Immunohistochemical detection of 4-hydroxyaminoquinoline 1-oxide-DNA adducts in mouse tissues in vivo.

4-Hydroxyaminoquinoline 1-oxide (4HAQO)-DNA adducts were immunohistochemically demonstrated in the nuclei of various organs of mice with the use of an antibody directed against 4HAQO-modified DNA. Specificity of the immunostaining was confirmed by several tests, including preincubation of the antibody with 4HAQO-modified DNA or related molecules and digestion of the sections with DNase. 4HAQO dissolved in isotonic solution and injected sc into an isolated portion of the mouse skin clamped off with ring-shaped forceps resulted in dose-dependent generation of DNA adducts in the nuclei of epithelial cells, fibroblasts, and panniculus carnosus cells. Nuclear staining was absent in animals given injections of isotonic solution only, and the intensity of staining correlated well with the level of unscheduled DNA synthesis demonstrated autoradiographically. 4HAQO-DNA adducts were observed in all target organs of 4HAQO tumorigenesis (i.e., lung, trachea, pancreas, uterus, vagina, skin, and colon) after injection of the carcinogen. Nuclear staining was absent or low in nontarget organs, including the liver and brain. Considerable variation was found in staining levels between cell types and different anatomic locations of cells within each target organ. The intensity of immunohistochemical staining correlated well with numbers of 4HAQO-DNA adducts measured by the radiolabeling technique.