[Specific inhibition of nuclear DNA synthesis with carcinogens (autoradiography studies of a short-term test)].
Six suckling growing CBA mice 14 days old (5-6 g of body weight) of the same litter served as test animals in each experiment. 0.1 ml of the dissolved chemicals (15-30 per cent of the LD50 were applied by i.p. injection to 3 animals each (experiment) and an equal number of mice was treated with the solvent only (control). 15 hours later the animals were given a single i.p. injection of 3H thymidine (2 microCi/g body weight) and 50 min afterwards they were sacrificed for autopsy and preparation of autoradiographs. Autoradiographs of nuclei of renal tubular epithelia and of liver epithelium were examined by visual silver grain counting (150 nuclei in each experiment and the same number in the corresponding control). We could demonstrate that carcinogenic compounds of different chemical classes partially inhibit the nuclear incorporation of thymidine in a significant manner over a time period longer than 24 hours. This inhibition may be due as a consequence of a prolonged S phase, expressed as a decrease of the mean of silver grain number per nucleus in comparison with the unaltered control. This decrease is used as a criterion for the suppressive effect of carcinogenic substances on the nuclear DNA synthesis rate. Noncarcinogenic compounds did not show this effect.
D000818:Animals; D001345:Autoradiography; D002273:Carcinogens / Q000008:administration & dosage / Q000494:pharmacology*; D004261:DNA Replication / Q000187:drug effects*; D007668:Kidney / Q000187:drug effects; D008099:Liver / Q000187:drug effects; D051379:Mice; D008808:Mice, Inbred CBA; D013936:Thymidine / Q000378:metabolism
D002273:Carcinogens; D013936:Thymidine
Spezifische Hemmung der nuklearen DNS-Synthese durch Karzinogene (Autoradiographische Studien zu einem Kurzzeittest).