Comparative Susceptibility of Kidney and Gill Cells of Medaka Fish (Oryzias latipes) to Spontaneous and X-ray-induced Micronucleus Formation

Abstract

The frequency of micronucleated cells (MNCs) was measured in acridine orange (AO) stained kidney cells obtained from male and female medaka fish (Oryzias latipes) of known body weight before and after X-irradiation at a dose of 4 Gy. The MNC frequency in the kidney cells obtained from untreated and X-ray treated fish did not vary in correlation with the body weight in either gender, and neither did it show a significant gender-related difference. In both the untreated and treated groups, the number of MNCs in kidney cells per fish appeared to follow a Poisson distribution. These results are in agreement with those previously reported for the MNC frequency in gill cells of medaka fish. The average MNC frequency in kidney cells for the untreated fish was 0.4‰ (12/30000), which was significantly lower than 0.8‰ (24/30000) reported for gill cells. Similarly, a relatively lower frequency of X-ray-induced MNCs was evident for kidney cells (2.2‰; 69/30000) vs. gill cells (6.3‰; 191/30000). These results combined with previous reports support the use of AO to detect micronucleus formation in kidney cells, and further indicate that the kidney cell micronucleus assay can be used as a reliable and coincidently applied adjunct to the gill cell assay for medaka fish.