Myocardial uptake and turnover of 17-(123I)-iodoheptadecanoic acid, injected i.v., was studied in rats. Kinetics of radioactivity incorporated into myocardial tissue
and heart lipids as well as myocardial radioactivity recovered as123I iodide were determined. Maximal heart uptake of IHA (7.9% dose/g heart) was observed as early as 30 sec., p.i., followed
by mono-component elimination period. Already 10 to 30 sec p.i. 70 to 80% of total myocardial radioactivity was recovered
as123I iodide. IHA was incorporated only in modest amounts into myocardial phospholipids and triglycerides. Time course of total
myocardial radioactivity grossly paralleled that recovered as123I iodide. These findings indicate stringent limitations in utility of IHA as a tracer for assessment of β-oxidation.