and the various SRIF analogues determined using rat lung tissue were in close correlation to those obtained with Chinese hamster ovary (CHO) cells stably expressing sst1 (r=0.92) and sst4(r=0.95) receptors, respectively.
Reverse transcriptase ‐ polymerase chain reaction (RT‐PCR) showed the predominant expression of mRNA specific for sst4 receptors as well as some weak sst1 mRNA expression.
The findings suggest that sst4 receptor expression is the predominant form of the somatostatin receptors identified in rat lung tissue. In this study we demonstrated for the first time the existence of sst4 receptors in mammalian tissue.
Combined administration of 5‐HT2 and thromboxane A2 antagonists: effects on platelet aggregation and isolated cardiac muscle
Authors: Shaw Linda A , Batey Andrew J , Coker Susan J 
Published: August 2006

To investigate possible mechanisms underlying the ability of combined administration of a 5‐hydroxytryptamine2 (5‐HT2) antagonist and a thromboxane A2 antagonist to reduce reperfusion‐induced arrhythmias, the effects of these drugs alone and in combination on platelet aggregation and on cardiac muscle were determined.
Platelet aggregation was measured in whole blood obtained from anaesthetized rats. Concentrations of 5‐HT (10 μM) and the thromboxane A2 mimetic U46619 (1 μM) which did not cause aggregation themselves, enhanced the responses to ADP (0.1 μM) and to collagen (1 μg ml−1). For example, the response of 1.0±0.5 Ω to ADP alone was increased significantly to 6.4±1.0 Ω by 5‐HT, 15.5±2.8 Ω by U46619, and 17.3±1.3 Ω when U46619, 5‐HT and ADP were added together.
In further experiments blood was obtained from rats which had received either the 5‐HT2 antagonist, ICI 170,809 (1 mg kg−1), or the thromboxane A2 antagonist, ICI 192,605 (1 mg kg−1 min−1), or both in combination. When ADP was used as the primary aggregating agent, the ability of U46619 alone, or together with 5‐HT, to enhance responses was reduced significantly by ICI 192,605 alone and in combination with ICI 170,809. Similar results were obtained with lower doses of ICI 170,809 (0.3 mg kg−1) and ICI 192,605 (0.3 mg kg−1 min−1).
When collagen was used as the primary aggregating agent ICI 170,809 (1 mg kg−1) reduced the response to 5‐HT (5.0±0.8 Ω versus 10.9±1.2 Ω in controls), and ICI 192,605 (1 mg kg−1 min−1) reduced the response to U46619 (6.8±2.5 Ω versus 11.2±2.2 Ω in control). The greatest reduction of platelet aggregation was seen in blood from rats which had received both antagonists, with the response to U46619 plus 5‐HT plus collagen being 2.7± 0.6 Ω compared to 14.2±1.7 Ω in controls. In contrast, there was no significant attenuation of platelet aggregation in blood from rats which had received the lower doses of each antagonist alone. Only the combination of ICI 170,809 (0.3 mg kg−1) and ICI 192,605 (0.3 mg kg−1 min−1) reduced the response to U46619 plus 5‐HT plus collagen (7.6±1.4 Ω versus 15.0±0.5 Ω in controls).
In rat isolated ventricular muscle preparations, ICI 170,809 increased the effective refractory period; e.g. from 39±4 to 86±18 ms, 10 min after adding 30 μM to left papillary muscles. ICI 192,605 did not increase the effective refractory period itself and did not alter the ability of ICI 170,809 to prolong the effective refractory period. In the presence of 100 μM ICI 192,605, ICI 170,809 (30 μM) increased the effective refractory period from 38±7 to 100±30 ms.
These results indicate that the previously observed antiarrhythmic activity of combined administration of the higher doses of ICI 170,809 and ICI 192,605 is unlikely to be due to direct effects on cardiac muscle but could be a consequence of reduced platelet aggregation.
Role of lipocortin‐1 in the anti‐hyperalgesic actions of dexamethasone
Authors: Ferreira S H , Cunha F Q , Lorenzetti B B , Michelin M A , Perretti M , Flower R J , Poole S 
Published: August 2006

The effect of dexamethasone, lipocorton‐12–26 and an antiserum to lipocortin‐12–26 (LCPS1) upon the hyperalgesic activities in rats of carrageenin, bradykinin, tumour necrosis factor α (TNFα), interleukin‐12, interleukin‐6 (IL‐6), interleukin‐8 (IL‐8), prostaglandin Eβ (PGE2) and dopamine were investigated in a model of mechanical hyperalgesia.
Hyperalgesic responses to intraplantar (i.pl.) injections of carrageenin (100 μg), bradykinin (500 ng), TNFα (2.5 pg), IL‐1β (0.5 pg), and IL‐6 (1.0 ng), but not responses to IL‐8 (0.1 ng), PGE2 (100 ng) and dopamine (10 μg), were inhibited by pretreatment with dexamethasone (0.5 mg kg−1, subcutaneously, s.c., or 0.04–5.0 μg/paw).
Inhibition of hyperalgesic responses to injections (i.pl.) of bradykinin (500 ng) and IL‐1β (0.5 pg) by dexamethasone (0.5 mg kg−1, s.c.) was reversed by LCPS1 (0.5 ml kg−1, injected s.c., 24 h and 1 h before hyperalgesic substances) and hyperalgesic responses to injections (i.pl.) of bradykinin (500 ng), TNFα (2.5 pg) and IL‐1β (0.5 pg), but not responses to PGE2 (100 ng), were inhibited by pretreatment with lipocortin‐12–26 (100 μg/paw). Also, lipocortin‐12–26 (30 and 100 μg ml−1) and dexamethasone (10 μg ml−1) inhibited TNFα release by cells of the J774 (murine macrophage‐like) cell‐line stimulated with LPS (3 μg ml−1), and LCPS1 partially reversed the inhibition by dexamethasone. These data are consistent with an important role for endogenous lipocortin‐12–26 in mediating the anti‐hyperalgesic effect of dexamethasone, with inhibiton of TNFα production by lipocortin‐12–26 contributing, in part, to this role.
Although arachidonic acid by itself was not hyperalgesic, the hyperalgesic response to IL‐1β (0.25 pg, i.pl.) was potentiated by arachidonic acid (50 μg) and the potentiated response was inhibited by dexamethasone (50 μg, i.pl.) and lipocortin‐12–26 (100 μg, i.pl.). Also, lipocortin‐12–26 (30 and 100 μg ml−1) inhibited/abolished PGE2 release by J774 cells stimulated with LPS (3 μg ml−1). These data suggest that, in inflammatory hyperalgesia, inhibition of the induction of cyclo‐oxygenase 2 (COX‐2), rather than phospholipase A2, by dexamethasone and lipocortin‐12–26 accounts for the anti‐hyperalgesic effects of these agents.
The above data support the notion that induction of lipocortin by dexamethasone plays a major role in the inhibition by dexamethasone of inflammatory hyperalgesia evoked by carrageenin, bradykinin and the cytokines TNFα, IL‐1β and IL‐6, and provides additional evidence that the biological activity of lipocortin resides within the peptide lipocortin‐12–26. Further, the data suggest that inhibition of lipocortin‐12–26 of eicosanoid production by COX‐2 also contributes to the anti‐hyperalgesic effect of lipocortin‐1.