Abstract
The potent carcinogen N-nitrosodiethanolamine (NDELA) which is nonmutagenic in standard modifications of the S. typhimurium/mammalian microsome assay, can be activated effectively by alcohol dehydrogenase/NAD (ADH/NAD) to intermediates which are directly mutagenic in strains TA 98 and TA 100. The expected metabolites N-nitroso-2-hydroxymorpholine (NHMor), N-nitroso-(2-hydroxyethyl)-glycine (NHEG), N-nitrosoiminodiacetic acid (NIDA), and glycolaldehyde were assayed for their direct mutagenic activities in S. typhimurium TA 1535, TA 98, and TA 100. All compounds were clearly mutagenic in TA 100, but different specificities were observed for the other strains. NDELA and its putative mutagenic metabolites were also tested for induction of genotoxic activities by determination of DNA single strand breaks in primary rat hepatocytes. In these cells, NDELA and NHMor were clearly genotoxic, whereas NHEG and NIDA were inactive. In contrast, when assayed for the induction of selective DNA amplification NDELA and its metabolites were not found to induce SV40 DNA synthesis in SV40-transformed Chinese Hamster cells. The compounds were also assayed for induction of DNA single strand breaks in the liver after a single oral application to rats. NDELA and NHMor were about equally active in this in vivo test, whereas NHEG, NIDA and glycolaldehyde were inactive. Differences in biological activity in the cultivated cells, as compared to hepatocytes or to the in vivo situation may most probably be due to differences in metabolism and/or pharmacokinetics.