Development of Glycoside-Bound Radiopharmaceuticals : Novel Radioiodination Method for Digoxin

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We combined 2-hydroxy-3-methylbenzoylhydrazide (HMBH) with glycosides as a novel method for the radioiodination of physiologically active glycosides. This method was tested using digoxin, which is one of the cardiac glycosides. A digoxin-HMBH conjugate was synthesized by periodate cleavage of the third sugar ring, and was readily radiolabelled with Na[¹²⁵I] by the chloramine-T method. ¹²⁵I labelled digoxin-HMBH conjugate retained Na⁺, K⁺-ATPase binding in vivo and in vitro, and also retained immunoreactivity to an anti-digoxin antibody. Thus, this ¹²⁵I labelled digoxin-HMBH conjugate represents a potential radiopharmaceutical for Na⁺, K⁺-ATPase imaging, as well as for the radioimmunoassay of digoxin.