title: The use of short-term tests to measure the preventive action of reducing agents on formation and activation of carcinogenic nitroso compounds.
abstract: The effect of reducing agents on the nitrosation of methylguanidine (MG) and on the in vitro activation of dimethylnitrosamine (DMN) was examined by measuring DNA-repair synthesis (unscheduled incorporation of [3h]TdR), shifts in alkaline sucrose gradients, frequency of chromosome aberrations, and clone-forming capacity of cultured human fibroblasts. The reducing agents examined were sodium ascorbate, cysteine, cysteamine, and propyl gallate. Since the short-term bioassays used can be quantitated, it has become relatively easy to detect the inhibitory action of reducing compounds on the nitrosation reaction of MG and metabolic activation (with S-9 preparation) of the precarcinogen DMN, to measure their effective dose range, and to establish the most effective ratios between inhibitory agent and reactant. The results indicate that DNA-repair synthesis is a suitable short-term test for studying the numerous combinations and premutations between several carcinogenic or non-carcinogenic agents, and for estimating the capacity of inhibitory agents to affect formation and activation of chemical carcinogens.
mesh_terms: D000293:Adolescent; D000328:Adult; D000818:Animals; D001205:Ascorbic Acid / Q000494:pharmacology*; D002478:Cells, Cultured; D002869:Chromosome Aberrations; D003543:Cysteamine / Q000494:pharmacology*; D003545:Cysteine / Q000494:pharmacology*; D004260:DNA Repair; D004128:Dimethylnitrosamine / Q000037:antagonists & inhibitors; D004347:Drug Interactions; D005707:Gallic Acid / Q000031:analogs & derivatives*; D006801:Humans; D066298:In Vitro Techniques; D051379:Mice; D009603:Nitroso Compounds / Q000037:antagonists & inhibitors*; D011435:Propyl Gallate / Q000494:pharmacology*
chemical_list: D009603:Nitroso Compounds; D003543:Cysteamine; D005707:Gallic Acid; D011435:Propyl Gallate; D003545:Cysteine; D004128:Dimethylnitrosamine; D001205:Ascorbic Acid