INTRINSIC RADIOSENSITIVITY OF ADULT AND CORD-BLOOD LYMPHOCYTES AS DETERMINED BY THE MICRONUCLEUS ASSAY

Predictive radiosensitivity testing necessitates rapid and reliable assays of radiosensitivity. We assessed the lymphocyte micronucleus assay as such an assay. We performed repeated experiments on lymphocytes from 10 healthy donors. Levels of radiation-induced micronuclei were measured following exposures of up to 4 Gy Xrays. When measuring the slope of the dose-response, we have found more variation between individuals than between repeated experiments on the same individual (F value 12.31, P < 0.001). There is also greater interindividual variation in the data following a single dose of X-rays of 2 Gy (F value 3.54, P < 0.01) and of 4 Gy (F value 7.55, P < 0.005). We performed the micronucleus assay on five different samples of cord blood lymphocytes (CBLs). Their radiosensitivities were compared with the mean radiosensitivity of the lymphocytes from the normal group of donors. Comparing the level of micronuclei induced by 2 Gy, only CBL1 (P < 0.01) and CBL2 (P < 0.02) were more radiosensitive than the mean of the adult lymphocytes. At 4 Gy, CBL1 (P < 0.001), CBL2 (P < 0.05), CBL3 (P < 0.01) and CBL5 (P < 0.01) were more radiosensitive than the mean radiosensitivity of the adult lymphocytes, This was also shown when the slope of the dose-response curves were measured. We conclude that the lymphocyte micronucleus assay shows more variability when applied to lymphocytes from different individuals than when repeatedly applied to lymphocytes from the same individual, a requirement for the determination of individual radiosensitivity.