A comparative study of the effect of aflatoxin B and actinomycin D on HeLa cells

1. The cytotoxic effects of aflatoxin B(1) on HeLa cells were examined and effects of short exposures of the cells to the toxin were found to be reversible. 2. Aflatoxin B(1) inhibited the synthesis of both ribosomal and heterodisperse RNA. It is proposed that the toxin's mechanism of action on ribosomal RNA synthesis is related to its inhibitory effect on the maturation of the 45s-ribosomal-RNA precursor. 3. Protein synthesis is inhibited to a greater extent by aflatoxin B(1) than by actinomycin D. In contrast with actinomycin D, aflatoxin B(1) was shown to disaggregate polyribosomes directly.