STUDIES ON THE BLOOD-BRAIN BARRIER WITH RADIOACTIVE PHOSPHORUS

Abstract

RADIOACTIVE isotopes are being used with increasing frequency to localize brain tumors. Either the locally increased permeability of the blood-brain barrier or the active metabolism of the tumors—it is not at present clear which— causes a higher concentration of some isotopes in the tissue of the neoplasm than in the normal brain. The investigations of Hevesy and Hahn¹showed that only a small fraction of radioactive phosphorus (P³²), approximately 0.02% of the total amount, given parenterally, is deposited in the brain. This finding was considered evidence of a slow phosphorus turnover in the central nervous system. Lindberg and I,²working on the theory that the blood-brain barrier plays a decisive role in this phenomenon, injected P³²directly into the cerebrospinal fluid, bypassing the barrier, and found that this isotope would indeed accumulate rapidly in the brain. After such an injection into the cisterna magna (cisterna cerebellomedullaris)