A note on the utility of Fischer-344 rat in the micronucleus test

Bone marrow smears from Fischer-344 rats possessed such a high incidence of basophilic granules that accurate detection of micronucleated erythrocytes was not possible. In contrast, preparations from Sprague-Dawley rats had far fewer such granules, so that the micronucleated marrow cells were clearly visualized and counted. The difference in the incidence of basophilic granules was attributed to strain differences in mast cell population size.