No abstract

One function of the vertebrate choroid plexus (CP) is removal of potentially toxic metabolites and xenobiotics from cerebrospinal fluid (CSF) to blood for subsequent excretion in urine and bile. We have used confocal microscopy and quantitative image analysis to follow transport of the large organic anion fluorescein-methotrexate (FL-MTX) from bath (CSF side) to blood vessels in intact rat CP and found concentrative transport from CSF to blood. With 2 microM FL-MTX in the bath, steady-state fluorescence in the subepithelium and vascular spaces exceeded bath levels by 5- to 10-fold, but fluorescence in epithelial cells was below bath levels. FL-MTX accumulation in subepithelium and vascular spaces was reduced by NaCN, Na removal, and by other organic anions, e.g., MTX, probenecid, and estrone sulfate. Increasing medium K 10-fold had no effect. None of these treatments affected cellular accumulation. However, two observations indicated that apical FL-MTX uptake was indeed mediated: first, cellular accumulation was a saturable function of medium substrate concentration; and second, digoxin and MK-571 reduced FL-MTX accumulation in the subepithelial/vascular spaces but also increased cellular accumulation severalfold. In the presence of digoxin and MK-571, cellular accumulation was concentrative, specific, and Na dependent. Thus transepithelial FL-MTX transport involved the following two mediated steps: Na-dependent uptake at the apical membrane and electroneutral efflux at the basolateral membrane, possibly on Oatp2 and Mrp1.

Our results suggest that Atx is an effective treatment in adult ADHD. It reduces ADHD core and associated emotional symptoms and increases self-esteem and quality of life. AEs were consistent with those reported in other studies in adult ADHD.

Background: The goal of the present study was to develop an in vitro choroid plexus (CP) epithelial cell culture model for studying transport of protein-mediated drug secretion from blood to cerebrospinal fluid (CSF) and vice versa.

The vertebrate choroid plexus removes potentially toxic metabolites and xenobiotics from cerebrospinal fluid (CSF) to blood for subsequent excretion in urine and bile. We used confocal microscopy and quantitative image analysis to characterize the mechanisms driving transport of the large organic anion, fluorescein-methotrexate (FL-MTX), from bath (CSF-side) to blood vessels in intact lateral choroid plexus from dogfish shark, Squalus acanthias, an evolutionarily ancient vertebrate. With 2 microM FL-MTX in the bath, steady-state fluorescence in the subepithelium/vascular space exceeded bath levels by 5- to 10-fold, and fluorescence in the epithelial cells was slightly below bath levels. FL-MTX accumulation in both tissue compartments was reduced by NaCN, Na removal, and ouabain, but not by a 10-fold increase in medium K. Certain organic anions, e.g., probenecid, MTX, and taurocholate, reduced FL-MTX accumulation in both tissue compartments; p-aminohippurate and estrone sulfate reduced subepithelial/vascular accumulation, but not cellular accumulation. At low concentrations, digoxin, leukotriene C4, and MK-571 reduced fluorescence in the subepithelium/vascular space while increasing cellular fluorescence, indicating preferential inhibition of efflux over uptake. In the presence of 10 microM digoxin (reduced efflux, enhanced cellular accumulation), cellular FL-MTX accumulation was specific, concentrative, and Na dependent. Thus transepithelial FL-MTX transport involved the following two carrier-mediated steps: electroneutral, Na-dependent uptake at the apical membrane and electroneutral efflux at the basolateral membrane. Finally, FL-MTX accumulation in both tissue compartments was reduced by phorbol ester and increased by forskolin, indicating antagonistic modulation by protein kinase C and protein kinase A.