EFFECT OF DIFFERENT OXYGEN PRESSURES AND N,N'-DIPHENYL-P-PHENYLENEDIAMINE ON ADRIAMYCIN(R) 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) cytotoxicit y 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 in tracellular potassium ion release or lactate dehydrogenase retention. Incubation of myocytes in 16, 172 or 834 mu M oxygen during exposure t o 200 mu M Adriamycin for 6 hr killed 13, 42 and 56% of the cells in t he respective cultures. DPPD prolonged viability in the latter two oxy gen concentrations and protected against lipid peroxidation measured a s production of malondialdehyde and 4-hydroxynonenal. Addition of supe roxide dismutase decreased the Adriamycin-induced cell killing to 6% a fter a 4-hr incubation. as compared to 24% in cultures exposed to Adri amycin only. Adriamycin exposure decreased the concentration of reduce d glutathione, and the toxicity of the drug was increased when glutath ione reductase was inhibited by the addition of BCNU (1,3-bis-2-chloro ethyl-1-nitrosourea). No significant effect on Adriamycin toxicity was observed after inhibition of glutathione synthesis by treatment with BSO (buthionine). It is concluded that free radicals play an important role in Adriamycin toxicity to heart myocytes, and that the cell kill ing mechanism is likely to be related to induction of lipid peroxidati on.