Studies on myocardial mitochondria in ischemic dog hearts by electron spin resonance (ESR) spectrometry.

The free radical concentration of myocardial mitochondria from ischemic dog heart was studied by means of electron spin resonance (ESR) spectrometry, and the effects of acute free fatty acid (FFA) mobilization on the process of electron transport and oxidative phosphorylation of ischemic dog heart mitochondria were studied using free radical concentration in the state IV respiration of the myocardial mitochondria as the indicators. 1. The intensity of the ESR signal of mitochondria (g = 2.003) from intact dog heart was significantly increased in state IV compared to state I (state IV/state I = 2.01 +/- 0.18). On the other hand, in state III, the ESR intensity was markedly decreased compared to state IV (state III/state IV = 0.33 +/- 0.06). 2. The ESR intensity ratio of state IV/state I of the mitochondria from the ischemic area of 1-hr ischemic dog heart decreased remarkably compared to normal group. 3. The ESR intensity ratio of state IV/state I of the mitochondria isolated from the ischemic area of 2-hr ischemic dog heart was significantly lower than in the control. The ESR intensity ratio of state IV/state III of this group was significantly higher than in the control. 4. In ischemic heart with high plasma FFA, the free radical concentration in state IV respiration of the myocardial mitochondria was significantly decreased as compared to ischemic heart without high plasma FFA. These results suggest that the free radical concentration of myocardial mitochondria in respective respiratory states may be useful for evaluation of functional disturbance of oxidative phosphorylation and the electron transfer system in myocardial mitochondria in ischemic heart. Sudden and abnormal rise of plasma FFA seems to further facilitate the uncoupling of oxidative phosphorylation in the mitochondria of the ischemic portion of the heart.