KINETICS OF MICRONUCLEI INDUCED BY (125)IDU IN CELLS OF 2 LINES

The kinetics of the formation of cells carrying micronuclei (MN) after one doubling time (t(d)) incorporation of I-125-iododeoxyuridine ((12 5)IdU) to Chinese hamster ovary (CHO) and rat anterior pituitary tumor (GC) cells was studied. Uptake of (125)IdU by cells of both cell line s was linearly dependent on the concentration of extracellular I-125 a ctivity. The postlabeling time-dependent decrease in cellular activity of (125)IdU was exponential in CHO cells and approximately linear in GC cells. The maximum yield of MN was seen during the second and third t(d) after (125)IdU incorporation. The frequency of cells with micron uclei increased monotonically with dose in the interval (1, 40) I-125 decays cell(-1) t(d)(-1) . The dose-response relationship could be fit ted by straight lines with slopes of 1.0 (CHO) and 1.2 (GC) on the sub interval (1, 10) and of 0.6 or 0.5, respectively, for the subinterval (10, 40). Below one I-125 decay cell(-1) t(d)(-1), the mean d frequenc y of micronucleated binuclear cells was significantly lower than (CHO) or equal to (GC) the control. On average, one I-125 decay/cell induce d 0.95 +/- 0.5% (CHO) or 1.0 +/- 0.5% (GC) of micronucleated binuclear cells.