Heterogeneity of chromosome damage in beta-thalassaemia traits. An evaluation of spontaneous and gamma-ray-induced micronuclei and chromosome aberrations in lymphocytes in vitro after G0 and G2 phase irradiation.

This study is an attempt to evaluate the chromosomal radiosensitivity of beta-thalassaemia traits compared with healthy individuals from the general population, necessitated by the fact that beta-thalassaemia trait is present in 1-17% of different population groups in India and the chances of encountering them in radiation and chemical related industries do exist. Spontaneous chromosome aberration frequencies in peripheral blood lymphocytes from beta-thalassaemia traits were found to be in the normal range, whereas significantly higher frequencies of micronuclei (MN) were observed in thalassaemia traits. Based on MN frequency at 2 Gy, beta-thalassaemia traits fall into two distinct categories. A hypersensitive group with significant increase in radiation-induced MN over the control group, and a second group with MN frequency slightly above normal individuals. Even when compared with the fitted data at 2 Gy obtained from the pooled results of extensive dose-response investigations from 0.5-5 Gy gamma-rays with normal donors for MN, dicentrics and total aberrations, the difference between the means of MN frequencies in beta-thalassaemia traits and normals is significant. MN have a higher control level, a higher value for the alpha component, and much lower value for the beta component, when compared with total aberrations. Both in 2-Gy irradiated G0 lymphocytes as well as 0.5 and 1-Gy irradiated G2 lymphocytes, there is a certain degree of hypersensitivity when the results are meaned over a number of individuals, but some individuals overlap within the normal range. In G0 irradiated lymphocytes from beta-thalassaemia traits, the dicentric chromosome is the only aberration category in which the yield is seen to rise. The heterogeneity in chromosomal radiosensitivity observed in beta-thalassaemia traits is discussed in terms of the oxidative damage consequent to the genetic and biochemical features peculiar to the beta-thalassaemia trait cell. The data presented herein may have wider implications in radiation protection.