Formation of superoxide radicals in isolated cardiac mitochondria: Effect of low oxygen concentration

Formation of superoxide radical in isolated rat heart mitochondria under controlled oxygenation has been studied by spin trapping and EPR oxymetry. Lithium phthalocyanine and perdeuterated Tempone-D-¹⁵ N ₁₆ were used to determine the oxygen concentration. Tiron was used as a spin trap. By varying the oxygen content in the reaction medium, we have shown that isolated heart mitochondria can produce superoxide even at an oxygen partial pressure of 17.5 mmHg, though at a rate considerably lower than under normal conditions. Raising the oxygen concentration increases the rate of superoxide generation.