{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2024,5,17]],"date-time":"2024-05-17T15:38:18Z","timestamp":1715960298400},"reference-count":38,"publisher":"Wiley","issue":"3","license":[{"start":{"date-parts":[[2008,1,2]],"date-time":"2008-01-02T00:00:00Z","timestamp":1199232000000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/onlinelibrary.wiley.com\/termsAndConditions#vor"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Experimental Physiology"],"published-print":{"date-parts":[[2008,3]]},"abstract":"<jats:p>Sheep choroid plexus epithelium expresses equilibrative nucleoside transporters (ENT) 1 and 2 and concentrative nucleoside transporter 2 at the transcript level. This study aimed to explore the kinetics and functional role of these transporters at the basolateral side of the sheep choroid plexus epithelium perfused <jats:italic>in situ<\/jats:italic>. The cellular uptake of [<jats:sup>3<\/jats:sup>H]adenosine and [<jats:sup>3<\/jats:sup>H]uridine was insensitive to 1 \u03bc<jats:sc>m<\/jats:sc> nitrobenzylthioinosine (NBTI), and the uptake of [<jats:sup>3<\/jats:sup>H]adenosine was reduced significantly when 10 \u03bc<jats:sc>m<\/jats:sc> NBTI was present in low\u2010Na<jats:sup>+<\/jats:sup> Ringer solution. This might suggest that ENT2, a transporter sensitive to micromolar NBTI, is functionally active at the basolateral side of the choroid plexus epithelium while ENT1, a transporter sensitive to nanomolar NBTI, is not active. When low\u2010Na<jats:sup>+<\/jats:sup> Ringer solution was used for the <jats:italic>in situ<\/jats:italic> perfusion, the Na<jats:sup>+<\/jats:sup> concentration in the venous effluent decreased to 14 m<jats:sc>m<\/jats:sc>; under these conditions the maximal uptake (<jats:italic>U<\/jats:italic><jats:sub>max<\/jats:sub>) of [<jats:sup>3<\/jats:sup>H]adenosine and [<jats:sup>3<\/jats:sup>H]uridine did not change significantly when compared with the <jats:italic>U<\/jats:italic><jats:sub>max<\/jats:sub> obtained when Ringer solution that contained 145 m<jats:sc>m<\/jats:sc> Na<jats:sup>+<\/jats:sup> was used. Kinetic analysis revealed apparent Michaelis\u2013Menten constants (<jats:italic>K<\/jats:italic><jats:sub>m,app<\/jats:sub>) for cellular uptake of [<jats:sup>3<\/jats:sup>H]adenosine, [<jats:sup>3<\/jats:sup>H]inosine and [<jats:sup>3<\/jats:sup>H]thymidine of 1.2 \u00b1 0.2, 15.7 \u00b1 2.6 and 3.8 \u00b1 0.9 \u03bc<jats:sc>m<\/jats:sc>, respectively. The HPLC and HPLC\u2013fluorometric analysis of the sheep plasma and cerebrospinal fluid revealed nanomolar concentrations of adenosine and thymidine and micromolar levels of inosine and nucleobases. Considering the estimated <jats:italic>K<\/jats:italic><jats:sub>m,app<\/jats:sub> values, it appears that under normal conditions inosine is the more important nucleoside substrate for uptake by the basolateral membrane of the choroid plexus epithelium than other nucleosides.<\/jats:p>","DOI":"10.1113\/expphysiol.2007.040980","type":"journal-article","created":{"date-parts":[[2007,11,27]],"date-time":"2007-11-27T04:59:20Z","timestamp":1196139560000},"page":"325-333","source":"Crossref","is-referenced-by-count":3,"title":["Kinetics of nucleoside uptake by the basolateral side of the sheep choroid plexus epithelium perfused <i>in 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