Folate transport by the choroid plexus in vitro.

Reduced folates are transported from blood into cerebrospinal fluid against a concentration gradient. In vitro, folates were transported into and released by isolated rabbit choroid plexuses. The choroid plexus uptake mechanism was specific for folates, energy dependent, and depressed by cold temperatures. In vivo, the choroid plexus may transport folates from blood to cerebrospinal fluid.