Carnitine distribution in subepicardial and subendocardial regions in normal and ischemic dog hearts

In order to evaluate the role of carnitine on fatty acid metabolism in subepicardial (Epi) and subendocardial (Endo) regions in ischemic heart, tissue levels of carnitine, free fatty acids (FFA), and adenosine triphosphate (ATP) were determined in ischemic, non-ischemic and border areas in dog hearts with acute regional ischemia. Acute regional ischemia was induced by ligation of the left anterior descending coronary artery for 15 min. In normal hearts, tissue carnitine levels were lower in Endo than in Epi. On the other hand, FFA levels were higher in Endo than in Epi. In ATP levels, no significant differences were observed between Endo and Epi. In acute regional ischemia, tissue carnitine levels decreased not only in ischemic and border areas but also in nonischemic area. And the levels were lower in Endo than in Epi in all areas. Tissue ATP levels were also lower in endo than in Epi in all areas. From nonischemic area toward the center of ischemic area, the difference in ATP levels between Endo and Epi became more prominent. Tissue FFA levels increased in ischemic and border areas, while no significant differences were observed between Endo and Epi. These results confirmed that Endo as metabolically more anaerobic than Epi even in normal heart and it became more prominent in the heart with acute regional ischemia.