TRANSPORT OF SULPHATE, THIOSULPHATE AND IODIDE BY CHOROID PLEXUS <i>IN VITRO</i>¹

Abstract

Abstract —Isolated choroid plexuses of rabbits and cats were incubated in artificial cerebrospinal fluid medium containing [ 35 S]sulphate, [ 35 S]thiosulphate or [ 125 I]iodide and combinations thereof. After 1 hr incubation the mean ratio of tissue concentration to medium concentration was 2·46 for [ 35 S]sulphate, 2·39 for [ 35 S]thiosulphate, and 270 for [ 125 I]iodide. Uptake of all three anions was greatly reduced at 0° and by addition of dinitrophenol to the medium. Other inhibitors selectively reduced the uptake of particular anions; non‐radioactive sulphate and thiosulphate reduced both [ 35 S]sulphate and [ 35 S]‐thiosulphate uptake with much less effect on [ 125 I]iodide uptake, while non‐radioactive iodide and thiocyanate greatly reduced [ 125 ]iodide uptake with little or no effect on [ 35 S]sulphate or [ 35 S]thiosulphate uptake. It was concluded: (a) that sulphate and thiosulphate, like iodide, were accumulated by choroid plexus in vitro by active transport; (b) that sulphate and thiosulphate share and compete for a transport mechanism which is separate from the iodide transport mechanism; and (c) that the transport of sulphate out of cerebrospinal fluid demonstrated in vivo could occur at least in part in the choroid plexus.