Abstract

Bredinin, a new nucleoside antibiotic, inhibited multiplication of several mammalian cell lines in culture and had a cytotoxic effect on L5178Y cells. Growth inhibition by bredinin was prevented by guanosine 5'-monophosphate (GMP), guanosine, or guanine but not by other purine or pyrimidine nucleotides, nucleosides, or bases. Inhibition by bredinin at a low concentration was completely prevented by 4 x 10 -5 M GMP; but at higher concentrations of bredinin the inhibition was not reversed even when the concentration of GMP was raised. Addition of GMP after cellular damage had occurred produced no effect on the damaged cells but it prevented further damage. Bredinin caused marked chromosomal aberrations such as breakages, translocations, and fragmentation in L5178Y cells.