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

Summary

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 ∼ 3·0 Gy, with maximum protectible fractions of approximately 70 percent at DMSO concentrations of ≥ 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 = αD + βD². Data from duplicate cultures exposed in the presence of 1 m DMSO produce an excellent fit to the regression function modified as follows: where the ‘dose modifying’ factor Δ = 0·501. We interpret these findings as providing evidence that OH radical-mediated lesions in DNA account for ∼ 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 ∼ 6 × 10⁸ s⁻¹ for the rate of reaction of OH radicals with DNA targets involved in aberration formation.