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Received for publication January 19, 2006.
Revised May 2, 2006.
Accepted for publication May 3, 2006.
The ability of the kidney and small intestine to synthesize and subsequently eliminate dinitrophenyl-S-glutathione (DNP-SG), a substrate for the multidrug resistance-associated proteins (Mrps), was assessed in bile duct ligated rats 1, 7 and 14 days after surgery, using an in vivo perfused jejunum model with simultaneous urine collection. A single i.v. dose of 30 µmol/Kg b.w. of 1-chloro-2,4-dinitrobenzene (CDNB) was administered and its glutathione conjugate DNP-SG and dinitrophenyl cysteinyl glycine (DNP-CG) derivative, which is the result of
-glutamyl-transferase action on DNP-SG, were determined in urine and intestinal perfusate by HPLC. Intestinal excretion of these metabolites was unchanged at day 1, and decreased at days 7 and 14 (-39% and -33%, respectively) after surgery with respect to Shams. In contrast, renal excretion was increased by 114%, 150% and 128% at days 1, 7 and 14. Western blot studies revealed decreased levels of apical Mrp2 in liver and jejunum but increased levels in renal cortex from BDL animals, these changes being maximal between days 7 and 14. Assessment of expression of basolateral Mrp3 at day 14 post-surgery indicated preserved levels in renal cortex, duodenum, jejunum, distal ileum and colon. Analysis of expression of glutathione-S-transferases alpha, mu and pi, as well as activity towards CDNB, indicates that formation of DNP-SG was impaired in liver, preserved in intestine and increased in renal cortex. In conclusion, increased renal tubular conversion of CDNB to DNP-SG followed by subsequent Mrp2-mediated secretion into urine partially compensates for altered liver function in experimental obstructive cholestasis.
Key words:
ABC transporters, glutathione, glutathione transferases, hepatobiliary transport, intestinal transport, liver disease, MRP, renal elimination, toxicity
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