Comparisons of dose-response parameters for radiation-induced acentric fragments and micronuclei observed in cytokinesis-arrested lymphocytes.
We employed cytochalasin B to block cytokinesis in human lymphocytes exposed to 220 kV X-radiation. When 3 micrograms/ml of cytochalasin B was used, most cells escaped the block whereas at 6 micrograms/ml greater than 90% of the mitogen-responsive cells became binucleate. Using the higher concentration of cytochalasin B, we observed a linear-quadratic (i.e. Y = gamma + alpha D + beta D2) dose dependency for X-ray-induced micronuclei (MN) in preparations from three donors. When dose-response parameters were compared with those for total acentrics scored in first division metaphases, we observed no significant differences in estimates of the background (gamma) or linear (alpha) coefficients, but a 2-fold reduction in the beta coefficient for MN. We interpret our data as providing evidence that radiation-induced micronuclei are derived from acentric fragments (AF); that virtually all AF are recovered as MN in binucleate interphase daughter cells at low radiation doses; and that for our data, the relative proportion of AF that will be observed as independent MN decreases by a constant factor of approximately one-half as radiation dose increases.
Littlefield
L G
LG
Radiation Emergency Assistance Center/Training Site (REAC/TS), Oak Ridge Associated Universities, TN 37831.
Sayer
A M
AM
Frome
E L
EL
D000328:Adult; D002455:Cell Division / Q000187:drug effects / Q000528:radiation effects*; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism / Q000528:radiation effects*; D002478:Cells, Cultured; D002869:Chromosome Aberrations; D003571:Cytochalasin B / Q000633:toxicity; D004305:Dose-Response Relationship, Drug; D004307:Dose-Response Relationship, Radiation; D006801:Humans; D008213:Lymphocyte Activation / Q000187:drug effects / Q000528:radiation effects*; D015162:Micronucleus Tests; D014965:X-Rays
D003571:Cytochalasin B