Expression and localization of Na+/H+ exchanger (NHE) isoforms in nasal mucosa *
The Na+ /H +exchanger (NHE) is an important regulator for intracellular pH, cell volume, and transepithelial Na+ transport. The NHE has a tightly coupled1:1stoichiometry for exchange of Na+and H + . The exchange reaction is driven by the transmembrane chemical gradients forNa+. The presence of multiple forms of the exchanger has been demonstrated by the recent cloning of seven NHEs, NHE1, 2, 3, 4, 5, 6, and 7. Physiological studies have shown the NHE to be a carrier protein regulating airway surface liquid (ASL) pH and the intracellular pH in airway epithelial cells. To date, the localization of the NHE isoforms in airway is not known. The present study was undertaken to examine the expression and distribution of NHE1-4 isoforms in guinea pig and human nasal mucosa. We used the reverse transcription-polymerase chain reaction to assess the expression of NHE1-4 isoforms. Although NHE 2 and 4 isoform mRNAs could not be detected in guinea pig nasal mucosa tissue, NHE1 and 3 mRNAs were predominant. We used in situ hybridization to examine their localization in guinea pig and human nasal mucosa. NHE 1 isoform mRNA was distributed in nasal epithelial cells, as was NHE 3 isoform mRNA, but the latter's expression was lower than that of NHE 1. NHE 3 isoform mRNA also distributed in the lamina propria. Although NHE 1 was housekeeping, it became clear that it is especially mostly expressed into a nasal epithelial cells. These findings suggest that NHE 1 and 3 regulate ASL pH and the intracellular pH in airway epithelial cells. (Accepted on February 26, 2002) kawasaki Igakkaishi 28 (2) : 83-93, 2002
