Differential expression of Na+,H+-antiporter mRNA in biliary epithelial cells and in hepatocytes

Background/Aims: Amiloride inhibitable Na+,H+- exchange has recently been identified and characterized in rat biliary epithelial cells where its activity at low intracellular pH is significantly higher than in hepatocytes. Methods: Northern blot and reserve transcription-polymerase chain reaction were used to study the expression of the different Na+,H+-antiporter isoforms in isolated biliary epithelial cells and hepatocytes. Results: The present study demonstrates for the first time the expression of Na+,H+-antiporter isoform 1 mRNA in rat biliary epithelial cells. Moreover, steady-state levels of this message were several-fold higher in biliary epithelial cells than in hepatocytes. In addition, the expression of Na+,H+-antiporter isoform 2 in bile duct epithelial cell but not hepatocytes could be demonstrated by reverse transcription-polymerase chain reaction. Conclusions: The higher expression of Na+,H+-antiporter isoform 1 mRNA may indicate a higher rate of synthesis and therefore a higher Na+,H+-exchange activity in biliary epithelial cells than in hepatocytes and is entirely compatible with the results of the previous functional studies.