Putrescine diffusion in cat brain and capillary permeability in rat brain: Relation to CSF putrescine levels in brain tumor patients

Cerebrospinal fluid (CSF) putrescine (Pu) levels are extremely useful measures of active tumor growth in patients harboring medulloblastoma but not in patients harboring most supratentorial malignant gliomas. This study was designed to determine the diffusion coefficient (D) for Pu in cat brain and the capillary permeability coefficient (P_c) in rat brain to explain the failure of supratentorial gliomas to manifest a consistent increase in CSF Pu with progressive tumor growth. The P_c for Pu was found to be greater than the P_c for urea, while the apparent brain D for Pu was lower than that for urea. This implies that Pu crosses capillaries and enters cells more rapidly than urea, which would reduce the amount of Pu that might ultimately reach the CSF by diffusion from tumor. These data explain why CSF levels of Pu are correlated best in medulloblastoms—generally located adjacent to the CSF pathways—and why levels are correlated least in malignant supratentorial gliomas—usually located within the brain hemispheres, from which diffusion to the ventricles and into the CSF would be difficult.