| Abstract: | Preimplantation mouse embryos were exposed in vitro to 3H-thymidine (25, 100, or 250 Bq/ml) or ultraviolet (UV) light (1.35 or 4.05 J/m2), either alone or in combination with caffeine (1 mM with 3H-thymidine and 0.5 mM with UV light). Exposure to 3H-thymidine lasted for 2 days, from the two-cell stage to the late morula/early blastocyst stage, and UV radiation was applied acutely at the late morula/early blastocyst stage. The effects were quantified by the sister chromatid exchange (SCE) assay. All three agents induced SCEs when used singly. 3H-thymidine was effective in inducing SCEs only at 250 Bq/ml, whereas UV light was effective at both fluences. Although caffeine did not induce SCEs when it was added before exposure to bromodeoxyuridine (BrdUrd), which is used to visualize SCEs, it did induce SCEs when present during the entire culture period (3H-thymidine experiments) or during incubation in BrdUrd (UV experiments). Caffeine markedly enhanced the SCE-inducing effect of UV light but did not influence the effect of 3H-thymidine. |
