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The importance of choice of agonist in studies designed to predict β 2:β 1 adrenoceptor selectivity of antagonists from pA2 values on guinea-pig trachea and atria

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Summary

  1. 1.

    pA2 values have been obtained for propranolol, butoxamine, H35/25 and atenolol on guinea-pig isolated trachea and atria (rate) using noradrenaline (β 1-selective), isoprenaline (non-selective) and fenoterol (β 2-selective) as agonists.

  2. 2.

    pA2 values varied with the agonist used on trachea but not on atria and, therefore, trachea: atria selectivity values varied with the agonist used.

  3. 3.

    It is suggested that the best estimate of the selectivity of an antagonist between β 2- and β 1-adrenoceptors is obtained by comparing its pA2 value obtained on trachea using a β 2-selective agonist with that obtained on atria using a β 1-selective agonist. The reasons for this are discussed.

  4. 4.

    The quantitative values for β 2:β 1 selectivity obtained using the above pA2 values were butoxamine 17.0, H35/25 13.5, propranolol 2.75 and atenolol 0.036, i.e. butoxamine and H35/25 were β 2-selective, propranolol was non-selective and atenolol was β 1-selective.

  5. 5.

    The results support the hypotheses that guinea-pig trachea contains a mixture of β 1- and β 2-adrenoceptors and that guinea-pig atria contain only β 1-adrenoceptors.

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Authors and Affiliations

  1. Pharmacology Section, Department of Physiology, University of Queensland, St. Lucia, 4067, Brisbane, Queensland, Australia

    Stella R. O'Donnell & Janet C. Wanstall

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  1. Stella R. O'Donnell
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  2. Janet C. Wanstall
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This study was supported by the National Health and Medical Research Council of Australia

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O'Donnell, S.R., Wanstall, J.C. The importance of choice of agonist in studies designed to predict β 2:β 1 adrenoceptor selectivity of antagonists from pA2 values on guinea-pig trachea and atria. Naunyn-Schmiedeberg's Arch. Pharmacol. 308, 183–190 (1979). https://doi.org/10.1007/BF00501381

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  • DOI: https://doi.org/10.1007/BF00501381

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