RADIOACTIVE IODINE INDUCES CLASTOGENIC AND AGE-DEPENDENT ANEUGENIC EFFECTS IN LYMPHOCYTES OF THYROID-CANCER PATIENTS AS REVEALED BY INTERPHASE FISH

After the Chernobyl nuclear accident, a dramatic I-131-related increas e in the incidence of thyroid cancer has been reported in exposed chil dren. However, little is known about the eventual genotoxic effects of I-131 in exposed humans. Thyroid cancer patients are usually treated with I-131 and, therefore, they provide us with an opportunity to stud y cytogenetic damage induced by known doses of this radionuclide. FISH techniques have been employed to study the origin of micronuclei as w ell as X chromosome nondisjunction and X chromosome numerical abnormal ities in lymphocytes from I-131-treated women suffering from thyroid c ancer. Blood was sampled before and 1 week after I-131 treatment, Cell s were analysed with either pancentromeric FISH to classify micronucle i or X chromosome centromere-specific FISH in mononucleated and binucl eated cells to evaluate X chromosome numerical abnormalities and non-d isjunction respectively, Our data indicate that I-131-induced clastoge nic and age-dependent aneugenic effects in the lymphocytes of exposed patients. The X chromosome was not preferentially involved in the aneu genic effect induced by I-131. It is concluded that besides its major clastogenic effect, I-131 can also induce an X chromosome-independent aneugenic activity mainly in patients with spontaneous proneness to ch romosome loss.