Immunohistochemical studies on cellular character of microtumors induced by ethylnitrosourea in the rat brain utilizing anti-Leu 7 and anti-glial fibrillary acidic protein antibodies.

To clarify the chronologic changes in the cellular morphology of ENU-induced rat brain tumors, microtumors in the early stage were examined immunohistochemically in comparison with macrotumors in the advanced stage. The tumor cells composing microtumors were negative for glial fibrillary acidic protein (GFAP), a specific marker of astrocytic cells, and Leu 7, a marker of oligodendrocytes, while cells of macrotumors were positive for either GFAP or Leu 7, showing characteristics of mature glial cells. The results suggested that the small round cells in the early developmental stage, generally thought to resemble mature oligodendrocytes, are not differentiated oligodendrocytes or astrocytes.