Modification of radiation-induced genetic damage in Drosophila melanogaster male germ cells with nucleic acid precursors. 3. Effects on the premeiotic cells

Using a 2-day brood pattern, the effect of 5-bromodeoxyuridine (BUdR) or 5-bromodeoxycytidine (BCdR) pre-treatment on the radiation-induced yield of sex-linked recessive lethals and translocations was studied in the spermatocytes and late gonial cells (p.i. DNA synthesis cells) of D. melanogaster. The p.i. DNA synthesis cells were irradiated (I.2 kR γ-radiation) in the pre-meiotic or post-meiotic stage. Irradiation of p.i. DNA synthesis cells in the pre-meiotic stage resulted in enhanced lethal frequency with BUdR (3.0%) and BCdR (2.9%) over the other pre-treatment conditions: saline (S), thymidine (TdR) and deoxycitydine (CdR) in the spermatocytes but not in the late gonial cells. The radiosensitizing property was evident with BCdR even when the p.i. DNA synthesis cells were irradiated in the post-meiotic stage; but not with BUdR pre-treatment. Probable reasons for the contradicting results reported in the literature were discussed.