Metabolism of palmitic acid in perfused rat heart

¹ Department of Medicine, Harvard Medical School, and Baker Clinic Research Laboratory, Boston, Massachusetts, and Department of Medicine, University of Toronto, Toronto, Canada

Metabolism of fatty acid was studied in the isolated rat heart perfused with albumin-bound palmitate-C¹⁴. Uptake of fatty acid by the heart was related to the concentration of fatty acid present and the molar ratio of fatty acid to albumin in the perfusion fluid. Disappearance of lipid-bound radioactivity from the perfusion fluid (palmitate-C¹⁴ uptake) was consistently greater than disappearance of titratable fatty acid. This was attributed to failure of equilibration of unlabeled "endogenous" fatty acid on albumin with added palmitate-C¹⁴ and possibly to release of unlabeled fatty acid from the heart to the perfusion fluid. The principal fates of palmitate-C¹⁴ were C¹⁴O₂ and saponifiable tissue lipid. The maximal rate of recovery of palmitate-C¹⁴ as C¹⁴O₂ was equivalent to 83% of total CO₂ production of the isolated perfused heart in 30 min.