Kinetics of radioiodinated heptadecanoic acid and metabolites in the normal and ischaemic canine heart.

This study was undertaken to elucidate if the myocardial elimination rate of the radioactivity after administration of radioiodinated heptadecanoic acid was related to beta-oxidation of the fatty acid or related to washout of free radioiodide. In samples of normal and ischaemic myocardium the distribution of the radioactivity over free radioiodide, heptadecanoic acid and lipids was determined. In normal myocardium the major component was free radioiodide, only a small percentage being heptadecanoic acid. In ischaemic myocardium more radiolabelled lipids were present and less free iodide when compared with normal myocardium. The percentage heptadecanoic acid was slightly increased. It is concluded that radioiodinated heptadecanoic acid behaves like the natural analogues regarding uptake and distribution. However, washout of free radioiodide determines the elimination rate as observed during a scintigraphic study.