Chromosome aberrations induced by daunomycin in human leukocyte cultures, with the apparent synergistic effect of arginine

Endogenous mutagens derived from amino acids

L-Cysteine, glutathione and the therapeutically used L-cysteine precursor, N-acetyl-L-cysteine, induced strong mutagenic effects in Salmonella typhimurium (reversion of the his- strains TA97, TA92 and TA104), when tested in the presence of subcellular kidney preparations. The tyrosine metabolites, levodopa (an ortho-hydroquinone) and homogentisic acid (a para-hydroquinone) reverted various his- strains as well. This mutagenicity did not require the presence of mammalian enzymes, and was relatively weak. The induction of gene mutations was also studied in mammalian cells (V79 Chinese hamster cells), using acquisition of resistance toward 6-thioguanine as the marker. L-Cysteine and N-acetyl-L-cysteine were found to be inactive, levodopa was weakly mutagenic, and homogentisic acid was strongly mutagenic (enhancing the mutation frequency 135-fold above background at an exposure concentration of 50 microM). This finding is striking as the urinary concentration of homogentisic acid is about 1000 times higher in patients with a genetic defect in homogentisic acid 1,2-dioxygenase (alkaptonuria). Genotoxic and carcinogenic effects of other amino acids and metabolites, reported in the literature, are discussed as well.

Interaction of daunomycin with meiotic chromosomes in Vicia faba

Daunomycin interferes with the meiotic cycle and structural integrity of chromosmes if administered to microsporocytes of Vicia faba during the meiotic prophase substages prior to diplotene. The principal cytological consequences of daunomycin treatment are as follows: induced achromatic lesions, chromosome fragmentation, terminal and interstitial deletions, loose or non-pairing regions, multivalent associations, reduced chromosome condensation, chromosome stickiness, dicentric and side-arm bridges and chromatid loops. A correlation between inhibition of DNA or RNA and the cytological manifestation of structural anomalies or unfolding of meiotic events is discussed.