Actinomycin D cytotoxicity for mouse peritoneal macrophages and effect on lactate dehydrogenase-elevating virus...

Treatment of lactate dehydrogenase-elevating virus(LDV)-infected mouse peritoneal macrophage cultures with actinomycin D (1 microgram/ml) resulted in a progressive reduction in the formation of LDV-specific RNA and mature virus as the time of incubation with actinomycin D increased beyond 2-3 h. This effect, however, seemed to reflect an unusual sensitivity of macrophages to toxic effects of actinomycin D. Macrophage cytotoxicity and lysis became apparent 3-4 h after addition of actinomycin D; the initiation of synthesis of Sindbis virus RNA, which is insensitive to inhibition by actinomycin D in other cell culture systems, was also reduced in actinomycin-D-treated macrophages. Macrophages propagated in L-cell-conditioned medium were found to be less sensitive to actinomycin D cytotoxicity and, correspondingly, the initiation and synthesis of LDV RNA were less affected.