Cerebrospinal fluid iodide

In vitro preparations of rabbit choroid plexus accumulated I 131 to a concentration 20–30 times the media. The accumulation was temperature dependent and was blocked by metabolic inhibitors. It could also be saturated with iodide, and was inhibited by perchlorate, fluoroborate, and related anions. In vivo the low 4-hr steady state concentration (1.6% of plasma) of trace doses of I 131 in the rabbit cerebrospinal fluid was increased (to 40% of plasma) by the systemic administration of iodide or perchlorate. The results resembled qualitatively those obtained in the vitreous and aqueous humors of the same animals and suggested an active transport of iodide out of the cerebrospinal fluid, much as postulated previously for ocular fluids.