The effect of uremia on penicillin flux between blood and cerebrospinal fluid.

The effect of uremia on the choroid plexus system responsible for transport of penicillin from cerebrospinal fluid (CSF) to blood was studied in vitro and in vivo. Uremia was induced in rabbits by injecting toxic doses of cephaloridine or by obstructing urine flow. Three days after the induction of uremia, isolated choroid plexuses from normal rabbits were unable to concentrate penicillin 14C normally when incubated in either CSF or ultrafiltrates of plasma from uremic rabbits. In vivo, a decrease in the disappearance of penicillin 14C from CSF was observed in uremic rabbits. However, the choroid plexus transport system for penicillin was only partially and reversibly depressed in uremia. The increased CSF levels of penicillin uremia are due to: decreased excretion of penicillin by the kidney, depression of active efflux of penicillin from the CSF, and decreased plasma binding of penicillin.