Permeability characteristics of brain adjacent to tumors in rats

The brain immediately surrounding 9L sarcoma and Walker 256 carcinosarcoma was evaluated, using radioactive water, albumin, red blood cells, urea, and sodium to quantitate isotopic exchange and permeability in the brain adjacent to tumor (BAT), normal brain, and, to a lesser extent, tumor. Exchange between blood and BAT for 14C-urea and 22Na averaged 53% of that for comparable regions of normal brain. This reduction in exchange is not explainable by differences in capillary surface area for transcapillary exchange in the BAT. This reduction in capillary permeability in the BAT could be detrimental to the delivery of watersoluble and rapidly binding drugs.