Abstract
A weak carboxylic acid transport system, probably resident in the choroid plexus, exists in the cerebrospinal fluid (CSF). In the present study, para-aminosalicylic acid (PAS) transport by this system was investigated. Rabbit choroid plexuses were incubated 5 to 60 minutes in artificial CSF containing 14C-PAS and 3H-inulin. Rabbit choroid plexus accumulated PAS linearly to 30 minutes where a tissue to medium ratio of 11.6 was attained. Uptake of PAS could be inhibited by: 1) increasing the PAS concentratioim, 2) omitting oxygen and/or glucose, 3) adding dinitrophenol to the medium, or 4) adding other weak carboxylic acids to the medium. However, uptake was not inhibited by adding choline, sulfate or iodide to the medium. Kinetic analysis revealed that PAS was transported into the choroid plexus by a process satisfying Michaelis-Menton kinetics. A Hofstee traimsformation of the transport values for the saturable component yielded a Kt of 0.087 mM and a Vmax of 35.9 mµmol/ml/min. In vivo, using standard ventriculocisternal perfusion techniques, saturable transport of PAS clearance from CSF to blood was demonstrated. This active transport system from CSF to blood explains the low levels of PAS in the CSF.
Footnotes
- Received December 18, 1972.
- Accepted February 28, 1973.
- © 1973 by The Williams & Wilkins Co.
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THE ACTIVE TRANSPORT OF para-AMINOSALICYLIC ACID FROM THE CEREBROSPINAL FLUID
