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Predicate | Object |
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rdf:type | |
lifeskim:mentions | |
pubmed:issue |
3
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pubmed:dateCreated |
1980-1-28
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pubmed:abstractText |
For direct identification of alpha-adrenoceptors in a membrane fraction of the rabbit heart the potent alpha-adrenoceptor antagonist [3H]-dihydroergocryptine ([3H]-DHE) was used. 1. The binding of [3H]-DHE was saturable with 80 fmol of [3H]-DHE bound/mg protein and of high affinity with an equilibrium dissociation constant (KD) of 11.5 nM. Binding of [3H]-DHE (6 nM) was rapid (t 1/2 = 2 min) and readily reversible. From the ratio of the rate constants for forward (K1 = 1.97 X 10(7) M-1 min-1) and reverse (K2 = 0.206 min-1) reactions a KD-value of 10 nM was calculated, which is in good agreement with that obtained by equilibrium studies. 2. Adrenergic agonists compete for [3H]-DHE binding in an order to potency: (-)adrenaline greater than (-)phenyleprine greater than (-)isoprenaline and adrenergic antagonists in the order: phentolamine greater than yohimbine greater than (-)propranolol. Binding is stereospecific as indicated by the greater potency of (-)adrenaline than (+/-)adrenaline in displacing [3H]-DHE from the binding sites. 3. For comparison the binding of the potent beta-adrenoceptor antagonist (-)[3H]-dihydroalprenolol ((-)[3H]-DHA) was measured in the same membrane fraction. The number and affinity of beta-adrenoceptors amounted to 115 fmol of (-)[3H]-DHA bound/mg protein at saturation and KD = 7.9 nM. Adrenergic agonists compete for (-)[3H]-DHA binding in an order of potency: (-)isoprenaline greater than (-)adrenaline greater than (-)phenylephrine; and adrenergic antagonists in the order: (-)prapranolol greater than phentolamine. 4. It is concluded that in a membrane fraction of the rabbit heart there exist binding sites for [3H]-DHE which have characteristics indistinguishable from alpha-adrenoceptors. Thus the present results are in agreement with previously reported data on the existence of cardiac alpha-adrenoceptors in the rabbit heart (Schümann et al., 1974; Endoh et al., 1976b).
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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/Adrenergic alpha-Agonists,
http://linkedlifedata.com/resource/pubmed/chemical/Adrenergic alpha-Antagonists,
http://linkedlifedata.com/resource/pubmed/chemical/Dihydroergotoxine,
http://linkedlifedata.com/resource/pubmed/chemical/Receptors, Adrenergic,
http://linkedlifedata.com/resource/pubmed/chemical/Receptors, Adrenergic, beta
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pubmed:status |
MEDLINE
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pubmed:month |
Sep
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pubmed:issn |
0028-1298
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pubmed:author | |
pubmed:issnType |
Print
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pubmed:volume |
308
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pubmed:owner |
NLM
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pubmed:authorsComplete |
Y
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pubmed:pagination |
191-8
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pubmed:dateRevised |
2006-11-15
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pubmed:meshHeading |
pubmed-meshheading:41191-Adrenergic alpha-Agonists,
pubmed-meshheading:41191-Adrenergic alpha-Antagonists,
pubmed-meshheading:41191-Animals,
pubmed-meshheading:41191-Binding Sites,
pubmed-meshheading:41191-Dihydroergotoxine,
pubmed-meshheading:41191-Female,
pubmed-meshheading:41191-Heart,
pubmed-meshheading:41191-Kinetics,
pubmed-meshheading:41191-Male,
pubmed-meshheading:41191-Membranes,
pubmed-meshheading:41191-Rabbits,
pubmed-meshheading:41191-Receptors, Adrenergic,
pubmed-meshheading:41191-Receptors, Adrenergic, beta,
pubmed-meshheading:41191-Time Factors
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pubmed:year |
1979
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pubmed:articleTitle |
Demonstration of alpha-adrenoceptors in the rabbit heart by [3H]-dihydroergocryptine binding.
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pubmed:publicationType |
Journal Article,
In Vitro
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