[The nature of immunohistochemically defined astrocytic cells in rat gliomas]

The nature of astrocytic cells in rat gliomas induced by ethylnitrosourea (ENU) was studied by means of immunohistochemically demonstrating glial fibrillary acidic protein (GFAP), vimentin and beta-subunit of S 100 protein (S 100 beta) on paraffin sections. A special attention was paid to elucidating whether astrocytic cells would be neoplastic or not. The astrocytic cells in tumors were compared with astrocytes in normal rat brains and reactive astrocytes around a stab wound for their morphology, distribution and immunohistochemical characteristics. GFAP positive astrocytic cells in tumors were roughly divided into astrocytic cells and hypertrophic cells that showed morphologically similar appearance to fibrous astrocytes and hypertrophic reactive astrocytes around a stab wound respectively. A few multi-nucleated pleomorphic cells regarded as a kind of hypertrophic cells were also noted in gross tumors. GFAP positive cells were diffusely distributed in early neoplastic proliferations and microtumors, while in gross tumors they tended to be localized at the periphery. The GFAP positive cells were scattered among negative cells of tumors, forming no tumor mass. These findings suggest that the GFAP positive cells show no neoplastic growth, even though histopathologically they exhibit atypism or pleomorphism. The quantitative analysis of GFAP positive cells in tumors indicated more than 8% in most tumors in the white matter, whereas less than 8% in tumors in the gray matter and approximately 5% in gross tumors. The predominance of GFAP positive cells in the white matter was also observed in lesions induced by a stab wound.(ABSTRACT TRUNCATED AT 250 WORDS)