bluuebunny/crossref_metadata_2025_split huggingface dataset:
Vasorelaxant and antiplatelet activity of 4,7‐dimethyl‐1,2,5‐oxadiazolo[3,4‐d]pyridazine 1,5,6‐trioxide: role of soluble guanylate cyclase, nitric oxide and thiols
Authors: Kots Alexander Ya , Grafov Mikhail A , Khropov Yuri V , Betin Vasily L , Belushkina Natalya N , Busygina Olga G , Yazykova Marina Yu , Ovchinnikov Igor V , Kulikov Alexander S , Makhova Nina N , Medvedeva Natalya A , Bulargina Tamara V , Severina Irina S 
Published: January 2005

Certain heterocyclic N‐oxides are vasodilators and inhibitors of platelet aggregation. The pharmacological activity of the furoxan derivative condensed with pyridazine di‐N‐oxide 4,7‐dimethyl‐1,2,5‐oxadiazolo[3,4‐d]pyridazine 1,5,6‐trioxide (FPTO) and the corresponding furazan (FPDO) was studied.
FPTO reacted with thiols generating nitrite (NO), S‐nitrosoglutathione and hydroxylamine (nitroxyl) and converted oxyHb to metHb. FPDO did not generate detectable amounts of NO‐like species but reacted with thiols and oxyHb.
FPTO and FPDO haem‐dependently stimulated the activity of soluble guanylate cyclase (sGC) and this stimulation was inhibited by 1H‐[1,2,4]oxadiazolo[4,3‐a]quinoxalin‐1‐one (ODQ) and by 0.1 mM dithiothreitol.
FPTO relaxed noradrenaline‐precontracted aortic rings and its concentration‐response curve was biphasic (pIC50=9.03±0.13 and 5.85±0.06). FPDO was significantly less potent vasodilator (pIC50=5.19±0.14). The vasorelaxant activity of FPTO and FPDO was inhibited by ODQ. oxyHb significantly inhibited only FPTO‐dependent relaxation.
FPTO and FPDO were equipotent inhibitors of ADP‐induced platelet aggregation (IC50=0.63±0.15 and 0.49±0.05 μM, respectively). The antiplatelet activity of FPTO (but not FPDO) was partially suppressed by oxyHb. The antiaggregatory effects of FPTO and FPDO were only partially blocked by sGC inhibitors.
FPTO and FPDO (10–20 μM) significantly increased cyclic GMP levels in aortic rings and platelets and this increase was blocked by ODQ.
Thus, FPTO can generate NO and, like FPDO, reacts with thiols and haem. The vasorelaxant activity of FPTO and FPDO is sGC‐dependent and a predominant role is played by NO at FPTO concentrations below 1 μM. On the contrary, inhibition of platelet aggregation is only partially related to sGC activation.

British Journal of Pharmacology (2000) 129, 1163–1177; doi:10.1038/sj.bjp.0703156
Enhanced blood pressure sensitivity to DOCA‐salt treatment in endothelin ETB receptor‐deficient rats
Authors: Matsumura Yasuo , Kuro Toshihiko , Konishi Fumiko , Takaoka Masanori , Gariepy Cheryl E , Yanagisawa Masashi 
Published: January 2005

The role of endothelin ETB receptor‐mediated action in the development and maintenance of deoxycorticosterone acetate (DOCA)‐salt‐induced hypertension was evaluated using the spotting‐lethal (sl) rat which carries a naturally occurring deletion in the ETB receptor gene. Homozygous (sl/sl) rats treated with DOCA‐salt for 1 week exhibited an earlier onset of hypertension than heterozygous (sl/+) and wild‐type (+/+) rats (systolic blood pressure, SBP; 156.7±3.4 versus 128.8±5.3 and 132.9±3.7 mmHg, respectively). Four weeks after the start of DOCA‐salt treatment, homozygous rats developed marked hypertension, with a SBP of 206.0±4.5 mmHg, compared with 184.8±10.7 mmHg in heterozygous and 164.3±4.8 mmHg in wild‐type rats. Cardiovascular hypertrophy and renal dysfunction observed after 4‐weeks treatment with DOCA‐salt were more severe in homozygous rats, compared to wild‐type and heterozygous animals. These evidences support strongly the view that ETB receptor‐mediated actions are a protective factor in the pathogenesis of DOCA‐salt‐induced hypertension.British Journal of Pharmacology (2000) 129, 1060–1062; doi:10.1038/sj.bjp.0703157
β3‐Adrenoceptor regulation and relaxation responses in mouse ileum
Authors: Hutchinson Dana S , Evans Bronwyn A , Summers Roger J 
Published: January 2005

This study examines the relationship between β3a‐ and β3b‐adrenoceptor (AR) mRNA levels, β3‐AR binding and changes in ileum responses in mice treated with the β3‐AR agonist (R,R)‐5‐[2[[2‐(3‐chlorophenyl)‐2‐hydroxyethyl]‐amino]‐propyl]1,3‐benzodioxole‐2,2‐dicarboxylate (CL316243), or the β3‐AR antagonist 3‐(2‐ethylphenoxy)‐1‐[(1S)‐1,2,3,4‐tetrahydronapth‐1‐ylamino]‐2S‐2‐propanol oxalate (SR59230A), or dexamethasone or forskolin.
Levels of β3a‐ and β3b‐AR mRNA and the maximum number of binding sites (Bmax) in ileum were unaffected following CL316243 treatment, although responses to CL316243 were reduced by 50% following 4 and 24 h treatment, indicating another desensitization mechanism not involving changes in receptor expression or number. β3a‐AR mRNA levels were reduced in both brown (BAT) and white adipose tissue (WAT) but β3b‐AR mRNA levels were significantly reduced only in WAT. Levels of β3a‐ and β3b‐mRNA returned towards normal with continued treatment.
SR59230A treatment markedly increased β3‐AR mRNA levels in ileum and BAT but not in WAT. The increase in β3‐AR mRNA levels in ileum was associated with increased Bmax levels in binding analysis and increased responses to CL316243, suggesting these as the cause of sensitization.
Treatment with forskolin (4 h) or dexamethasone (4 h) significantly reduced β3a‐AR mRNA levels in BAT and WAT but did not alter levels in ileum. Responses to CL316243 in ileum were unaffected by either treatment.
In summary, the β3‐AR is differently regulated in adipose tissue and ileum: Treatment with SR59230A increased β3‐AR number, mRNA and responsiveness in ileum, whereas treatment with CL316243 reduced responses without affecting β3‐AR number or mRNA levels.

British Journal of Pharmacology (2000) 129, 1251–1259; doi:10.1038/sj.bjp.0703160
Effect of type‐selective inhibitors on cyclic nucleotide phosphodiesterase activity and insulin secretion in the clonal insulin secreting cell line BRIN‐BD11
Authors: Ahmad M , Abdel‐Wahab Y H A , Tate R , Flatt P R , Pyne N J , Furman B L 
Published: January 2005

The cyclic nucleotide phosphodiesterases (PDEs) present in an insulin secreting cell line, BRIN–BD11, were characterized using calcium/calmodulin, IGF‐1, isoenzyme‐selective PDE inhibitors and RT–PCR.
Calmodulin activated cyclic AMP or cyclic GMP PDE activity in pellet and was 3 fold (P=0.002) more potent in activating cyclic nucleotide hydrolysis in pellet compared with supernatant fractions.
The PDE1/PDE5 inhibitor zaprinast inhibited both cyclic AMP and cyclic GMP PDE activity in both pellet and supernatant fractions of cell homogenates by a maximum of around 25% (IC50 1–5 μM), while rolipram (PDE4 selective) inhibited only cyclic AMP hydrolysis.
The PDE3‐selective inhibitors Org 9935 (0.02–10 μM) and siguazodan (0.1–10 μM) inhibited cyclic AMP PDE activity in the pellet but not the supernatant fractions of cell homogenates, with a maximum inhibition of about 30%. IGF‐1 (2–7.5 ng ml−1) potently augmented this PDE activity.
RT–PCR using specific primers for PDE3B, but not for PDE3A, amplified, from BRIN–BD11 cell total RNA, a 351 base pair product that was >97% homologous with rat adipose tissue PDE3B.
IBMX, Org 9935, siguazodan and rolipram (1–50 μM), but not zaprinast, each augmented glucose‐induced insulin secretion in the presence of 16.7 mM but not 1 mM glucose.
These findings, in a clonal insulin secreting cell line, are consistent with an important role for PDE3B in regulating the pool of cyclic AMP relevant to the modulation of glucose‐induced insulin secretion.

British Journal of Pharmacology (2000) 129, 1228–1234; doi:10.1038/sj.bjp.0703165
Respiratory actions of tachykinins in the nucleus of the solitary tract: effect of neonatal capsaicin pretreatment
Authors: Mazzone Stuart B , Geraghty Dominic P 
Published: January 2005

The respiratory response to microinjection of capsaicin and tachykinin receptor agonists into the commissural nucleus of the solitary tract (cNTS) was investigated in adult, urethane‐anaesthetized rats which had been pretreated with capsaicin (50 mg kg−1 s.c.) or vehicle (10% Tween 80, 10% ethanol in saline) as day 2 neonates.
Microinjection of capsaicin (1 nmol) into the cNTS of vehicle‐pretreated rats, significantly reduced respiratory frequency (59 breaths min−1, preinjection control, 106 breaths min−1) without affecting tidal volume (VT). In capsaicin‐pretreated rats, the capsaicin‐induced bradypnoea was markedly attenuated (minimum frequency, 88 breaths min−1; control, 106 breaths min−1).
In vehicle‐pretreated rats, microinjection of substance P (SP, 33 pmol), neurokinin A (NKA, 33 pmol) and NKB (330 pmol), and the selective NK1 tachykinin receptor agonists, [Sar9,Met(O2)11]‐SP (33 pmol) and septide (10 pmol), increased VT (maxima, 3.60–3.93 ml kg−1) compared with preinjection control (2.82 ml kg−1), without affecting frequency. The selective NK3 agonist senktide (10 pmol) also increased VT (3.93 ml kg−1) which was accompanied by a bradypnoea (−25 breaths min−1). The selective NK2 agonist, [Nle10]‐NKA(4‐10) (330 pmol) increased VT slightly but significantly decreased frequency (−12 breaths min−1). In capsaicin‐pretreated rats, VT responses to SP and [Sar9,Met(O2)11]‐SP were increased whereas the response to septide was abolished. Both the VT and bradypnoeic responses to senktide and [Nle10]‐NKA(4‐10) were significantly enhanced.
These results show that neonatal capsaicin administration markedly reduces the respiratory response to microinjection of capsaicin into the cNTS. The destruction of capsaicin‐sensitive afferents appears to sensitize the NTS to SP, NKB, [Sar9,Met(O2)11]‐SP, senktide and [Nle10]‐NKA(4‐10). Moreover, the loss of septide responsiveness in capsaicin‐pretreated rats, suggests that ‘septide‐sensitive’ NK1 receptors may be located on the central terminals of afferent neurons.

British Journal of Pharmacology (2000) 129, 1132–1139; doi:10.1038/sj.bjp.0703173
The role of adenosine receptors in the action of theophylline on human peripheral blood mononuclear cells from healthy and asthmatic subjects
Authors: Landells L J , Jensen M W , Orr L M , Spina D , O'Connor B J , Page C P 
Published: January 2005

The aim of the present study was to investigate the role of adenosine A2b receptors in the anti‐proliferative action of theophylline in human peripheral blood mononuclear cells (HPBMC) from healthy and asthmatic subjects.
Theophylline significantly inhibited PHA‐induced proliferation of HPBMC from both healthy and asthmatic donors but only at relatively high concentrations at 1 mM (P<0.05). Enprophylline, a drug which also acts as a non‐selective phosphodiesterase (PDE) inhibitor and is a selective A2b receptor antagonist, had no significant effect on proliferation of cells from either group at concentrations up to 10 μM (P>0.05; n=6).
Adenosine deaminase (2 u ml−1), which metabolizes adenosine, had no significant effect on PHA‐induced HPBMC proliferation over a range of concentrations (0–8 μg ml−1) in cells from either healthy or asthmatic subjects.
The adenosine receptor agonists N6‐cyclopentyladenosine (CPA, A1‐selective) and 5′‐N‐ethylcarboxamidoadenosine (NECA, A1/A2) produced a small but significant inhibition of PHA‐induced proliferation of HPBMC from healthy and asthmatic subjects (10 μM, P<0.05; n=6). In contrast, 5′‐N‐ethylcarboxamido‐2‐[4‐(2‐]carboxyethyl)phenethyl]adenosine (CGS21680, A2a‐selective) was without significant effect (P>0.05; n=6).
The adenosine receptor antagonist alloxazine (A2b‐selective) had no significant effect, while 8(3‐chlorostyryl)caffeine,(CSC, A2a‐selective) significantly inhibited PHA‐induced proliferation of HPBMC from both groups (P<0.05; n=6).
Our results suggest that endogenous or exogenous adenosine has little effect on the proliferation of HPBMC obtained from healthy or asthmatic subjects. Thus it would appear that the effect of high concentrations of theophylline is not related to adenosine receptor antagonism.

British Journal of Pharmacology (2000) 129, 1140–1144; doi:10.1038/sj.bjp.0703177
Functional role of muscarinic M2 receptors in α,β‐methylene ATP induced, neurogenic contractions in guinea‐pig ileum
Authors: Sawyer Gregory W , Lambrecht Günter , Ehlert Frederick J 
Published: January 2005

The muscarinic acetylcholine receptors mediating the contractile response elicited to endogenous acetylcholine released by the selective P2X receptor agonist α,β‐methylene ATP (mATP) were investigated in guinea‐pig ileum.
mATP (0.1–30 μM) elicited a concentration‐dependent neurogenic contractile response inhibited by tetrodotoxin (TTX) and antagonized by the non‐selective muscarinic receptor antagonist N‐methylscopolamine (NMS).
The contractile response to mATP was pertussis toxin‐insensitive, irreversibly antagonized by N‐(2‐chloroethyl)‐4‐piperidinyl diphenylacetate (4‐DAMP mustard), and unaffected by the muscarinic M2/M4 receptor selective antagonist AF‐DX 116 (1 μM).
When measured in the presence of histamine and isoproterenol after treatment with 4‐DAMP mustard, mATP elicited a pertussis toxin‐sensitive contractile response potently antagonized by AF‐DX 116.
Collectively, our data suggest that endogenous acetylcholine released by mATP can elicit a direct contractile response through the muscarinic M3 receptor and an indirect contractile response through the muscarinic M2 receptor by antagonizing the relaxant effects of isoproterenol on histamine induced contraction.

British Journal of Pharmacology (2000) 129, 1458–1464; doi:10.1038/sj.bjp.0703180
Pharmacology of human sulphonylurea receptor SUR1 and inward rectifier K+ channel Kir6.2 combination expressed in HEK‐293 cells
Authors: Gopalakrishnan Murali , Molinari Eduardo J , Shieh Char‐Chang , Monteggia Lisa M , Roch Jean‐Marc , Whiteaker Kristi L , Scott Victoria E S , Sullivan James P , Brioni Jorge D 
Published: January 2005

The pharmacological properties of KATP channels generated by stable co‐expression of the sulphonylurea receptor SUR1 and the inwardly rectifying K+ channel Kir6.2 were characterized in HEK‐293 cells.
[3H]‐Glyburide (glibenclamide) bound to transfected cells with a Bmax value of 18.5 pmol mg−1 protein and with a KD value of 0.7 nM. Specific binding was displaced by a series of sulphonylurea analogues with rank order potencies consistent with those observed in pancreatic RINm5F insulinoma and in the brain.
Functional activity of KATP channels was assessed by whole cell patch clamp, cation efflux and membrane potential measurements. Whole cell currents were detected in transfected cells upon depletion of internal ATP or by exposure to 500 μM diazoxide. The currents showed weak inward rectification and were sensitive to inhibition by glyburide (IC50=0.92 nM).
Metabolic inhibition by 2‐deoxyglucose and oligomycin treatment triggered 86Rb+ efflux from transfected cells that was sensitive to inhibition by glyburide (IC50=3.6 nM).
Diazoxide, but not levcromakalim, evoked concentration‐dependent decreases in DiBAC4(3) fluorescence responses with an EC50 value of 14.1 μM which were attenuated by the addition of glyburide. Diazoxide‐evoked responses were inhibited by various sulphonylurea analogues with rank order potencies that correlated well with their binding affinities.
In summary, results from ligand binding and functional assays demonstrate that the pharmacological properties of SUR1 and Kir6.2 channels co‐expressed in HEK‐293 cells resemble those typical of native KATP channels described in pancreatic and neuronal tissues.

British Journal of Pharmacology (2000) 129, 1323–1332; doi:10.1038/sj.bjp.0703181
P2Y2 receptor‐mediated proliferation of C6 glioma cells via activation of Ras/Raf/MEK/MAPK pathway
Authors: Tu Ming‐Tze , Luo Shue‐Fen , Wang Chuan‐Chawn , Chien Chin‐Sung , Chiu Chi‐Tso , Lin Chih‐Chung , Yang Chuen‐Mao 
Published: January 2005

Extracellular purine and pyrimidine nucleotides have been implicated in the regulation of several cellular functions including mitogenesis. In this study, experiments were conducted to characterize the P2Y receptor on C6 glioma cells responsible for stimulating cell proliferation associated with mitogen‐activated protein kinase (MAPK) activation.
UTP and ATP produced a similar effect on [3H]‐thymidine incorporation in a time‐ and concentration‐dependent manner, suggesting the involvement of P2Y2 receptor in mediating proliferation of C6 glioma cells.
In response to UTP, both p42 and p44 MAPK were activated in a time‐ and concentration‐dependent manner using Western blot analysis with an anti‐phospho‐p42/p44 MAPK antibody. The phosphorylation reached maximal levels after 5 min and declining by 30 min.
Pretreatment with pertussis toxin (PTX) did not change these responses to UTP. Both DNA synthesis and phosphorylation of MAPK in response to UTP were attenuated by tyrosine kinase inhibitors, genistein and herbimycin A, protein kinase C (PKC) inhibitors, staurosporine and GF109203X, and removal of Ca2+ by addition of BAPTA/AM plus EGTA.
UTP‐induced [3H]‐thymidine incorporation and p42/p44 MAPK phosphorylation was completely inhibited by PD98059 (an inhibitor of MEK1/2). Furthermore, we showed that overexpression of dominant negative mutants of Ras (RasN17) and Raf (Raf‐301) completely suppressed MEK1/2 and p42/p44 MAPK activation induced by ATP and UTP.
These results conclude that the mitogenic effect of UTP is mediated through a P2Y2 receptor that involves the activation of Ras/Raf/MEK/MAPK pathway. UTP‐mediated MAPK activation was modulated by Ca2+, PKC, and tyrosine kinase associated with cell proliferation in cultured C6 glioma cells.

British Journal of Pharmacology (2000) 129, 1481–1489; doi:10.1038/sj.bjp.0703182
Characterization of human recombinant α2A‐adrenoceptors expressed in Chinese hamster lung cells using extracellular acidification rate changes
Authors: MacLennan S J , Reynen P H , Martin R S , Eglen R M , Martin G R 
Published: January 2005

Human α2A‐adrenoceptors heterologously expressed in Chinese hamster lung (CHL) fibroblasts have been characterized pharmacologically using a cytosensor microphysiometer to measure ligand‐induced extracellular acidification rate changes.
In untransfected CHL cells, noradrenaline had no effect at concentrations up to 100 μM. In α2A‐adrenoceptor transfected cells the rank order of agonist potency was A‐54741 (mean pEC50=8.96)>dexmedetomidine (8.88)>UK‐14304 (8.42)>B‐HT 920 (7.05)>noradrenaline (6.92). A‐54741, UK‐14304 and noradrenaline had the same maximum response while dexmedetomidine and B‐HT 920 behaved as partial agonists.
The selective α2‐adrenoceptor ligand rauwolscine antagonized acidification rate changes with an affinity independent of the agonist used; the affinity (mean pKB) against noradrenaline was 8.43.
The selective α1‐adrenoceptor ligands prazosin and doxazosin (each 3 μM) had no effect on noradrenaline responses.
Acidification rate changes induced by each agonist were abolished by pre‐treatment of cells with pertussis toxin.
These data suggest that agonist‐induced acidification rate responses in CHL cells transfected with the human α2A‐adrenoceptor are mediated exclusively by the recombinant protein, via pertussis toxin sensitive Gi/o proteins.

British Journal of Pharmacology (2000) 129, 1333–1338; doi:10.1038/sj.bjp.0703183
The P2Y1 receptor closes the N‐type Ca2+ channel in neurones, with both adenosine triphosphates and diphosphates as potent agonists
Authors: Filippov Alexander K , Brown David A , Barnard Eric A 
Published: January 2005

The rat P2Y1 nucleotide receptor, the P2Y subtype abundant in the brain, was heterologously expressed in rat superior cervical ganglion neurones by micro‐injection of the receptor cRNA or cDNA. ADP inhibited the N‐type Ca2+ current by 64%, with EC50 8.2 nM, an action blocked competitively by the P2Y1 receptor antagonist adenosine 3′, 5′‐bis‐phosphate (Ki 0.7 μM). 2‐Methylthio‐ADP inhibited the Ca2+ current likewise, but with EC50 0.57 nM, giving the highest potency reported therewith for P2Y1. Significantly, ATP and 2‐methylthio‐ATP were also agonists, the latter again at a very high potency (EC50 2.5 nM). We propose that this neuronal receptor, when present in brain at a high density as at synapses, can respond to very low concentrations of ATP and ADP as agonists, and that this would result in inhibition of N‐type Ca2+ currents and hence can reduce transmitter release or increase neuronal excitability.British Journal of Pharmacology (2000) 129, 1063–1066; doi:10.1038/sj.bjp.0703185
Effects of protein tyrosine kinase inhibitors on voltage‐operated calcium channel currents in vascular smooth muscle cells and pp60c‐src kinase activity
Authors: Wijetunge S , Lymn J S , Hughes A D 
Published: January 2005

Tyrosine kinases have been proposed as regulators of voltage‐operated calcium channels. The effects of a range of structurally different inhibitors of protein tyrosine kinases (PTK) were examined on voltage‐operated calcium channel currents (IBa) and pp60c‐src kinase (c‐src) activity in vitro.
IBa was measured in single myocytes isolated from rabbit ear artery by conventional whole cell voltage‐clamp techniques. The activity of purified human c‐src was measured in vitro using a non‐radioactive assay.
Bath application of tyrphostin‐23 and genistein (non‐selective PTK inhibitors), bistyrphostin (a receptor‐PTK‐selective inhibitor) and PP1 (a src family‐selective inhibitor) inhibited IBa in a concentration‐dependent manner over a range of test membrane potentials. Intracellular application of peptide‐A, a peptide inhibitor of c‐src also inhibited currents. Inhibitor potency series against IBa was PP1 > genistein > tyrphostin 23 > bistyrphostin.
Tyrphostin‐23, genistein, PP1, and peptide‐A shifted the steady‐state inactivation curves in a hyperpolarized direction without altering their slope. The inhibitors had no significant effects on IBa activation calculated from current‐voltage relationships.
The agents inhibited c‐src activity in a concentration‐dependent manner. The order of potency was PP1 > genistein > peptide‐A > tyrphostin‐23 > bistyrphostin. The IC50 for inhibition of c‐src activity was similar to the IC50 for inhibition of IBa in all cases.
Western blot analysis with a specific antibody to c‐src showed the presence of this cytoplasmic tyrosine kinase in rabbit ear artery cells.
A range of structurally dissimilar inhibitors of PTKs inhibit IBa and c‐src activity with similar potency. These data provide further evidence implicating endogenous c‐src in the modulation of L‐type calcium channels in vascular smooth muscle cells.

British Journal of Pharmacology (2000) 129, 1347–1354; doi:10.1038/sj.bjp.0703186