Abstract
Contrast-enhanced magnetic resonance imaging (CE-MRI) is a valuable technique for the diagnosis of liver diseases. As gadocoletic acid trisodium salt (B22956/1), a new contrast agent showing high biliary excretion, may be potentially advantageous in hepatobiliary imaging, the aim of the study was to investigate the molecular mechanisms of hepatic transport of the B22956 ion in a cellular model of hepatic tumor. B22956 ion uptake was measured in tumoral (HepG2) and nontumoral (Chang liver) hepatic cell lines. Absolute quantitative real-time reverse transcriptase (RT)-polymerase chain reaction (PCR) analyses, using cloned PCR products as standards, were performed on total RNA of both cell lines and normal liver to evaluate the transcription of 12 transport genes: SLCO1A2, SLCO2B1, SLCO1B1, SLCO3A1, SLCO4A1, SLCO1B3, SLC22A7, SLC22A8, SLC22A1, SLC10A1, SLC15A1, and SLC15A2. B22956 transport was more efficient in Chang liver than in HepG2 cells and was inhibited by cholecystokinin-8, a specific substrate of OATP1B3. Real-time RT-PCR analyses revealed different transcription profiles in the tumoral and nontumoral cell lines. Compared with normal liver, the expression of SLCO1B1, SLCO3A1, and SLCO1B3 was greatly repressed in HepG2 cells, whereas SLCO2B1, SLC22A7, and SLC22A8 expression was either maintained or increased. On the contrary, in Chang liver cells, SLC22A7 and SLC22A8 genes were undetectable, whereas the expression of SLCO3A1, SLCO4A1, and SLCO1B3 was similar to normal liver. Transport studies and gene expression analyses indicated that B22956 ion is a good substrate to the liver-specific OATP1B3, reported to be poorly expressed or absent in human liver tumors. Therefore, B22956 may be helpful in detecting hepatic neoplastic lesions by CE-MRI.
Footnotes
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This work was supported by grants from Ministero dell'Istruzione, Università e Ricerca (FIST 2002/359Ric to C.T.), an Erasmus fellowship (to A.L.), Fondazione Cassa di Risparmio di Trieste (FCRT-01); Fondo Studio Fegato-ONLUS, and career development grants from Bracco Imaging S.p.A. (to C.F. and L.P.
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Part of this work was presented at the Federation of European Biochemical Societies Congress and International Union of Biochemistry and Molecular Biology; 2005 July 2–7; Budapest, Hungary. Faculty of Pharmacy, Charles University in Prague, Heyrovského, Hradec Králové, Czech Republic.
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Article, publication date, and citation information can be found at http://jpet.aspetjournals.org.
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doi:10.1124/jpet.106.106591.
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ABBREVIATIONS: MRI, magnetic resonance imaging; GD, BOPTA, gadobenate dimeglumine; Gd-EOB-DTPA, gadoxetic acid disodium; B22956/1, gadocoletic acid trisodium salt, trisodium [(3β,5β,12α)-3-[[(4S)-4-[bis[2-[bis[(carboxy-κO)methyl]amino-κN]ethyl]amino-κN]-4-(carboxy-κO)-1-oxybutyl]amino]-12-hydroxycholan-24-oato(6-)] gadolinate (3-); MRP, multidrug resistance related protein; OATP, organic anion-transporting polypeptide; RT, reverse transcriptase; PCR, polymerase chain reaction; CCK-8, cholecystokinin octapeptide; BSP, bromosulfophthalein; OAT, organic anion transporter; NTCP, sodium-dependent taurocholate cotransporting polypeptide.
- Received April 20, 2006.
- Accepted August 7, 2006.
- The American Society for Pharmacology and Experimental Therapeutics
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