UNSCHEDULED DNA SYNTHESIS IN THE GERM CELLS OF MALE MICE IN VIVO

抄録

Unscheduled DNA synthesis (UDS) was studied by a quantitative autoradiographic technique in vivo in the germ cells of male mice after exposure to various mutagens. In the first experiment, we examined the most active cell stage for UDS in mouse spermatogenesis after treatment with methyl methanesulfonate (MMS) or iso-propyl methanesulfonate (iPMS). The UDS in the male germ cells reached plateau level within 2-6 hours after treatment. The activity of UDS induced by the chemicals was highest in early spermatids per DNA content, and in the late pachytene stage per cell among the various stages of germ cells. In the second experiment, 10 compounds, mostly known chemical mutagens, were tested at different doses. The numbers of grains in diakinesis and metaphase-I (dia and M-I) were counted 2 days after treatment. Although MMS, 4-hydroxyaminoquinoline-1-oxide (4-HAQO), ethyl methanesulfonate (EMS) and iPMS induced strong UDS in this order, Mitomycin C (MC), 2-acetylaminofluorene (2-AAF), m-phenylenediamine (mPDA) and dimethyl nitrosoamine (DMNA) did not clearly induce UDS. Furylfuramide (AF-2) and busulfan had only slight effects.