Cerebrospinal fluid formation and absorption and transport of iodide and sulfate from the spinal subarachnoid space

Numerous studies have demonstrated transport mechanisms within the cerebral ventricles which regulate the concentration of solutes within the cerebrospinal fluid (CSF) in vivo. Furthermore, studies of choroid plexus transport in vitro indicate that ependymal cells play a major role in these active regulatory mechanisms. Unfortunately, less attention has been given to the possibility that such mechanisms may exist in extraventricular compartments such as the spinal subarachnoid space (SSS). Ventriculo-lumbar, ventriculo-cisternal and cisternal-lumbar perfusions were performed in anesthetized cats to study bulk formation and absorption of spinal subarachnoid fluid (SSF), and the clearance of radioiodide and sulfate from the SSS. The results obtained are summarised in Table 4. Finally, the results indicate that non-ependymal tissues or cells are capable of actively transporting iodide from the SSF to blood. The probable locus of this transport mechanism and its relation to the "sink" hypothesis are discussed.