Effect of nitroglycerin on the free radical formation of myocardial mitochondria impaired by ethanol. Studies by electron spin resonance (ESR) spectrometry.

In order to investigate the direct metabolic effect of nitroglycerin on myocardium, its effect on mitochondrial free radical formation was studied in vitro, using the dog heart mitochondria impaired by ethanol. Free radical concentrations in state 4 respiration or the ratio of free radical concentrations in state 4 to state 1 was used as an index of mitochondrial function. Free radical concentrations were represented as ESR intensity. In normal control, ESR intensity increased from 0.115 +/- 0.030 (mean +/- SD) per mg protein in state 1 to 0.178 +/- 0.017 in state 4 (p less than 0.001). When mitochondria were treated with 10(-4) M ethanol, on the other hand, ESR intensity decreased from 0.163 +/- 0.34 in state 1 to 0.137 +/- 0.019 in state 4 (p less than 0.05). When mitochondria were treated with 10(-6) M nitroglycerin, in spite of the presence of 10(-4) M ethanol, ESR intensity increased from 0.124 +/- 0.23 in state 1 to 0.153 +/- 0.024 in state 4 (p less than 0.05). ESR intensity in state 1 was increased by the treatment of ethanol (p less than 0.05), whereas ESR intensity in state 4 was decreased (p less than 0.001), and these effects were prevented by nitroglycerin (p less than 0.05). The ratio of ESR intensity in state 4 to state 1 demonstrated more remarkably the effects of ethanol and nitroglycerin. Ethanol reduced the ratio from 1.65 +/- 0.47 in the control to 0.86 +/- 0.13 (p less than 0.001) and the reduction was prevented by nitroglycerin to 1.25 +/- 0.23 (p less than 0.01). It is concluded that nitroglycerin prevented the impairment of free radical formation of the mitochondria induced by ethanol, presumably by a mitochondrial membrane-stabilizing action.