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Predicate | Object |
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rdf:type | |
lifeskim:mentions | |
pubmed:issue |
1-2
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pubmed:dateCreated |
1989-7-7
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pubmed:abstractText |
The nature of the receptors that mediate the relaxation of smooth muscle by field stimulation, (-)-noradrenaline and (-)-adrenaline was investigated in calf tracheal smooth muscle. The relation between relaxation, stimulation of the adenylate cyclase and density of beta-adrenoceptor subtypes was studied with the help of antagonists of beta 1- and beta 2-adrenoceptors. The question of the existence of catecholamine-containing nerves was also investigated. (1) Nerves with varicosities exhibiting catecholaminergic fluorescence were observed between bundles of smooth muscle cells. (2) Consistent with the existence of adrenergic nerves (-)-noradrenaline was also found. The content of (-)-noradrenaline (1 microgram.g-1 w.w.) was the same in smooth muscle strips from the sublaryngeal region and from the region close to the bifurcation of the calf trachea. (-)-Adrenaline was not detected. (3) Smooth muscle relaxation by low (-)-noradrenaline concentration (0.6-2 nmol/l) was mediated through beta 1-adrenoceptors. Low concentrations of (-)-adrenaline (0.06-1 nmol/l) relaxed through beta 2-adrenoceptors. High concentrations of (-)-noradrenaline and (-)-adrenaline also caused relaxation through beta 2- and beta 1-adrenoceptors respectively. (4) Field stimulation caused relaxation which was half maximal at 0.2-0.8 Hz. Blockade of beta 1-adrenoceptors strongly attenuated the relaxant response to field stimulation and shifted the frequency-relaxation curves to 4 times higher frequencies. These results are consistent with a beta 1-adrenoceptor-mediated relaxation caused by (-)-noradrenaline released from sympathetic nerve endings at low stimulation frequencies. (5) Blockade of beta 2-adrenoceptors failed to reduce smooth muscle relaxation caused by field stimulation at low stimulation frequencies (0.1-1 Hz). However, after beta 1-adrenoceptor blockade, additional blockade of beta 2-adrenoceptors reduced the relaxant effects observed at high frequencies (2-400 Hz). The results suggest that high concentrations of endogenous (-)-noradrenaline cause relaxation through beta 2-adrenoceptors. (6) Binding experiments with 3H-(-)-bupranolol and 3H-ICI 118,551 revealed between 10,000 and 20,000 beta-adrenoceptors per smooth muscle cell of which 3/4 were beta 2 and 1/4 beta 1. The equilibrium dissociation constant of (-)-adrenaline for both beta 1- and beta 2-adrenoceptors and of (-)-noradrenaline for beta 1-adrenoceptors was 1 mumol/l. The affinity of (-)-noradrenaline for beta 2-adrenoceptors was 10 to 20 times lower than for beta 1-adrenoceptors.(ABSTRACT TRUNCATED AT 250 WORDS)
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pubmed:language |
eng
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pubmed:journal | |
pubmed:citationSubset |
IM
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pubmed:chemical |
http://linkedlifedata.com/resource/pubmed/chemical/Adenylate Cyclase,
http://linkedlifedata.com/resource/pubmed/chemical/Adrenergic beta-Antagonists,
http://linkedlifedata.com/resource/pubmed/chemical/CGP 20712A,
http://linkedlifedata.com/resource/pubmed/chemical/Catecholamines,
http://linkedlifedata.com/resource/pubmed/chemical/Epinephrine,
http://linkedlifedata.com/resource/pubmed/chemical/ICI 118551,
http://linkedlifedata.com/resource/pubmed/chemical/Imidazoles,
http://linkedlifedata.com/resource/pubmed/chemical/Norepinephrine,
http://linkedlifedata.com/resource/pubmed/chemical/Propanolamines,
http://linkedlifedata.com/resource/pubmed/chemical/Receptors, Adrenergic, beta
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pubmed:status |
MEDLINE
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pubmed:issn |
0028-1298
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pubmed:author | |
pubmed:issnType |
Print
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pubmed:volume |
339
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pubmed:owner |
NLM
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pubmed:authorsComplete |
Y
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pubmed:pagination |
85-98
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pubmed:dateRevised |
2006-11-15
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pubmed:meshHeading |
pubmed-meshheading:2566929-Adenylate Cyclase,
pubmed-meshheading:2566929-Adrenergic beta-Antagonists,
pubmed-meshheading:2566929-Animals,
pubmed-meshheading:2566929-Catecholamines,
pubmed-meshheading:2566929-Cattle,
pubmed-meshheading:2566929-Electric Stimulation,
pubmed-meshheading:2566929-Epinephrine,
pubmed-meshheading:2566929-Imidazoles,
pubmed-meshheading:2566929-Muscle, Smooth,
pubmed-meshheading:2566929-Muscle Relaxation,
pubmed-meshheading:2566929-Neurons,
pubmed-meshheading:2566929-Norepinephrine,
pubmed-meshheading:2566929-Propanolamines,
pubmed-meshheading:2566929-Receptors, Adrenergic, beta,
pubmed-meshheading:2566929-Trachea
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pubmed:articleTitle |
Neuronally released (-)-noradrenaline relaxes smooth muscle of calf trachea mainly through beta 1-adrenoceptors: comparison with (-)-adrenaline and relation to adenylate cyclase stimulation.
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pubmed:affiliation |
Department of Clinical Physiology, University of Düsseldorf, Federal Republic of Germany.
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pubmed:publicationType |
Journal Article,
Comparative Study,
In Vitro,
Research Support, Non-U.S. Gov't
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