STUDIES ON THE SITE OF MEDIATED TRANSPORT OF CHLORIDE FROM BLOOD INTO CEREBROSPINAL FLUID: EFFECTS OF ACETAZOLAMIDE

— In monkeys we measured the steady‐state concentrations of Cl− in endogenous CSF, in artificial CSF (which had equilibrated with the underlying exposed surface of the cerebral cortex but was not in diffusion equilibrium with endogenous CSF), and in arterial plasma. The ratio of the distribution of Cl− in artificial CSF to that in plasma was consistent with a passive Donnan distribution, whereas that ratio describing Cl− levels in endogenous CSF in comparison to those in plasma clearly exceeded theratio required for a passive, Donnan−type of distribution for Cl−. The kinetic analysis of the efflux of Cl− from blood into endogenous CSF and into artificial CSF (perfused over the exposed surface of the cerebral cortex) indicated that the rate of efflux of Cl− into endogenous CSF which was continuous with ventricular fluid was inhibited by acetazolamide [in confirmation of a similar finding described previously by Maren and Broder (1970)], whereas the rate of efflux of chloride from blood into the artificial CSF perfusate was uninfluenced by pretreatment of animals with acetazolamide. We have discussed the site of mediated (active) transport of chloride from blood into CSF in light of these findings.