Histoautoradiographic detection of DNA repair synthesis in mouse liver following dimethylnitrosamine treatment using whole-body application of labeled thymidine.

DNA repair synthesis following dimethylnitrosamine (DMN) treatment in mouse liver was detected in vivo by means of histoautoradiography. This phenomenon was more significant around the acinus center (practically in all hepatocytes) than around the portobiliary space. Besides this also a decrease in semiconservative DNA synthesis was observed. Another finding was an increase of the background over the liver sections in the groups with DMN due to the altered metabolism of tritiated thymidine. This effect responsible for the difficulties encountered with in vivo autoradiographic detection of the repair synthesis was eliminated by prolonging the time between the 3H-thymidine application and sacrificing the animals. Based on this method, it is possible to develop a short-term assay for determining mutagenic and carcinogenic effects of various compounds.