In vitro and in vivo characterization of 4-[125I]iododexetimide binding to muscarinic cholinergic receptors in the rat heart

K. Matsumura, Y. Uno, U. Scheffel, A. A. Wilson, R. F. Dannals, H. N. Wagner

Research output: Contribution to journalArticle

Abstract

4-[125I]iododexetimide binding to muscarinic cholinergic receptors (mAChR) was evaluated in the rat heart. 4-[125I]iododexetimide displayed high in vitro affinity (Kd = 14.0 nM) for rat myocardial mAChR. In vivo, there was high accumulation of 4-[125I]iododexetimide in the rat atrium and ventricle which could be blocked by ~60% by preinjection of atropine. In contrast, accumulation of the radiolabeled stereoisomer, 4-[125I]iodolevetimide, was 63% lower than 4-[125I]iododexetimide and was not blocked by atropine. The blood clearance of 4-[125I]iododexetimide was rapid, providing heart-to-blood ratios of up to 14:1; however, heart-to-lung and heart-to-liver ratios were below unity. The data indicate that 4-[125I]iododexetimide binds potently to rat mAChR. However, since nonspecific binding is relatively high, it is not clear whether iododexetimide labeled with 123I will be useful in SPECT imaging studies of myocardial mAChR. Further studies in humans are indicated.

Original languageEnglish (US)
Pages (from-to)76-80
Number of pages5
JournalJournal of Nuclear Medicine
Volume32
Issue number1
StatePublished - 1991

ASJC Scopus subject areas

  • Radiology Nuclear Medicine and imaging

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