THE EFFECT OF ACUTE RADIATION INJURY ON THE PERMEABILITY AND ULTRASTRUCTURE OF INTRACEREBRAL CAPILLARIES

Abstract

A study was made on the vascular permeability alteration produced in the rat brain 2 to 9 days after a single application of 30 krad of X‐rays. The permeability was assessed by fluorescence and electron microscopy following intravenous injection of Evans blue‐albumin (EBA) and horseradish peroxidase (HP). Both tracers penetrated vascular walls and spread extensively outside the vessels in the irradiated regions. The HP penetrated between separated endothelial cells or through gaps formed by necrotic endothelial cells. The vascular basement membranes and the perivascular astrocytes did not prevent the further diffusion of HP. Lesions of the vascular endothelium are considered to be of crucial importance for the extravasation of proteins in acute radionecrosis of the brain.