Kinetics of 17-(123I) iodoheptadecanoic acid in myocardium of rats

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.