Fig. 1.

Principles of in situ nick translation (ISNT) (a) and measuring UDS with autoradiography (b). For ISNT (a) tissue sections are incubated with a reaction solution containing buffer, MgCl₂, 2-mercaptoethanol, endonuclease-free E. coli DNA polymerase I, dATP, dGTP, dCTP and [³H]dTTP. The reaction is terminated by washing the slides with buffer. Afterwards sections are Feulgen-stained (which also removes all [³H] activity not incorporated into the nDNA; [160–162]), dipped into liquid photoemulsion, exposed, and developed. Poststaining can be performed with hematoxyline among other standard histologic stains. For measuring UDS with autoradiography (b) animals are injected with [³H]TdR and sacrificed 1 or 2 h later. Tissue sections are then also Feulgen-stained, dipped into liquid photoemulsion, exposed, developed, and poststained. Further details can be found in [39].