The effect of cyclophosphamide on the myocardial oxidase system of mitochondria

The authors studied the effect of immunosuppressive doses of cyclophosphamide (5 mg/kg b. w.) on the activity of myocardial NADH, succinate and cytochrome oxidases in the mitochondria of rabbit myocardium on two experimental models: a) after a single dose of cyclophosphamide (acute model); b) after cyclophosphamide given daily for a period of 10 weeks (chronic model). A single dose of cyclophosphamide did not affect the myocardial oxidase systems of mitochondria, whereas its chronic administration significantly increased the succinate oxidase activity and decreased cytochrome oxidase activity. The drug did not interfere with NADH- oxidase activity. It is concluded that long-term administration of cytostatic and immunosuppressive doses of cyclophosphamide may result in severe myocardial lesions on subcellular level. This should be taken into account in clinical practice.