The effect of sodium fluoride on DNA synthesis, mitotic indices and chromosomal aberrations in human leukocytes treated with trenimon in vitro.

Human leukocyte cultures were set up with Ham's F-10 medium and stimulated with PHA-M. Treatment of the cells in G1 from 15-20 h with 0.5 X 10(-6) M Trenimon resulted in a considerable cell cycle delay, as measured by [3H]-TdR autoradiography and determination of mitotic indices. Under these conditions only few cells incorporated the tracer at the same time as most cells did in untreated cultures. However, this did not lead to a mitotic activity at the same time as obtained in controls. Most of the treated cells started their DNA synthesis and mitotic activities with a delay of around 20 h, as compared with the controls. Continuous treatment of the cells with 10(-3) M NaF had no effect on [3H]TdR labelling or mitotic indices in otherwise untreated cultures, but led to an impressive effect on DNA synthesis in Trenimon-treated cultures, without a considerable effect on the mitotic indices. This finding could be explained as due to a lower alkylation in cellular DNA in the presence of NaF. More cells can start with their DNA synthesis, although they are, like Trenimon-treated cultures, incapable of completing it normally. Analysis of the effect of NaF on chromosome aberrations induced by Trenimon revealed that pre-, simultaneous and post-treatments significantly enhanced the frequency of undamaged mitoses. Continuous fluoride treatment also protected the cells from Trenimon-induced damage, but the effect was not significant, possibly because of heavily damaged mitoses which appeared under these conditions. We interpret our findings as an indication of a real anti-mutagenic activity of NaF.