Differences in Microvasculature between Ethylnitrosourea-induced Brain Tumor and Transplanted 9L Cell Brain Tumor in the Rat

The microvasculature of ethylnitrosourea (ENU)-induced brain tumors and transplanted 9L cell brain tumors were studied in ultrathin sections and by the freeze fracture replica method. The vessels in ENU-induced tumors were similar to human glioma vessels in that they had endothelial tight junctions and increased pinocytotic vesicles. In the 9L cell tumors, the vessels lacked endothelial tight junctions and had fenestrated endothelium. Macroscopically, Evans blue dye penetrated the 9L cell tumors but not the ENU-induced tumors. Judging from the ultrastructure of the microvessels, the ENU-induced tumor appears more suitable as a human glioma model