Dicentric in lymphocytes of residents of high background radiation area (HBTA) in the southern China occur as well as radiation-induced genomic instability by telomere dysfunction

Dicentric and translocations are produced in almost equal ratio in human peripheral blood cells after acute exposure to radiation. And cells with a dicentric chromosome are destined to die through cell division and therefore have no causative effects on diseases relating to DNA dmage, such as malignant tumors and congenital abornalities. On the other hand, cells with a translocation accumulate and could proliferate in the body without eliminated by cell division and therefore represent a potential risk of causing those diseases. However, Hayata et al. (2000) recently reported that the frequency of dicentric and centric ring chromosome increases with the cumulative dose in lymphocytes of residents in the naturally high background radiation area (HBRA) in the southerm China but not translocations. This result cannot be explained in the theory described above. It is meant that the induction mechanism of chromosomal aberration in the chronic exposure with lower dose rate differs from it in the acute exposure with higher dose rate. On the other hand, we recently found that the chromosome aberration induced by genomic instability in the progeny of irradiated cells is similat to that founded in lymphocytes of residents in HBRA. Although mechanism of genetic instability induced by radiations are not clear, we know that both the abnormal chromosomes in the progeny of irradiated cells and dose in lymphocytes of residents HBRA are not accompanied by fragment different from that induced by high doses of radiations. In this paper, we propose that radiation-induced delayed chromosomal instability is triggered by telomere dysfunction and that telomere is a critical target for induction of genomic instability by radiation. Dicentric in lymphocytes of residents in HBRA also seems to occur in the same mechanism as induction of genetical instability. (Author)