Hepatic expression of multidrug resistance protein 2 in biliary atresia

No significant differences in hepatic MRP2 expression level were observed between BA and controls groups. There was no correlation between MRP2 expression and age at time of surgery in BA and control groups. In BA patients, MRP2 expression level in the jaundice and jaundice-free group did not differ significantly (2.0 × 10-4 vs 3.1 × 10-4, p = 0.094). Although the serum level of total bilirubin just before surgery did not correlate with MRP2 expression level (rs = 0.031, p = 0.914), the serum level of total bilirubin measured at 2 weeks (rs = -0.569, p = 0.034) and 4 weeks after surgery (rs = -0.620, p = 0.018) were significantly correlated with MRP2 expression level. Furthermore, MRP2 expression level was inversely correlated with ratio of change in serum total bilirubin level over 4 weeks (rs = -0.676, p = 0.008), which represents the serum bilirubin level measured at 4 weeks after surgery divided by value just before surgery. There was no correlation between expression level of MRP2 and nuclear receptors, such as retinoid × receptor α, farnesoid × receptor, pregnane × receptor, or constitutive androstane receptor.Hepatic MRP2 expression level was associated with postoperative clearance of jaundice in BA patients, at least within 1 month after hepatoportoenterostomy. This finding suggests that not only morphological appearance of the liver tissue but also the biological status of hepatocytes is important for BA pathophysiology.Biliary atresia (BA) is an idiopathic inflammatory obliterative cholangiopathy of neonates, leading to progressive biliary cirrhosis [1]. If performed within the first 3 months of life, hepatoportoenterostomy (Kasai procedure) can cure jaundice in 30% to 80% of patients [2-4]. Postoperative clearance of jaundice is one of the most important factors influencing long-term outcomes of BA patients. A multicenter study of 104 BA patients revealed that patients with total bilirubin level < 2 mg/dl at 3 months after hepatoportoenterostomy had signi