Fluo-cAMP is transported by multidrug resistance-associated protein isoform 4 in rat choroid plexus.
The choroid plexuses (CP) are responsible for transport of micronutrients into brain and clearance of toxic compounds, in addition to its barrier function and production of CSF. Multidrug resistance-associated protein (Mrp) 4 is one transport protein highly expressed in CP tissue and is characterized as a versatile pump for toxicants and signalling molecules. Aim of the study was to determine transport characteristics of a fluorescent cAMP analog in rat CP and to define whether fluo-cAMP can be used for analyses of function, substrate/inhibitor specificity and regulation of Mrp4. Confocal imaging was used to analyze transport mechanisms in absence and presence of various modulators of organic anion transport in freshly isolated and functionally intact CP. Fluo-cAMP transport was saturable, selective, concentrative and metabolism-dependent, following an active two-step mechanism composed of apical uptake into epithelial cells and basolateral efflux. Uptake included a Na(+) -dependent and a Na(+) -independent component and was inhibited by estrone sulfate, taurocholate and sildenafil indicating involvement of organic anion transporting polypeptide Oatp1a5. Efflux was composed of an indirect Na(+) -dependent component and a component inhibitable by, for example, the MRP4 substrates/inhibitors, sulindac sulfide and 4-(2-aminoethyl) benzenesulfonyl fluoride. Therefore, fluo-cAMP can be used as fluorescent model compound for studying involvement of Mrp4 in signalling pathways and neuroprotection in CP.
Reichel
Valeska
V
Institute of Pharmacy and Molecular Biotechnology, University of Heidelberg, Heidelberg, Germany. reichel@uni-hd.de
Kläs
Juliane
J
Fricker
Gert
G
Masereeuw
Rosalinde
R
D000818:Animals; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000494:pharmacology; D001693:Biological Transport, Active; D002831:Choroid Plexus / Q000378:metabolism*; D000242:Cyclic AMP / Q000378:metabolism*; D004970:Estrone / Q000031:analogs & derivatives / Q000494:pharmacology; D005456:Fluorescent Dyes; D008297:Male; D018613:Microscopy, Confocal; D027425:ATP-Binding Cassette, Sub-Family C Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D018696:Neuroprotective Agents / Q000494:pharmacology; D029362:Organic Anion Transporters, Sodium-Independent / Q000378:metabolism; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology; D010879:Piperazines / Q000494:pharmacology; D011188:Potassium / Q000378:metabolism; D011190:Potassium Cyanide / Q000494:pharmacology; D011687:Purines / Q000494:pharmacology; D012313:RNA / Q000096:biosynthesis / Q000302:isolation & purification; D051381:Rats; D017207:Rats, Sprague-Dawley; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D000068677:Sildenafil Citrate; D012964:Sodium / Q000378:metabolism; D013450:Sulfones / Q000494:pharmacology; D013467:Sulindac / Q000494:pharmacology; D013656:Taurocholic Acid / Q000494:pharmacology
D000894:Anti-Inflammatory Agents, Non-Steroidal; D000242:Cyclic AMP; D004970:Estrone; D005456:Fluorescent Dyes; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D018696:Neuroprotective Agents; D029362:Organic Anion Transporters, Sodium-Independent; D010726:Phosphodiesterase Inhibitors; D010879:Piperazines; D011188:Potassium; D011190:Potassium Cyanide; D011687:Purines; D012313:RNA; D000068677:Sildenafil Citrate; D012964:Sodium; D013450:Sulfones; D013467:Sulindac; D013656:Taurocholic Acid; C489542:Abcc4 protein, rat; C421102:Slco1a1 protein, rat; C017296:estrone sulfate