Abstract
The Matsumoto Eosinophilic Shinshu (MES) rat originated from an inbred mutant colony of rats with spontaneous eosinophilia. As part of an investigation of the pathogenesis of the MES rat, we examined the haematology data for 106 males and 88 females and age-associated changes using an automated haematology analyser, flow cytometric analysis and morphological examination. The data at 10 weeks of age showed the MES rats had higher counts for eosinophils and neutrophils, slightly higher counts for lymphocytes, monocytes, basophils, and large unstained cells (LUCs), and slightly lower values for the erythrocytic parameters when compared with Sprague-Dawley (SD) rats. In data for MES rats aged 8 to 20 weeks, eosinophil counts increased with age up to 20 weeks together with some increased neutrophil counts. After 11 weeks of age, counts for lymphocytes, monocytes, basophils, and LUCs in the MES rats were also slightly increased. In female MES rats, flow cytometric analysis showed increased counts for pan-T+ cells, but blasts, abnormal granulocytes and lymphocytes were not detected morphologically. The MES rat characterized by the haematological findings could be a useful animal model for studies of hypereosinophilia.