bluuebunny/crossref_metadata_2025_split huggingface dataset:
Comparative studies of the angiogenic activity of vasoactive intestinal peptide, endothelins‐1 and −3 and angiotensin II in a rat sponge model
Authors: Hu De‐En , Hiley C. Robin , Fan Tai‐Ping D. 
Published: July 2012

The angiogenic activity of four vasoactive peptides with a range of vasodilator and vasoconstrictor properties, i.e. vasoactive intestinal peptide (VIP), endothelin‐1, endothelin‐3 and angiotensin II, were investigated in a rat sponge model. Neovascularization was assessed by the 133Xe clearance technique and confirmed by histological studies.
Daily doses of the vasodilator peptide, VIP (1000 pmol), caused intense neovascularization, but a lower dose (10 pmol) produced no apparent effect. However, the lower dose of VIP, when given with a subthreshold dose of interleukin‐1α (0.3 pmol), produced an angiogenic response similar to that seen with the higher dose of VIP. The neovascular response induced by co‐administration of VIP and interleukin‐1α was inhibited by simultaneous administration of 100 pmol VIP (10–28), a specific VIP receptor antagonist.
In contrast, daily doses of 10, 100 or 1000 pmol endothelin‐3 (a mixed vasoconstrictor and vasodilator with more marked vasodilator activity) or of 100 or 1000 pmol endothelin‐1 (also with mixed activity but with much more pronounced vasoconstrictor response) produced no apparent effect on sponge‐induced angiogenesis.
The vasoconstrictor peptide, angiotensin II, in daily doses of 1000 pmol, caused an intense neovascularization like VIP but lower doses of angiotensin II (10 or 100 pmol) produced no apparent effect. The lowest dose of angiotensin II (10 pmol) when administered with the subthreshold dose of interleukin‐1α (0.3 pmol) had no effect on the basal neovascular response in the sponges. The angiotensin II‐induced neovascular response was inhibited by co‐administration of 100 nmol of the specific AT1 receptor antagonist, losartan, but not by the AT2 receptor antagonist, PD 123319.
These data show that VIP and angiotensin II possess angiogenic activity. However, endothelin‐1 and endothelin‐3 had no activity at the doses used. Thus the angiogenic response is not related to local vasoconstriction or vasodilatation in the sponges. The blockade of VIP‐ and angiotensin II‐induced angiogenesis at the receptor level suggests that receptor modulation could provide a strategy for the management of angiogenic diseases.
The longitudinal muscle of rat ileum as a sensitive monoreceptor assay for bradykinin B1 receptors
Authors: Meini Stefania , Lecci Alessandro , Maggi Carlo Alberto 
Published: July 2012

Various bradykinin derivatives, acting preferentially at B1 or B2 receptors, were tested in the isolated longitudinal smooth muscle of rat ileum. Experiments were carried out in the presence of chlorpheniramine and atropine (both 1 μm), guanethidine and indomethacin (both 3 μm) and of the peptidase inhibitors (captopril, bestatin and thiorphan, all 1 μm).
The rank order of potency was (pD2 values±s.e.mean, n = 5 in parentheses, at 5 h from set‐up): [des‐ Arg9]‐BK (8.27±0.11)≥ [des‐Arg10]‐kallidin (7.67±0.24) > bradykinin (6.69±0.25). The B2 receptor selective agonist, [Hyp3, Tyr(Me)8]‐BK, was approximately 10 fold less active than bradykinin. Contractile responses to all agonists increased with time. The maximal response to the B1 receptor agonist, [desArg9]‐BK at 5 h (94±2%) was significantly (P<0.05) greater than that measured at 2 h (74±2%).
The B2 receptor antagonist, D‐Arg[Hyp3, Thi5, D‐Tic7, Oic8]‐BK (Hoe 140, 0.1 μm) did not affect responses to the B1 receptor agonist [des‐Arg9‐BK (0.1 nM‐1 μm) nor those to the B2 receptor agonist, [Hyp3, Tyr(Me)8]‐BK (1 nM‐10 μm). In control experiments performed in the longitudinal smooth muscle of guinea‐pig ileum and rat isolated urinary bladder as bioassays for B2 receptors, the B2 receptor antagonist Hoe 140 (0.1 μm) antagonized bradykinin‐induced contractions.
In the rat isolated ileum the B1 receptor antagonist, D‐Arg[Hyp3, Thi5, D‐Tic7, Oic8, des‐Arg9]‐BK ([des‐Arg10]‐Hoe 140, 0.3–10 μm) competitively antagonized contractile responses to [des‐Arg9]‐BK with an estimated pKB of 6.74±0.08 (Schild plot slope with confidence limits 1.22, (0.70‐1.73) n = 13). In control experiments in the guinea‐pig isolated ileum and rat isolated urinary bladder, [des‐Arg10]‐Hoe 140 (1–10 μm) did not inhibit B2 receptor‐mediated contractile responses.
The putative B1 receptor antagonist, [Leu8, des‐Arg9]‐BK, behaved as a partial agonist when responses were determined 2 h from set‐up (pD2 6.43±0.21, n = 5; Emax 30% of that evoked by [des‐Arg9‐BK); at 5 h from set‐up it behaved as a full agonist (pD2 7.48±0.12, n = 5; Emax 90% of that evoked by [des‐ Arg9]‐BK). At this time the response to [Leu8, des‐Arg9]‐BK was antagonized in a concentration‐dependent manner by [des‐Arg10]‐Hoe 140, which at 1 μm and 10 μm, produced dose‐ratios of 6.33±3.66 (n = 4) and 103±40 (n = 4).
In view of the rank order of potency of agonists, the antagonist activity by [des‐Arg10]‐Hoe 140 and the lack of antagonist activity of Hoe 140, we conclude that the longitudinal smooth muscle of rat ileum, after histamine, acetylcholine, noradrenaline, and prostanoid production blockade, is a sensitive monoreceptor assay for studying the pharmacology of bradykinin B1 receptors. Further the preparation can also be used as a sensitive bioassay to identify partial agonist activity of B1 receptor antagonists such as [Leu8, desArg9]‐BK.
KW‐3902, a selective high affinity antagonist for adenosine A1 receptors
Authors: Nonakay Hiromi , Ichimura Michio , Takeda Masami , Kanda Tomoyuki , Shimada Junichi , Suzuki Fumio , Kase Hiroshi 
Published: July 2012

We demonstrate that 8‐(noradamantan‐3‐yl)‐1,3‐dipropylxanthine (KW‐3902) is a very potent and selective adenosine A1 receptor antagonist, assessed by radioligand binding and cyclic AMP response in cells.
In rat forebrain adenosine A1 receptors labelled with [3H]‐cyclohexyladenosine (CHA), KW‐3902 had a Ki value of 0.19 nM, whereas it showed a Ki value of 170 nM in rat striatal A2A receptors labelled with [3H]‐2‐[p‐(2‐carboxyethyl)‐phenethylamino]‐5′‐N‐ethylcarboxamidoadenosine (CGS21680), indicating 890 fold A1 receptor selectivity versus the A2A receptor. KW‐3902 at 10 μm showed no effect on recombinant rat A3 receptors expressed on CHO cells.
Saturation studies with [3H]‐KW‐3902 revealed that it bound with high affinity (Kd = 77 pM) and limited capacity (Bmax = 470 fmol mg−1 of protein) to a single class of recognition sites. A high positive correlation was observed between the pharmacological profile of adenosine ligands inhibiting the binding of [3H]‐KW‐3902 and that of [3H]‐CHA.
KW‐3902 showed potent A1 antagonism against the inhibition of forskolin‐induced cyclic AMP accumulation in DDT1 MF‐2 cells by the Arselective agonist, cyclopentyladenosine with a dissociation constant (KB value) of 0.34 nM. KW‐3902 antagonized 5′‐N‐ethylcarboxamidoadenosine‐elicited cyclic AMP accumulation via A2B receptors with a KB value of 52 nM.
KW‐3902 exhibited marked species‐dependent differences in the binding affinities. The highest affinity was for the rat A1 receptor (Ki = 0.19 nM) and these values for guinea‐pig and dog A1 receptors were 1.3 and 10 nM, respectively.
P2‐purinoceptors mediating spasm of the isolated uterus of the non‐pregnant guinea‐pig
Authors: Piper Angela S. , Hollingsworth Michael 
Published: July 2012

The isolated uterus of the non‐pregnant guinea‐pig has been suggested to contain P1‐, and possibly P2‐purinoceptors mediating spasm. The presence of P1‐purinoceptors has been confirmed and these receptors have been further characterized.
In the presence of the adenosine uptake inhibitor, S‐(4‐nitrobenzyl)‐6‐thioinosine (NBTI, 300 nM) and a pA100 concentration of the P1‐purinoceptor antagonist 8‐sulphophenyltheophylline (140 μm), the potency order of agonists as spasmogens was: 2 methylthio ATP»αβ methylene ATP = UTP = ATP» βγ methylene ATP. This order is not consistent with any single recognised P2‐purinoceptor subtype.
Indomethacin (1 μm) treatment abolished responses to 2 methylthio ATP, αβ methylene ATP and UTP, while spasm to ATP was significantly inhibited. When the endometrial and circular smooth muscle cell layers were removed, spasmogenic responses to ATP, 2 methylthio ATP, αβ methylene ATP and UTP were significantly reduced.
2 methylthio ATP was able to cause desensitization to itself, but not to UTP, indicating that these agonists act at different receptor sites.
The P2‐purinoceptor antagonist, suramin antagonized 2 methylthio ATP with a pA2 of 5.9±0.3. Suramin was also an antagonist of ATP and UTP. In the case of ATP, the antagonism was not dependent on suramin concentration, while for UTP the interaction appeared to be non‐equilibrium. Pyridoxalphosphate‐6‐azophenyl‐2′,4′‐disulphonic acid (PPADS, 10 μm) had no effect on spasm to ATP, UTP or 2 methythio ATP.
In the presence of indomethacin, responses to ATP were unaffected by 8‐sulphophenyltheophylline (140 μm) or by suramin (100 μm), but PPADS (10 μm) antagonized ATP.
These results suggest that the isolated uterus of the non‐pregnant guinea‐pig contains a mixture of P2‐purinoceptors. P2U‐ (or UTP‐selective pyrimidinoceptors) and P2Y‐purinoceptors appear to be present, probably mainly located on the endometrial or circular smooth muscle layer. Activation of these receptors leads to spasm via increases in prostanoid generation. There appears also to be a third class of non‐P2X‐, non P2Y‐purinoceptor present, at which ATP is an agonist and PPADS is an antagonist, located on the longitudinal smooth muscle, activation of which causes spasm independent of changes in prostanoids.
Translocation of lipocortin (annexin) 1 to the membrane of U937 cells induced by phorbol ester, but not by dexamethasone
Authors: Kang Sin Ae , Cho Young Ju , Moon Hee‐Bom , Na Doe Sun 
Published: July 2012

Induction of lipocortin 1 secretion by dexamethasone has been demonstrated, although the secretory mechanism is still unknown. We have studied the effects of 12‐tetradecanoyl phorbol 13‐acetate (TPA) and/or dexamethasone on the expression, translocation, and secretion of lipocortin 1 in U937 cells.
The expression of lipocortin 1 and its mRNA increased during TPA‐induced differentiation of U937 cells to a maximum of 1.9 fold and 8.2 fold, respectively, after 48 h. Both the protein and the mRNA levels decreased after 48 h.
TPA caused the translocation of lipocortin 1 from the cytosol to the membrane of U937 cells in a time‐dependent manner, as determined by Western blot analysis. The translocation was concurrent with the differentiation of the cells. After 48 h of TPA treatment, 82.6 ± 6.5% of lipocortin 1 was present in the membrane fraction compared to 41.6 ± 1.7% in untreated cells.
The amount of lipocortin 1 that was externally bound (associated) with the membrane increased to 3.2 fold as the cytosol to membrane translocation of lipocortin 1 increased.
Dexamethasone decreased the externally bound lipocortin 1, but had no effect on the cytosol to membrane translocation.
This offers a model system with which the function and the secretion mechanism of lipocortin 1 can be studied. Our data is consistent with the hypothesis that the secretory mechanism is through an unknown pathway, involving the translocation of lipocortin 1 from the cytosol to the internal membranes, and then, its secretion to the external membrane.
Effect of lacidipine on fatty and proliferative lesions induced in hypercholesterolaemic rabbits
Authors: Soma M.R. , Donetti E. , Seregni R. , Barberi L. , Fumagalli R. , Paoletti R. , Catapano A.L. 
Published: July 2012

The in vivo antiatherogenic activity of the calcium antagonist, lacidipine, was investigated in two different types of atherosclerotic lesions (proliferative and fatty lesions) induced in rabbits.
The proliferative lesion was obtained by positioning a hollow silastic collar around one carotid artery, while aortic fatty lesions were induced by cholesterol feeding. Cholesterol (1%) and lacidipine (1,3, and 10 mg kg−1) were given daily mixed with standard diet for 8 weeks to White New Zealand rabbits. The intimal hyperplasia (proliferative lesion) was induced 6 weeks after dietary and drug treatment started.
The neointimal formation was determined by measuring cross sectional thickness of intimal (I) and medial (M) tissue of fixed arteries. In untreated animals (n=5), 14 days after collar positioning an intimal hyperplasia was clearly detectable: the arteries with no collar (sham) showed an I/M tissue ratio of 0.03±0.02, whereas in the carotid with collar the ratio was 0.62±0.12. In lacidipine‐treated animals a significant and dose‐dependent effect on proliferative lesions at all three doses tested, was observed. I/M ratios were 0.47±0.02, 0.40±0.09, 0.32±0.02 for doses 1, 3, and 10 mg kg−1 day−1, respectively (P<0.05).
The fatty lesion extent was significantly reduced by lacidipine at the 10 mg kg−1 day−1 dose, although a trend was also observed with lower dosage.
These results suggest a direct antiatherosclerotic effect of lacidipine, independent of modulation of risk factors such as hypercholesterolaemia and/or hypertension. Furthermore, the proliferative lesions are apparently more sensitive to lacidipine than are lipid‐rich lesions.
Paracrine renal endothelin system in rats with liver cirrhosis
Authors: Hocher Berthold , Zart Rüdiger , Diekmann Fritz , Rohmeiss Peter , Distler Armin , Neumayer Hans H. , Bauer Christian , Gross Peter 
Published: July 2012

Liver cirrhosis was induced in rats by CCl4 administration. We analysed the expression of endothelin receptor subtypes in the renal cortex and medulla using Scatchard analysis and receptor autoradiography, and measured plasma as well as renal‐tissue endothelin‐1 concentrations using a specific radioimmunoassay. Furthermore, we analysed the effects of the non‐selective (A/B) endothelin receptor antagonist, bosentan (6 and 100 mg kg−1 day−1) on mean arterial blood pressure, water and sodium excretion and glomerular filtration rate.
Our study revealed an overexpression of the endothelin B receptor (ETB) in the renal medulla of rats with liver cirrhosis (Cir: 2775 ± 299 fmol mg−1; Con:1695 ± 255 fmol mg−1; n = 8; means ± s.d., P < 0.01), whereas the density of ETB in the cortex and the endothelin A receptor (ETA) in the cortex and medulla were similar in both cirrhotic and control rats. Receptor autoradiography showed that the upregulation of medullary ETB in cirrhotic rats was due to an upregulation of ETB in the inner medullary collecting duct cells.
The tissue endothelin‐1 concentrations were increased in the renal medulla of cirrhotic rats (Cir:271 ± 68 pg g−1wet wt.; Con: 153 ± 36 pg g−1 wet wt., n = 8; means ± s.d., P < 0.01).
The glomerular filtration rate was slightly decreased in cirrhotic rats but not altered after bosentan treatment in either cirrhotic or control rats. Bosentan decreased sodium excretion to a similar extent in both cirrhotic and control rats, whereas water excretion was significantly reduced by both dosages of bosentan in cirrhotic rats only (Cir + vehicle: 12.5 ± 0.62 ml day−1, Cir + 6 mg kg−1 day−1 bosentan: 8.6 ± 1.0 ml day−1; Cir + 100 mg kg−1 day−1 bosentan:7.4 ± 0.6 ml day−1; n = 10; means ± s.e.mean).
We therefore suggest that the upregulation of the medullary ETB in cirrhotic rats is involved in the regulation of water excretion in rats with CCl4‐induced liver cirrhosis.
Rhythmic relaxations of active tension in the rabbit large arteries induced by a combination of cyclopiazonic acid and Bay K 8644
Authors: Omote Masayuki , Mizusawa Hideo 
Published: July 2012

We previously demonstrated that cyclopiazonic acid (CPA), an inhibitor of Ca2+‐ATPase in the sarcoplasmic reticulum, induced rhythmic relaxations of active tension in the endothelium‐denuded small arteries of the mesentery and the ear of the rabbit, but that this agent failed to induce rhythmic responses in the endothelium‐denuded rabbit femoral artery.
In the present study, an attempt was made to induce rhythmic relaxations of active tension in the endothelium‐denuded rabbit femoral artery and the thoracic aorta, both of which were suspended in organ chambers for isometric tension recordings, by using CPA plus Bay K 8644, an L‐type Ca2+ channel agonist, to induce an excessive increase in cytosolic Ca2+.
CPA or Bay K 8644 alone failed to produce rhythmic relaxations in the femoral artery that had been contracted with phenylephrine. In contrast, rhythmic responses were induced by the sequential treatment of the femoral artery with CPA and Bay K 8644.
The rhythmic relaxations of active tension in the femoral artery induced by CPA plus Bay K 8644 were inhibited by charybdotoxin and by iberiotoxin, both of which are antagonists of the Ca2+‐activated K+ channel, but not by glibenclamide, a blocker of the ATP‐sensitive K+ channel.
The endothelium‐denuded rabbit aorta also exhibited rhythmic responses by the sequential addition of CPA and Bay K 8644. These responses were sensitive to charybdotoxin.
These findings indicate that, like small arteries, the large femoral and aortic arteries of the rabbit are also capable of displaying rhythmic relaxations of active tension; these relaxations may be in part attributed to the activation of the Ca2+‐activated K+ channel as a result of the Ca2+ overload caused by CPA and Bay K 8644.
Rat striatal muscarinic receptors coupled to the inhibition of adenylyl cyclase activity: potent block by the selective m4 ligand muscarinic toxin 3 (MT3)
Authors: Olianas Maria C. , Adem Abdu , Karlsson Evert , Onali Pierluigi 
Published: July 2012

In rat striatal membranes, muscarinic toxin 3 (MT3), a selective ligand of the cloned m4 receptor subtype, antagonized the acetylcholine (ACh) inhibition of forskolin‐and dopamine D1 receptor‐stimulated adenylyl cyclase activities with pA2 values of 8.09 and 8.15, respectively.
In radioligand binding experiments, MT3 increased the Ki but did not change the Bmax value of [3H]‐ N‐methylscopolamine (3H]‐NMS) binding to rat striatal muscarinic receptors. The toxin displaced the major portion of the [3H]‐NMS binding sites with a Ki of 8.0 nM.
In rat myocardium, MT3 antagonized the ACh inhibition of adenylyl cyclase with a Ki value of 860 nM.
In rat cerebral cortical membranes prelabelled with [3H]‐myo‐inositol, MT3 counteracted the methacholine stimulation of [3H]‐inositol phosphates formation with a Ki value of 113 nM.
The present study shows that MT3 is a potent antagonist of the striatal muscarinic receptors coupled to inhibition of adenylyl cyclase activity. This finding provides strong evidence for the classification of these receptors as pharmacologically equivalent to the m4 gene product (M4). On the other hand, the weaker potencies of MT3 in antagonizing the muscarinic responses in cerebral cortex and in the heart are consistent with the reported lower affinities of the toxin for the cloned ml and m2 receptor subtypes, respectively.
Effects of the non‐peptide, non‐selective endothelin antagonist, bosentan, on regional haemodynamic responses to NG‐monomethyl‐L‐arginine in conscious rats
Authors: Gardiner S.M. , Kemp P.A. , March J.E. , Bennett T. 
Published: July 2012

Male, Long Evans rats (350–450 g) were chronically instrumented to allow monitoring of mean arterial blood pressure, heart rate and changes in renal, mesenteric and hindquarters haemodynamics. In the first experiment, animals (n = 8) were given a bolus i.v. injection of the nitric oxide synthase inhibitor, NG‐monomethyl‐L‐arginine hydrochloride (L‐NMMA; 30 mg kg−1) on four consecutive days. Fifteen min prior to L‐NMMA administration on the fourth day, the endothelin, ETA‐, ETB‐receptor antagonist, bosentan, was injected (30 mg kg−1, i.v.). Relative to the response on the third day, bosentan caused 33±4%, 24±3%, 14±3%, and 18±5% inhibition of the pressor, and renal, mesenteric and hindquarters vasoconstrictor effects of L‐NMMA, respectively.
In the second experiment, bosentan was given 15 min before L‐NMMA in a group of rats (n = 6) which had not received L‐NMMA previously. Relative to the responses to L‐NMMA on the first day in the previous experiment, bosentan caused a 30%, 24%, 18% and 27% inhibition of the pressor, and renal, mesenteric and hindquarters vasoconstrictor effects of L‐NMMA, respectively.
The results indicate a significant contribution from endothelin to the haemodynamic effects of L‐NMMA in conscious rats. However, since our previous studies have shown the renin‐angiotensin and sympathoadrenal systems are not involved, it is likely that the major component of the cardiovascular response to L‐NMMA in conscious rats is due to loss of vasodilator action of endothelial nitric oxide.
Inhibition of glycolysis and enhanced mechanical function of working rat hearts as a result of adenosine A1 receptor stimulation during reperfusion following ischaemia
Authors: Finegan Barry A. , Lopaschuk Gary D. , Gandhi Manoj , Clanachan Alexander S. 
Published: July 2012

This study examined effects of adenosine and selective adenosine A1 and A2 receptor agonists on glucose metabolism in rat isolated working hearts perfused under aerobic conditions and during reperfusion after 35 min of global no‐flow ischaemia.
Hearts were perfused with a modified Krebs‐Henseleit buffer containing 1.25 mM Ca2+, 11 mM glucose, 1.2 mM palmitate and insulin (100 μu ml−1), and paced at 280 beats min−1. Rates of glycolysis and glucose oxidation were measured from the quantitative production of 3H2O and 14CO2, respectively, from [5‐3H/U‐14C]‐glucose.
Under aerobic conditions, adenosine (100 μm) and the adenosine A1 receptor agonist, N6‐cyclohexyladenosine (CHA, 0.05 μm), inhibited glycolysis but had no effect on either glucose oxidation or mechanical function (as assessed by heart rate systolic pressure product). The improved coupling of glycolysis to glucose oxidation reduced the calculated rate of proton production from glucose metabolism. The adenosine A1 receptor antagonist, 8‐cyclopentyl‐1,3‐dipropylxanthine (DPCPX 0.3 μm) did not alter glycolysis or glucose oxidation per se but completely antagonized the adenosine‐ and CHA‐induced inhibition of glycolysis and proton production.
During aerobic reperfusion following ischaemia, CHA (0.05 μm) again inhibited glycolysis and proton production from glucose metabolism and had no effect on glucose oxidation. CHA also significantly enhanced the recovery of mechanical function. In contrast, the selective adenosine A2a receptor agonist, CGS‐21680 (1.0 μm), exerted no metabolic or mechanical effects. Similar profiles of action were seen if these agonists were present during ischaemia and throughout reperfusion or when they were present only during reperfusion.
DPCPX (0.3 μm), added at reperfusion, antagonized the CHA‐induced improvement in mechanical function. It also significantly depressed the recovery of mechanical function per se during reperfusion. Both the metabolic and mechanical effects of adenosine (100 μm) were antagonized by the nonselective A1/A2 antagonist, 8‐sulphophenyltheophylline (100 μm).
These data demonstrate that inhibition of glycolysis and improved recovery of mechanical function during reperfusion of rat isolated hearts are mediated by an adenosine A1 receptor mechanism. Improved coupling of glycolysis and glucose oxidation during reperfusion may contribute to the enhanced recovery of mechanical function by decreasing proton production from glucose metabolism and the potential for intracellular Ca2+ accumulation, which if not corrected leads to mechanical dysfunction of the post‐ischaemic myocardium.