DIFFERENTIAL EXPRESSION OF NA-ANTIPORTER MESSENGER-RNA IN BILIARY EPITHELIAL-CELLS AND IN HEPATOCYTES(,H+)

Background/Aims: Amiloride inhibitable Na+,H+-exchange has recently be en identified and characterized in rat biliary epithelial cells where its activity at low intracellular pH is significantly higher than in h epatocytes. Methods: Northern blot and reverse transcription-polymeras e chain reaction were used to study the expression of the different Na +,H+-antiporter isoforms in isolated biliary epithelial cells and hepa tocytes. Results: The present study demonstrates for the first time th e expression of Na+,H+-antiporter isoform 1 mRNA in rat biliary epithe lial cells. Moreover, steady-state levels of this message were several -fold higher in biliary epithelial cells than in hepatocytes, In addit ion, the expression of Na+,H+-antiporter isoform 2 in bile duct epithe lial cell but not hepatocytes could be demonstrated by reverse transcr iption-polymerase chain reaction. Conclusions: The higher expression o f Na+,H+-antiporter isoform 1 mRNA may indicate a higher rate of synth esis and therefore a higher Na+,H+-exchange activity in biliary epithe lial cells than in hepatocytes and is entirely compatible with the res ults of the previous functional studies.