SPONTANEOUS AND RADIATION-INDUCED MICRONUCLEI IN ERYTHROCYTES FROM 4 SPECIES OF WILD RODENTS - A COMPARISON WITH CBA MICE

Almost 100 animals of 4 different species of small wild rodents (bank vole, Clethrionomys glareolus; field vole, Microtus agrestis; yellow-n ecked mouse, Apodemus flavicollis; and wood mouse, Apodemus sylvaticus ) were trapped in central Sweden and used in experiments to determine the spontaneous and radiation-induced frequencies of polychromatic (fM PCE) and normochromatic erythrocytes (fMNCE) from bone marrow (bm) and peripheral blood (pb) using flow cytometric analysis. The results wer e compared with those from similar experiments with CBA mice. The savi ng of time and labour by the use of the flow cytometer-based analysis was a prerequisite for this study in which about 135 million PCE were analysed. The mio species of voles had a mean background fMPCE (bm) of about the same value as CBA mice, while the yellow-necked mice had ab out five times higher fMPCE (bm). Wood mice had more than twice the fM PCE (bm) compared to CBA mice. Between individual animals in each of t he 4 species, the background fMPCE (bm) varied more than between indiv idual CBA mice, and the elimination of micronucleated erythrocytes was considerable. When exposed to ionizing radiation, the voles did not s how a significant response. The response of the two Apodemus species w as similar to that of the CBA mice, although it varied between individ ual animals and was not correlated to their background fMPCE. This stu dy indicates that bank voles and field voles are unsuitable testing ob jects in the in vivo micronucleus assay. On the other hand, yellow-nec ked mice and wood mice seem to be useful in this test. Since the varia tion between individuals is considerable in wild Apodemus mice, large groups will be needed for obtaining statistically significant results when exposure to a genotoxic agent is low. Alternatively, repeated sam ples can be taken from individual wild mice to study the effect of a d ecreased exposure after keeping the animals for a period of time in an uncontaminated environment. (C) 1997 Elsevier Science B.V.