Imaging Agents

The development of gamma-emitting radiopharma ceuticals that could provide more accurate imaging of regional myocardial perfusion than thallium-20l would be useful in the early detection of coronary disease and assessment of therapy. Our approach to the development of such agents utilizes radiolabeled derivatives of drugs, such as the beta-adrenergic antagonists, that exert a selective pharmacologic effect upon the heart. The beta antagonists have the ability to decrease heart rate, myocardial contractility, and myocardial metabo lism. As defined by Lands et al. (I ), these are beta-i responses, and structure-activity relationship studies (2,3) have demonstrated that selective inhibition of these betaI responses can be achieved by the selective intro duction of functional groups onto the parent 3-phe noxyI-isopropylaminopropan-2-ol structure. For ex ample, the placement of hydrogen-bonding moieties in the para position of the phenoxy group, such as the acetamido and butyramido groups present in practolol