ACTIVE-TRANSPORT PROPERTIES OF PORCINE CHOROID-PLEXUS CELLS IN CULTURE

We have investigated the transport properties of cultured porcine chor oid plexus cells grown on permeable membranes and in serum-free medium . Withdrawal of serum yielded cell cultures with permeabilities low en ough to establish and maintain a pH-gradient between the two compartme nts of the filter system and to allow apical fluid secretion. This bec ame possible because of ten-fold increased electrical resistance of 17 00 Omega cm(2) in the absence of serum. These plexus epithelial cells transported phenol red, fluorescein, riboflavin and penicillin G from the apical to the basolateral side. K-M values and v(max) were determi ned and come close to in vivo values. Competitive inhibition with prob enicid showed that the organic anion transporter is involved. Riboflav in transport however was not completely inhibited and did not respond quantitatively to the stilben derivate SITS that blocks the Cl-/HCO3- exchanger. We assume that an additional transport system exists for ri boflavin. Ascorbic acid and myo-inositol were transported from the bas olateral to the apical side in vitro which strongly resembles the in v ivo transport from the blood to the cerebrospinal fluid. Again the exp erimental in vitro K-M values come close to the in vivo values. The es tablished epithelial cell culture model thus closely mimics the blood- CSF-barrier and may be a useful tool to further elucidate transport to and from the brain. (C) 1998 Elsevier Science B.V. All rights reserve d.