Analysis of MRP1 and MRP3 expression profile in liver and spleen of hyperbilirubinemic rodents

Unconjugated bilirubin (UCB) is produced mostly in the spleen from the turnover of heme. UCB is conjugated by the activity of hepatic UGT1A1enzyme (UDP-glucuronosyltransferase 1A1) and exported into the bile. High serum level of UCB is toxic to cells, and its intracellular accumulation is suggested to be limited by multidrug resistance proteins 1 and 3 (MRP1 and MRP3) that export UCB out of the cells to prevent its toxicity. In this study, the expression profile for MRP1 and MRP3 was analysed by qRT-PCR and Western blot in the liver and the spleen of two animal models of hyperbilirubinemia (β-thalassemic mouse and Gunn rat). The results indicated that MRP1 mRNA and protein expression remained unchanged in the liver and spleen of both animal models. MRP3 mRNA and protein are up-regulated in the spleen of β-thalassemic mouse and liver of Gunn rat. In conclusion, high level of UCB induces only the expression of MRP3 which may indicate its possible role in preventing UCB toxicity