Studies on the Reversal of 5-Fluorodeoxyuridine-Induced Mitotic Inhibition by Thymidine and Thymidine Analogues

Abstract

At concentrations of lo-' M and lo-' M, 5-fluorodeoxyuridine (FUDR) completely inhibits cell division in root tips of Vicia fnbn. Suppression of cell division by A4 FUDR is incomplete. I11 roots treated with lo-' A4 thymidine (TDR), the level of mitosis is unchanged. In 10.' A4 TDR, lo-' A4 5-bromodeoxyuridine (BUDR), or lo-' M 5-iododeoxyuridine (IUDR), there is some decline in the mitotic index, particularly at later time periods.After a 25-hour treatment with lo-' M FUDR, roots do not recover for more than 2 days in water. Recovery is faster in T D R . Thcre is a slight enhancement of recovery in lo-' &I T D R and more rapid recovery at higher concentrations. The T D R analogues, BUDR and IUDR, are also somewhat effective in reversing FUDR-induced mitotic inhibition. T D R itself is most effective, followed by BUDR and IUDR, in that order. Renewed cell division, however, is often only temporary.When administered simultaneously with lo-' h4 FUDR, TDR, at higher concentrations, provides some protection from mitotic inhibition. The protection from 10-a &I FUDR offered by simultaneous exposure to IUDR is slight. With simultaneous exposure to 10" A? FUDR and lo-' A4 BUDR, a decline in the level of mitosis is followed by partially synchronous cell divisions.

CELL ARREST IN Gl AND G2 OF THE MITOTIC CYCLE OF VICIA FABA ROOT MERISTEMS

“…Cells in G2 do not require further DNA synthesis before dividing and, therefore, if treated with either FUdR or 5-AU when provided sucrose, little or no effect on the initial mitotic index should be observed. Both FUdR and 5-AU are known to inhibit DNA synthesis in Vida, but neither inhibitor prevents the division of cells from G2 (Socher and Davidson, 1971a, b;Hoffmann, 1970;Bell and Wolff, 1966;Jakob and Trosko, 1965) . The results shown in Fig.…”