Vascular Permeability in Experimental Brain Tumors

Abstract

Studies of alterations of the blood-brain barrier caused by neoplasms have been non-specific, and examinations of tissues containing vital dyes or radioactive isotopes have indicated only that leakage from blood vessels at some level has presumably occurred in some tumors. To determine accurately the sites of damage to blood vessels of a neoplasm a substance would be needed which would escape through the injured vessel wall and remain localized in the pervascular space. Small particles, as those mentioned above, have traveled through tissues far beyond leaking blood vessels so that detection of their site of escape was not possible in most instances. The method of labeling abnormally permeable blood vessels devised by Majno seemed ideal for such an investigation provided the damage was severe enough to allow particles of 200 A. size to escape. Permeability of the vasculature of methylcholanthrene induced brain tumors was studied in mice by tracer injection of fine C-black of a near-standard particle size of 200 A. After the 1st week of growth vessels of these tumors have shown increasingly abnormal permeability for particles of this size. Such defects have appeared first to the thin-walled veins and venous sinusoids and later have involved capillaries throughout each tumor. Arterial branches were spared.