Comparative evaluation of the in vitro micronucleus test and the comet assay for the detection of genotoxic effects of X-ray radiation

The genotoxic effects of X-ray radiation on human lymphocytes were measured using the single cell gel electrophoresis (SCGE) assay (comet assay) and the cytokinesis-blocked micronucleus (CBMN) test; both were carried out in vitro on isolated human lymphocytes in order to compare the relationship and sensitivity of these two detecting methods. The radiation-doses were 0.00, 0.02, 0.05, 0.10, 0.25, 0.50, 1.00 and 2.00 Gy. In the comet assay, the average comet length (38.6+/-0.8 mu m) of 0.05 Gy was significantly longer than that (29.4+/-1.1 mu m) of 0 Gy (P<0.01), moreover, the average comet length increased with the dose of X-ray radiation. In the CBMN, both the average micronucleus rate (MN) and micronucleated cell rate (MNC) of 0.05 Gy were 11.5+/-4.5 parts per thousand, which showed no difference with that (7.5+/-0.5 parts per thousand) of 0 Gy (P>0.05). The lowest dose, which induced significant increase of average MN and MNC, was 0.25 Gy. The average MN and MNC rates increased with radiation-dose. The results showed that there was correlation between SCGE and CBMN, and the sensitivity of SCGE was significantly higher than that of CBMN. (C) 2000 Elsevier Science B.V. All rights reserved.