EVIDENCE OF ACTIVE TRANSPORT OF BENZYL-14C-PENICILLIN FROM CEREBROSPINAL FLUID TO BLOOD

Data presented supports the hypothesis that benzylpenicillin is transported actively from the cerebrospinal fluid (CSF) to blood. Benzylpenicillin is capable of moving against a concentration gradient, undergoes self‐saturation indicative of a transfer maximum. and is competitively inhibited by p‐aminohippuric acid and probenecid. The locus of this transport mechanism appears to be the choroid plexus. It further appears that active movement of penicillin from CSF to blood may add to the difficulty of obtaining therapeutic concentrations of this antibiotic in the CNS. Data presented also support the concept that the cerebrospinal fluid functions as an escape channel for polar metabolites of neuronal metabolism and various polar drugs. Once a drug or metabolite enters the CSF from blood or brain by simple diffusion, it may be rapidly removed either by a nonselective bulk flow process via the arachnoid granulations or by an active transport mechanism. Copyright © 1969 Wiley‐Liss, Inc., A Wiley Company