bluuebunny/crossref_metadata_2025_split huggingface dataset:
Purinoceptor subtypes mediating contraction and relaxation of marmoset urinary bladder smooth muscle
Authors: McMurray Gordon , Dass Narinder , Brading Alison F. 
Published: January 2005

The effects of adenosine triphosphate (ATP), adenosine diphosphate (ADP), α,β‐methylene‐ATP (α,β‐MeATP) and 2‐methylthio‐ATP (2‐MeSATP) on longitudinally orientated smooth muscle strips from marmoset urinary bladder were investigated by use of standard organ bath techniques.
After being mounted in superfusion organ baths, 66.7% (n=249) of marmoset detrusor smooth muscle strips developed spontaneous tone, 48.2% of all strips examined developed tone equivalent to greater than 0.1 g mg−1 of tissue and were subsequently utilized in the present investigation.
On exposure to ATP, muscle strips exhibited a biphasic response, a rapid and transient contraction followed by a more prolonged relaxation. Both responses were found to be concentration‐dependent. ADP and 2‐MeSATP elicited a similar response (contraction followed by relaxation), whereas application of α,β‐MeATP only produced a contraction. The potency order for each effect was α,β‐MeATP>>2‐MeSATPATP>ADP (contractile response) and ATP=2‐MeSATPADP>>α,β‐MeATP (relaxational response).
Desensitization with α,β‐MeATP (10 μM) abolished the contractile phase of the response to ATP, but had no effect on the level of relaxation evoked by this agonist. On the other hand, the G‐protein inactivator, GDPβS (100 μM) abolished only the relaxation response to ATP. Suramin (general P2 antagonist, 100 μM) shifted both the contractile and relaxation ATP concentration‐response curves to the right, whereas cibacron blue (P2Y antagonist, 10 μM) only antagonized the relaxation response to ATP. In contrast, the adenosine receptor antagonist, 8‐phenyltheophylline (10 μM), had no effect on the relaxation response curve to ATP.
Incubation with tetrodotoxin (TTX, 3 μM) or depolarization of the muscle strip with 40 mM K+ Krebs failed to abolish the relaxation to ATP. In addition, neither Nω‐nitro‐L‐arginine (L‐NOARG, 10 μM) nor methylene blue (10 μM) had any effect on the relaxation response curve. However, tos‐phe‐chloromethylketone (TPCK, 3 μM), an inhibitor of cyclicAMP‐dependent protein kinase A (PKA), significantly (P<0.01) shifted the curve for the ATP‐induced relaxation to the right.
It is proposed that marmoset detrusor smooth muscle contains two receptors for ATP, a classical P2X‐type receptor mediating smooth muscle contraction, and a P2Y (G‐protein linked) receptor mediating smooth muscle relaxation. The results also indicate that the ATP‐evoked relaxation may occur through the activation of cyclicAMP‐dependent PKA.

British Journal of Pharmacology (1998) 123, 1579–1586; doi:10.1038/sj.bjp.0701774
The effects of nifedipine and other calcium antagonists on the glibenclamide‐sensitive K+ currents in smooth muscle cells from pig urethra
Authors: Teramoto Noriyoshi , Brading Alison F. 
Published: January 2005

The effects of nifedipine on both levcromakalim‐induced membrane currents and unitary currents in pig proximal urethra were investigated by use of patch‐clamp techniques (conventional whole‐cell configuration and cell‐attached patches).
Nifedipine had a voltage‐dependent inhibitory effect on voltage‐dependent Ba2+ currents at −50 mV (Ki=30.6 nM).
In current‐clamp mode, subsequent application of higher concentrations of nifedipine (30 μM) caused a significant depolarization even after the membrane potential had been hyperpolarized to approximately −82 mV by application of 100 μM levcromakalim.
The 100 μM levcromakalim‐induced inward current (symmetrical 140 mM K+ conditions, −50 mV) was inhibited by additional application of three different types of Ca antagonists (nifedipine, verapamil and diltiazem, all at 100 μM). In contrast, Bay K 8644 (1 μM) possessed no activating effect on the amplitude of this glibenclamide‐sensitive current.
When 100 μM nifedipine was included in the pipette solution during conventional whole‐cell recording at −50 mV, application of levcromakalim (100 μM) caused a significant inward membrane current which was suppressed by 5 μM glibenclamide. On the other hand, inclusion of 5 μM glibenclamide in the pipette solution prevented levcromakalim from inducing an inward membrane current.
The levcromakalim‐induced K+ channel openings in cell‐attached configuration were suppressed by subsequent application of 5 μM glibenclamide but not of 100 μM nifedipine.
These results suggest that in pig proximal urethra, nifedipine inhibits the glibenclamide‐sensitive 43 pS K+ channel activity mainly through extracellular blocking actions on the K+ channel itself.

British Journal of Pharmacology (1998) 123, 1601–1608; doi:10.1038/sj.bjp.0701777
Involvement of calcitonin gene‐related peptide (CGRP) receptors in insulin‐induced vasodilatation in mesenteric resistance blood vessels of rats
Authors: Mimaki Yuichi , Kawasaki Hiromu , Okazaki Masatoshi , Nakatsuma Akira , Araki Hiroaki , Gomita Yutaka 
Published: January 2005

The vascular effect of insulin in the mesenteric resistance blood vessel and the role of calcitonin gene‐related peptide (CGRP)‐receptor in insulin‐induced vascular responsiveness were investigated in rats.
The mesenteric vascular beds isolated from Wistar rats were perfused with Krebs solution, and perfusion pressure was measured with a pressure transducer. In preparations contracted by perfusion with Krebs solution containing methoxamine in the presence of guanethidine, the perfusion of insulin (from 0.1 to 3000 nM) caused a concentration‐dependent decrease in perfusion pressure due to vasodilatation. The pD2 value and maximum relaxation (%) were 6.94±0.22 and 43.9±5.2, respectively.
This vasodilator response to insulin was unaffected by 100 nM propranolol (β‐adrenoceptor antagonist) plus 100 nM atropine (muscarinic cholinoceptor antagonist), 100 μM L‐NG‐nitroarginine (nitric oxide synthase inhibitor), 1 μM ouabain (Na+‐K+ ATPase inhibitor), or 1 μM glibenclamide (ATP sensitive K+‐channel inhibitor).
In preparations without endothelium, perfusion of insulin produced a marked vasodilatation. The pD2 value and maximum relaxation (%) were 7.62±0.21 and 81.0±4.6, respectively, significantly greater than in preparations with intact endothelium.
The vasodilator responses to insulin in the preparations without endothelium were significantly inhibited by CGRP[8–37], a CGRP receptor antagonist, whereas pretreatment with capsaisin, a toxin for CGRP‐containing nerves, did not affect insulin‐induced vasodilatation.
These results suggest that insulin induces non‐adrenergic, non‐cholinergic and endothelium‐independent vasodilatation, which is partially mediated by CGRP receptors.

British Journal of Pharmacology (1998) 123, 1684–1690; doi:10.1038/sj.bjp.0701779
Endothelin receptors mediating contraction of rat and human pulmonary resistance arteries: effect of chronic hypoxia in the rat
Authors: McCulloch Kirsty M. , Docherty Cheryl , MacLean Margaret R. 
Published: January 2005

We examined the endothelin (ET) receptors mediating contractions to ET‐1, ET‐3 and sarafotoxin S6c (SX6c) in rat pulmonary resistance arteries by use of peptide and non‐peptide ET receptor antagonists. Changes induced by pulmonary hypertension were examined in the chronically hypoxic rat. The effect of the mixed ETA/ETB receptor antagonist SB 209670 on endothelin‐mediated contraction was also examined in human pulmonary resistance arteries.
In rat vessels, the order of potency for the endothelin agonists was SX6c=ET‐3>ET‐1 (pEC50 values in control rats: 9.12±0.10, 8.76±0.14 and 8.12±0.04, respectively). Maximum contractions induced by ET‐3 and ET‐1 were increased in vessels from chronically hypoxic rats.
The ETA receptor antagonist FR 139317 (1 μM) had no effect on the potency of ET‐1 in any vessel studied but abolished the increased response to ET‐1 in the chronically hypoxic vessels. The ETA receptor antagonist BMS 182874 (1 μM) increased the potency of ET‐1 in control rat vessels without effecting potency in the pulmonary hypertensive rat vessels.
Bosentan (non‐peptide mixed ETA/ETB receptor antagonist) increased the potency of ET‐1 in control rat vessels but was without effect in the pulmonary hypertensive rat vessels. Bosentan (1 μM) inhibited responses to SX6c in control and chronically hypoxic rat vessels with pKb values of 5.84 and 6.11, respectively. The ETB receptor antagonist BQ‐788 (1 μM) did not inhibit responses to ET‐1 in any vessel tested but did inhibit responses to both SX6c and ET‐3 (pKb values in control and chronically hypoxic rat vessels respectively: SX6c 7.15 and 7.22; ET‐3: 6.68 and 6.89). BQ‐788 (1 μM) added with BMS 182874 (10 μM) did not inhibit responses to ET‐1 in control vessels but caused a significant inhibition of responses to ET‐1 in chronically hypoxic preparations.
SB 209670 inhibited responses to ET‐1 in both control and chronically hypoxic vessels with pKb values of 7.36 and 7.39, respectively. SB 209670 (0.1 and 1 μM) virtually abolished responses to ET‐1 in the human pulmonary resistance artery.
In conclusion, in rat pulmonary resistance arteries, vasoconstrictions induced by ET‐1, SX6c and ET‐3 are mediated predominantly by activation of an ETB–like receptor. However, lack of effect of some antagonists on ET‐1 induced vasoconstriction suggests that ET‐1 stimulates an atypical ETB receptor. The increase in potency of ET‐1 in the presence of some antagonists suggests the presence of an inhibitory ETA‐like receptor. The influence of this is reduced, or absent, in the chronically hypoxic rats. Increased responses to ET‐1 are observed in the chronically hypoxic rat and may be mediated by increased activation of ETA receptors. SB 209670 is unique in its potency against responses to ET‐1 in both control and chronically hypoxic rats, as well as human, isolated pulmonary resistance arteries.

British Journal of Pharmacology (1998) 123, 1621–1630; doi:10.1038/sj.bjp.0701785
Differential mechanism for the cell surface sorting and agonist‐promoted internalization of the α1B‐adrenoceptor
Authors: Hirasawa Akira , Awaji Takeo , Sugawara Tatsuo , Tsujimoto Aiko , Tsujimoto Gozoh 
Published: January 2005

α1B‐adrenoceptors are localized at a steady state in the plasma membrane in untreated cells, and internalize to intracellular vesicles when exposed to agonist. Flow cytometry analysis with an anti‐N‐terminus‐antibody (1B‐N1‐C, (Hirasawa et al., 1996)) facilitated the quantification of cell surface α1B‐adrenoceptor. Also, the cellular distribution of α1B‐adrenoceptors was visually monitored by immunocytochemical confocal microscopy.
Utilizing this combined approach, we have examined the molecular mechanism for cellular trafficking of α1B‐adrenoceptors, including the process of sorting of the synthesized receptor protein to the cell surface, and the agonist‐induced internalization. The two processes were separately examined by using α1B‐adrenoceptor inducible DDT1MF‐2 cells for the sorting process and CHO cells stably expressing α1B‐adrenoceptors for the agonist‐promoted internalization.
We examined the effects of cytochalasin D and mycalolide B (actin depolymerization agents), demecolcine (a microtubule disrupting agent), brefeldin A (an inhibitor of vesicular transport and Golgi function), bafilomycin A1 (a specific inhibitor of the vacuolar proton pump) or hyperosmotic sucrose treatment (that may inhibit clathrin‐mediated endocytosis) on these processes.
We found that the agonist‐promoted internalization was blocked by cytochalasin D and mycalolide B, while the cell surface sorting process was specifically blocked by brefeldin A, indicating that the two processes involve different components of the cellular endocytic machinery.
The experimental approach as exemplified in this study would provide a valuable system to study further the molecular mechanism(s) of cellular trafficking of G protein‐coupled receptors.
Nitric oxide regulation of monkey myometrial contractility
Authors: Kuenzli Karri A , Buxton Iain L O , Bradley Michael E 
Published: January 2005

We evaluated the effect of the nitric oxide (NO) donor CysNO (S‐nitroso‐L‐cysteine) and endogenous NO upon spontaneous contractility in non‐pregnant cynomolgus monkeys. We also assessed the role of intracellular guanosine 3′,5′‐cyclic monophosphate ([cyclic GMP]i) as a second messenger for NO in monkey uterine smooth muscle.
CysNO reduced spontaneous contractility by 84% (P<0.05) at maximal concentrations, and significantly elevated [cyclic GMP]i (P<0.05). However, increases in [cyclic GMP]i were not required for CysNO‐induced relaxations; CysNO inhibited contractile activity despite the complete inhibition of guanylyl cyclase by methylene blue or LY83,583.
Analogues of cyclic GMP had no significant effect upon spontaneous contractile activity. L‐arginine produced a 62% reduction in spontaneous activity (P<0.05) while D‐arginine had no effect. The competitive nitric oxide synthase (NOS) inhibitor Nω‐nitro‐L‐arginine (L‐NOARG) not only blocked L‐arginine‐induced relaxations, but also significantly increased spontaneous contractile activity when added alone (P<0.05); the inactive D‐enantiomer of NOARG had no such effect.
While both endogenous NO and the NO donor CysNO relax monkey myometrium, this effect is not causally related to CysNO‐induced elevations in [cyclic GMP]i. The failure of cyclic GMP analogues to alter monkey uterine smooth muscle tension also argues against a role for [cyclic GMP]i in the regulation of uterine contractility. Not only do these findings argue for the existence of a functionally‐relevant NOS in the monkey uterus, but increases in contractile activity seen in the presence of NOS inhibitors suggest a role for NO in the moment‐to‐moment regulation of contractile activity in this organ.
Carbachol stimulation of gastric acid secretion and its effects on the parietal cell
Authors: Sandvik Arne K , Mårvik Ronald , Dimaline Rod , Waldum Helge L 
Published: January 2005

The acid secretagogue effect of gastrin is mainly mediated by the release of enterochromaffin‐like (ECL) cell histamine, but the mechanism of muscarinic stimulation of acid secretion remains unclear. The results of studying aminopyrine uptake in isolated parietal cells, and histamine release in isolated ECL cells suggest that muscarinic agents may act both directly on the parietal cell and indirectly via histamine release from ECL cells.
We examined parietal and ECL cell responses to the muscarinic agent carbamylcholine (carbachol) in conscious rats and in rat isolated vascularly perfused stomachs.
Intravenous carbachol stimulated acid secretion in conscious gastric fistula rats and increased H+K+ ATPase mRNA abundance, indicating activation of parietal cells. In these experiments there was no increase in portal venous histamine, or in oxyntic mucosal histidine decarboxylase (HDC) enzyme activity and HDC mRNA abundance.
In rat isolated stomachs stimulated with carbachol in the dose range 10 nM–1 mM only the 1 μM concentration increased venous histamine significantly.
We concluded that the muscarinic agent carbachol stimulates acid secretion and H+K+ ATPase mRNA in vivo by a direct effect on the parietal cell, that does not depend on the release of ECL cell histamine.
Discovery of novel melanocortin4 receptor selective MSH analogues
Authors: Schiöth Helgi B , Mutulis Felikss , Muceniece Ruta , Prusis Peteris , Wikberg Jarl E S 
Published: January 2005

We synthesized a novel series of cyclic melanocyte stimulating hormone (MSH) analogues and tested their binding properties on cells transiently expressing the human melanocortin1 (MC1), MC3, MC4 and MC5 receptors.
We discovered that compounds with 26 membered rings of [Cys4,D‐Nal7,Cys11]α‐MSH(4–11) displayed specific MC4 receptor selectivity. The preference order of the different MC receptor subtypes for the novel [Cys4D‐Nal7Cys11]α‐MSH(4–11) analogues are distinct from all other known MSH analogues, particularly as they bind the MC4 receptor with high and the MC1 receptor with low relative affinities.
HS964 and HS014 have 12 and 17 fold MC4/MC3 receptor selectivity, respectively, which is much higher than for the previously described cyclic lactam and [Cys4,Cys10]α‐MSH analogues SHU9119 and HS9510.
HS964 is the first substance showing higher affinity for the MC5 receptor than the MC1 receptor.
HS014, which was the most potent and selective MC4 receptor ligand (Ki 3.2 nM, which is ∼300 fold higher affinity than for α‐MSH), was also demonstrated to antagonize α‐MSH stimulation of cyclic AMP in MC4 receptor transfected cells.
We found that a compound with a 29 membered ring of [Cys3,Nle10,D‐Nal7,Cys11]α‐MSH(3–11) (HS010) had the highest affinity for the MC3 receptor.
This is the first study to describe ligands that are truly MC4 selective and a ligand having a high affinity for the MC3 receptor. The novel compounds may be of use in clarifying the physiological roles of the MC3, MC4 and MC5 receptors.
Effects of adrenomedullin and calcitonin gene‐related peptide on contractions of the rat aorta and porcine coronary artery
Authors: Yoshimoto Ryo , Mitsui‐Saito Minori , Ozaki Hiroshi , Karaki Hideaki 
Published: January 2005

Effects of adrenomedullin and α‐calcitonin gene‐related peptide (CGRP) on the contractions and cytosolic Ca2+ concentrations ([Ca2+]i) of the rat aorta and porcine coronary artery were investigated. Characteristics of the receptors mediating the effects of adrenomedullin and α‐CGRP were also investigated.
Adrenomedullin and α‐CGRP caused a concentration‐dependent relaxation in the rat aorta contracted with noradrenaline. The IC50 values for adrenomedullin and α‐CGRP were 2.4 nM and 4.0 nM, respectively. The relaxant effects of these peptides were abolished by removal of the endothelium and significantly attenuated by an inhibitor of nitric oxide synthase, NG‐monomethyl‐L‐arginine (L‐NMMA, 100 μM), but not by a cyclo‐oxygenase inhibitor, indomethacin (10 μM).
Adrenomedullin and α‐CGRP increased the endothelial [Ca2+]i in the rat aorta with endothelium, whereas they did not change [Ca2+]i in the smooth muscle.
An antagonist of the CGRP1 receptor, CGRP (8–37), antagonized the relaxant effects of α‐CGRP and the β‐isoform of CGRP (β‐CGRP) but not those of adrenomedullin in the rat aorta.
In the porcine coronary artery contracted with U46619, adrenomedullin and α‐CGRP caused a concentration‐dependent relaxation with an IC50 of 27.6 and 4.1 nM, respectively. Removal of the endothelium altered neither the IC50 values nor the maximal relaxations induced by adrenomedullin or α‐CGRP. When the artery was contracted with high K+ solution (72.7 mM), these peptides caused a small relaxation.
Adrenomedullin and α‐CGRP increased cyclic AMP content and decreased the smooth muscle [Ca2+]i in the porcine coronary artery.
CGRP (8–37) significantly antagonized the relaxant effects of adrenomedullin and α‐CGRP in the porcine coronary artery. However, it had little effect on the relaxations induced by the β‐isoform of CGRP (β‐CGRP).
These results suggest that in the rat aorta, adrenomedullin and α‐CGRP increase the endothelial [Ca2+]i, activate nitric oxide synthase and release nitric oxide, without a direct inhibitory action on smooth muscle. In the porcine coronary artery, in contrast, adrenomedullin and α‐CGRP directly act on smooth muscle, increase cyclic AMP content, decrease the smooth muscle [Ca2+]i and inhibit contraction. The rat aortic endothelium seems to express the CGRP receptor which is sensitive to α‐CGRP, β‐CGRP and CGRP (8–37) and the adrenomedullin specific receptor. The porcine coronary smooth muscle, in contrast, seems to express two types of CGRP receptor; one of which is sensitive to α‐CGRP, CGRP (8–37) and adrenomedullin and the other is sensitive only to β‐CGRP.

British Journal of Pharmacology (1998) 123, 1645–1654; doi:10.1038/sj.bjp.0701805
Effects of calcium and potassium supplements on arterial tone in vitro in spontaneously hypertensive rats
Authors: Tolvanen Jari‐Petteri , Mäkynen Heikki , Wu Xiumin , Hutri‐Kähönen Nina , Rsukoaho Heikki , Karjala Kirsi , Pörsti Ilkka 
Published: January 2005

Calcium and potassium intakes inversely correlate with blood pressure in experimental hypertension. Therefore, we examined the effects of calcium and potassium supplements alone and in combination on arterial tone in spontaneously hypertensive rats (SHR). Wistar‐Kyoto (WKY) rats served as normotensive controls. Calcium and potassium contents in the control diet were both 1%, while those in supplemented chows were 3% and 3.5%, respectively. The sodium content of all diets was moderately elevated to 1.1%.
After 12 weeks of the study systolic blood pressures in SHR on high calcium and on high potassium diets were markedly lower (about 53 and 58 mmHg, respectively) than in hypertensive controls, while combined supplementation of these cations reduced blood pressure even further (about 69 mmHg).
Responses of mesenteric arterial rings in vitro were examined at the end of the study. Both high calcium and high potassium diets improved the impaired relaxation to acetylcholine (ACh) in SHR, while the combination of these supplements completely normalized this response. Cyclo‐oxygenase inhibition by diclofenac augmented the relaxation to ACh in hypertensive controls but not in the other groups. Nevertheless, enhanced endothelium‐mediated dilatation was still observed in the presence of diclofenac and the nitric oxide synthase inhibitor NG‐nitro‐L‐arginine methyl ester (L‐NAME) in all supplemented groups. Interestingly, additional blockade of Ca2+‐activated K+ channels by tetraethylammonium abolished the improved relaxation to ACh in SHR on high calcium and on high potassium, but distinct responses were still observed in WKY rats and SHR on the combined supplement.
When hyperpolarization of smooth muscle was prevented by precontraction of the preparations with 50 mM KCl, only marginal differences were observed in the diclofenac and L‐NAME‐resistant relaxations to ACh between the study groups. Finally, endothelium‐independent vasorelaxations of noradrenaline‐precontracted rings to nitroprusside, isoprenaline and cromakalim were comparably augmented by all supplements.
In conclusion, the vascular mechanisms underlying the antihypertensive effect of high calcium and high potassium diets during moderately elevated sodium intake in SHR may involve enhanced arterial hyperpolarization, increased smooth muscle sensitivity to nitric oxide and decreased production of vasoconstrictor prostanoids. The administration of these cations in combination was more effective than either of them alone in reducing blood pressure and restoring arterial tone.