Experimental gliomas: an autoradiographic study of the endothelial component

Autochthonous gliomas were induced in rats by intracerebral inoculation of avian of avian sarcoma virus and studied by 3H-thymidine autoradiography. Parenchymal glial tumor cells had a 3H-labeling index (LI) of 3.0 to 13.6%. Endothelial cells in tumor blood vessels had an LI of 2.6 to 34.3%, independent of and in most instances higher than the LI of the glial tumor. Endothelial cells of normal blood vessels had an average LI of 0.3%. This study documents the high proliferative rate of the endothelial cells in anaplastic experimental gliomas, and emphasizes the necessity for seeking direct, incontrovertible evidence to determine whether or not the rapidly proliferating endothelial cells are malignant.