MONITORING HPRT MUTANT FREQUENCY OVER TIME IN T-LYMPHOCYTES OF PEOPLEACCIDENTALLY EXPOSED TO HIGH-DOSES OF IONIZING-RADIATION

Modern technologies have provided the opportunity to monitor mutations in people in vivo. The subjects of this study were accidentally expos ed to (137)Cesium in a radiological accident that occurred in Septembe r 1987 in Goiania, Brazil, during which more than 150 people received doses greater than 0.1 Gy and as high as 7 Gy. The objective of this s tudy was to determine how long the hprt mutant T-cells in the peripher al blood contribute to mutant frequency by examining the time-course o f the T-lymphocyte response to ionizing radiation. This report describ es the results obtained over a period of 2.3 to 4.5 years subsequent t o the accident, from 11 subjects with doses ranging from 1 to 7 Gy, an d from nine control subjects selected from the same population. The me an ln MF (+/-SE) of the control group was 2.5 (+/-0.2) + ln 10(-6) The exposed group had a significantly increased mutant frequency; the mea n In MF (+/-SE) were 3.3 (+/-0.3) + ln 10(-6), 2.8 (+/-0.2) + ln 10(-6 ), and 2.3 (+/-0.2) + ln 10(-6), in the years 1990-1992 respectively. Based on the decline of mutant frequency and using Buckton's models [B uckton et al. (1967): Nature 214:470-473], we demonstrated that mutant T-cells have a short-term memory with a half-life of 2.1 years. This relatively short half-life limits the effective use of the hprt assay as the method of choice to monitor past exposure. The data also demons trate a positive correlation with age, and an inverse correlation with plating efficiency. (C) 1996 Wiley-Liss, Inc.