Radioiodinated branched-chain fatty acids: substrates for beta oxidation? Concise communication.

Branched-chain iodinated fatty acids have been proposed for use as myocardial imaging agents. Several omega- iodoalkyl and omega- iodoaryl beta-methyl branched fatty acids have been synthesized and tested in rats. Myocardial activity levels at t = 5 min are affected by chain length for both alkyl and aryl acids, with chain lengths of 16 carbons possessing higher levels of activity than shorter lengths. Branching significantly lowers heart-to-blood ratios relative to straight-chain analogs. The degree of branching also affects radioactivity levels. Monoalkylation at the beta-carbon does not reduce the levels for omega- iodoalkyl fatty acids, but dialkylation reduces the levels significantly. Branching in the omega- iodoaryl series of fatty acids altered the time course of activity in the myocardium from a level of activity decreasing with time for the straight-chain acid to an essentially constant level of activity for the branched analogs.