Binding of [3H]dihydroazapetine to alpha adrenoreceptor related proteins from rat vas deferens

R. R. Ruffolo, J. W. Fowble, Duane Miller, P. N. Patil

Research output: Contribution to journalArticle

25 Citations (Scopus)

Abstract

The potent alpha adrenoreceptor blocking agent, azapetine, has been catalytically reduced with tritium gas to form [3H]dihydroazapetine. [3H]Dihydroazapetine retains significant ability to block alpha adrenoreceptors and has been used as a ligand to study the receptor in a subcellular fraction containing membrane fragments from rat vas deferens. Specific binding of [3H]dihydroazapetine rapidly reaches equilibrium and is also reversible and saturable with a dissociation constant similar to that determined pharmacologically. The binding capacity is approximately 40 pmol/mg of protein. All alpha adrenergic blockers tested were able to inhibit specific binding. High concentrations of alprenolol, atropine, or chlorpheniramine had no effect. In addition, all alpha adrenergic agonists of the imidazoline class inhibit binding in low concentrations, whereas soterenol or carbamylcholine did not. There is good correlation (r = 0.84) between blockade or stimulation of the receptor in intact tissues and inhibition of binding of [3H]dihydroazapetine to the subcellular fraction. These findings suggest that the fraction contains alpha adrenoreceptor related proteins. Alpha adrenergic agonists structurally related to norepinephrine caused a stereoselective increase in binding in favor of the (-) isomer, possibly reflecting an allosteric interaction at a different binding site on the receptor protein. The possibility of two different modes of binding for structurally dissimilar agonists is suggested.

Original languageEnglish (US)
Pages (from-to)2730-2734
Number of pages5
JournalProceedings of the National Academy of Sciences of the United States of America
Volume73
Issue number8
DOIs
StatePublished - Jan 1 1976

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Vas Deferens
Adrenergic alpha-Agonists
Subcellular Fractions
Proteins
Alprenolol
Chlorpheniramine
Imidazolines
Adrenergic alpha-Antagonists
Tritium
Carbachol
Atropine
Norepinephrine
Gases
Binding Sites
Ligands
Membranes
dihydroazapetine

All Science Journal Classification (ASJC) codes

  • General

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Binding of [3H]dihydroazapetine to alpha adrenoreceptor related proteins from rat vas deferens. / Ruffolo, R. R.; Fowble, J. W.; Miller, Duane; Patil, P. N.

In: Proceedings of the National Academy of Sciences of the United States of America, Vol. 73, No. 8, 01.01.1976, p. 2730-2734.

Research output: Contribution to journalArticle

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