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  • Title: In vivo receptor binding of iodinated beta-adrenoceptor blockers.
    Author: Eckelman WC, Gibson RE, Vieras F, Rzeszotarski WJ, Francis B, Reba RC.
    Journal: J Nucl Med; 1980 May; 21(5):436-42. PubMed ID: 6103024.
    Abstract:
    Six radiolabeled beta-adrenoceptor blocking agents with a range of affinity constants were evaluated as radioindicators for adrenoceptors in guinea-pig heart and lung. All concentrated in the heart and lung at levels in excess of 0.1% dose/g tissue. On the basis of displacement studies using propranolol, two of the six compounds showed beta-adrenoceptor binding in the lung, and one, H-3 carazolol, showed receptor binding in the heart. These results agree qualitatively with a bi-molecular reversible equilibrium model, and suggest that the beta-adrenoceptor blockers as a group will not be useful in vivo probes of receptor concentration in the heart because of the low affinity constants and high levels of nonreceptor binding associated with the present-day clinical beta blockers. Beta-adrenoceptor blocking agents with affinity constants in excess of 10(9) will be needed to give heart-to-blood ratios of 10.
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