CARDIAC CELL TOXICITY INDUCED BY 4-HYDROPEROXYCYCLOPHOSPHAMIDE IS MODULATED BY GLUTATHIONE

Objective: Cardiac myocytes were exposed to 4-hydroperoxycyclophospham ide (4-HC, an activated derivative of cyclophosphamide) to assess whet her early ionic events are associated with the dose limiting toxicity of this chemotherapeutic agent. Methods: Primary cultures of embryonic chick cardiac myocytes were grown to confluency and then exposed to a medium containing 4-HC. Cellular sodium, potassium, and calcium conte nts were measured by atomic absorption spectrophotometry and related t o protein and ATP content. Pretreatment of the cultured heart cells wi th glutathione depleting or enhancing agents provided the basis for ev aluating the involvement of glutathione in the 4-HC-induced cytotoxici ty. Results: Administration of 150 muM 4-HC to cardiac myocytes result ed in increases in cellular sodium and calcium contents and decreases in potassium, ATP, and protein contents. Pretreatment of cardiac myocy tes with L-buthionine-SR-sulphoximine, a specific inhibitor of gamma-g lutarnylcysteine synthetase, depleted cellular glutathione to 12% of c ontrol and significantly reduced the minimum concentration of 4-HC cau sing cytotoxic changes. Conversely, elevation of cellular thiol conten t by the pretreatment of cardiac myocytes with glutathione monoethyl e ster (but not glutathione) provided protection against 4-HC induced cy totoxicity. Conclusions: Cellular glutathione concentration can marked ly influence the 4-HC induced changes in cellular ion content and ATP, which are early indicators of 4-HC induced cytotoxicity.