Effect of different oxygen pressures and N,N'-diphenyl-p-phenylenediamine on Adriamycin toxicity to cultured neonatal rat heart myocytes.

The effect of different oxygen pressures and the antioxidant DPPD (N,N'-diphenyl-p-phenylenediamine) on Adriamycin (doxorubicin) cytotoxicity in highly purified cardiac myocytes was investigated to evaluate the involvement of free radicals in the mechanism of toxicity. Adriamycin exposure caused a time-dependent decrease in viability measured as intracellular potassium ion release or lactate dehydrogenase retention. Incubation of myocytes in 16, 172 or 834 microM oxygen during exposure to 200 microM Adriamycin for 6 hr killed 13, 42 and 56% of the cells in the respective cultures. DPPD prolonged viability in the latter two oxygen concentrations and protected against lipid peroxidation measured as production of malondialdehyde and 4-hydroxynonenal. Addition of superoxide dismutase decreased the Adriamycin-induced cell killing to 6% after a 4-hr incubation, as compared to 24% in cultures exposed to Adriamycin only. Adriamycin exposure decreased the concentration of reduced glutathione, and the toxicity of the drug was increased when glutathione reductase was inhibited by the addition of BCNU (1,3-bis-2-chloroethyl-1-nitrosourea). No significant effect on Adriamycin toxicity was observed after inhibition of glutathione synthesis by treatment with BSO (buthionine sulfoximine). It is concluded that free radicals play an important role in Adriamycin toxicity to heart myocytes, and that the cell killing mechanism is likely to be related to induction of lipid peroxidation.