Modulation of Radiation-induced Chromosome Aberrations by DMSO, an OH Radical Scavenger. 1: Dose—response Studies in Human Lymphocytes Exposed to 220 kV X-rays

Abstract

Human G0 lymphocytes were exposed to 220 kV X-radiation in the presence or absence of DMSO, an efficient selective scavenger of OH radicals. Our studies demonstrate that DMSO affects a concentration-dependent modulation of induced asymmetrical aberrations in human lymphocytes exposed to .apprx. 3.0 Gy, with maximum protectible fractions of approximately 70 percent at DMSO concentrations of .gtoreq. 1 M. The dose dependency for dicentrics in lymphocytes acutely exposed to X-ray doses of 0.51 to 4.98 Gy in the absence of DMSO is adequately described by the linear-quadratic dose-response function Y = .alpha.D + .beta.D2. Data from duplicate cultures exposed in the presence of 1 M DMSO produce an excellent fit to the regression function modified as follows: Y(+DMSO)=.alpha.(.DELTA.D)+.beta.(.DELTA.D)2 where the ''dose modifying'' factor .DELTA. = 0.501. We interpret these findings as providing evidence that OH radical-mediated lesions in DNA account for .apprx. 50 percent of the dose dependency for dicentrics resulting from either one-track or two-track events, following exposures of non-cycling cells to moderate-to-high doses of low LET radiation. These data may be used in additional calculations to derive an estimate of .apprx. 6 .times. 108 s-1 for the rate of reaction of OH radicals with DNA targets involved in aberration formation.