Cytological analysis of radiation-induced DNA amplification in C57BL/6 mice

Inbred mouse strain C57BL/6 pre-treated with or without the drug with suspected anticancer activity, DADH (N, N'-Diacetyl-1, 6-Diaminohexane) by daily feeding for five consecutive days to a total dose of 1 mmol of the drug in aqueous solution, were exposed to an acute dose of 1 Gy gamma radiation. Appropriate controls without radiation were maintained both for water and DADH-fed groups of animals. At 18 and 36 h post-irradiation the animals from all four groups (designated as A to D with each group having six animals) were sacrificed and their bone marrows were cultured for chromosomal analysis. Special emphasis was put on the estimation of the frequency of occurrence of extra chromosomal elements, such as minutes, single or double (DMS) as a possible assay for radiation-induced DNA amplification (presumably representing the proliferation specified genes(?) causing initiation of a very early tumourigenesis event). Gamma irradiation alone yielded the highest frequency of such minute chromosomal structures concerned (DMS), which was significantly reduced by DADH pre-treatment. The preliminary cytological data are discussed in the light of current information on DNA amplification pertaining to carcinogenic induction.