Composite Transport Systems for Iodipamide and Iodohippurate out of the Cerebrospinal Fluid in the Rat

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Abstract
The mechanism for the removal of iodohippurate and iodipamide from the CSF in rats was studied by ventriculo‐cisternal perfusion and by uptake experiments with choroid plexusin vitro. In agreement with finclings in other species excised plexus from the lateral ventricles accumulates131I‐o‐iodohippurate and125I‐iodipamide, and the process is at least partly saturable. Ventriculo‐cisternal perfusions were performed on pentobarbital anesthetized rats with a fluid containing131I‐o‐iodohippurate,125I‐iodipamide and14C‐inulin. A considerable loss of iodohippurate and iodipamide, but not of inulin, from the CSF was observed during the perfusion. When sodium hippurate and/or non‐labelled iodipamide were added in excess to the infusion fluid the loss of labelled iodohippurate and iodipamide was reduced. In concentrations which reduced iodohippurate loss equally, hippurate and iodipamide had different effects on iodipamide loss: hippurate had less effect. This indicates that iodohippurate and iodipamide are removed from the CSF partly by saturable and presumably active transport, and that iodipamide is transported both by the same system as iodohippurate and also by a separate hippurate‐insensitive one. Choroid plexus can be one locus of this transport.