Comparison of 11C and 14C-labeled fatty acids and their beta-methyl analogs.

1-[14C] beta-methylheptadecanoic acid ( [14C]BMHDA) was compared to 16-[14C]palmitic [( 14C]PA) acid for its biodistribution in rats, to determine whether an analogue designed to be trapped as a metabolite of the beta-oxidation metabolic process in the myocardium could be used to assess myocardial metabolic integrity. A heart concentration of 2.82 and 6.18% I.D./g at 5 and 60 min was observed for [14C]BMHDA, while [14C]palmitic acid was 2.65 and 0.89% I.D./g at 5 and 60 min respectively. However the myocardial concentration at 24 h was 0.4% I.D./g, indicating clearance of the tracer from the heart. Quantitative autoradiographic studies confirmed the highest heart concentration of [14C]BMHDA at 60 min, compared to other organs.