Appearance of eosinophilic granule cells as pathological changes in the uteri of two aged virgin Donryu rats

The morphological features of cells containing eosinophilic granules (EG cells) present as pathological changes in the uteri of 2 aged virgin Donryu rats were described and compared with granulated metrial gland (GMG) cells of a pregnant rat. Microscopically, EG cells distributed diffusely from the mesometrial triangle to the subendometrium with partly focal accumulation in Case 1 and infiltrated diffusely from the endometrium to the serosa without any clumping in Case 2. They were large cells with eosinophilic and hyaline intracytoplasmic granules, positive for the periodic acid-Schiff reaction. Both EG and GMG cells reacted positively to concanavalin A, wheat germ agglutinin, and phytohemagglutinin on lectin histochemical investigation, although common results were not always obtained for immunohistochemistry. These results show that EG cells are morphologically similar to GMG cells, suggesting a possibility that EG cells are GMG cells. EG cells were without neoplastic properties or pronounced cell-proliferative activity. In Case 1, histological changes of the ovaries and vagina were indicative of a pseudopregnant status. In Case 2, the rat had been maintained under abnormal hormonal conditions, and no evidence of any pseudopregnant-like status was found. These results suggest, thus, that the appearance of EG cells is evidence of a reactive pathological condition in the uteri of aged virgin rats, although the precise pathogenesis and biological significance of EG cells remain to be determined.