Sister Chromatid Exchanges in Human Lymphocytes Exposed to Ionizing Radiation during G 0

Abstract

Several authors have reported small, but statistically significant, increases in sister chromatid exchanges (SCE) in mammalian cells exposed to low-LET [linear energy transfere] radiation during culture in the presence of [3H]-thymidine or bromodeoxyuridine (BUdR). To determine whether ionizing radiation also induces lesions in the unsubstituted DNA of Go lymphocytes that lead to SCE in 2nd division metaphases, human lymphocytes were exposed to 150 or 300 R 60Co-.gamma. radiation prior to culture in the presence of phytohemagglutinin and BUdR. Increased frequencies of SCE were not observed in the irradiated cultures, either in 2nd division metaphases having ring and discentric chromosomes or those that did not have detectable chromosome aberrations. Increased frequencies of SCEs would not be observed in cultured lymphocytes from persons with in vivo exposures to radiation, and raise questions regarding the efficacy of ionizing radiation in inducing long-lived lesions in native DNA that can subsequently be expressed as SCE.