NHE-1 IS THE SODIUM-HYDROGEN EXCHANGER ISOFORM PRESENT IN ERYTHROID-CELLS

Erythrocyte sodium hydrogen exchanger (NHE) represents one of a limite d number of sodium entry pathway in erythrocytes. At least five NHE is oforms have been identified, differing in tissue specificity, regulato ry characteristics, and pharmacological sensitivities. Although physio logical characteristics of erythrocyte NHE suggest that the widely exp ressed NHE-1 isoform may be present, evidence is not conclusive and do es not exclude the existence of other isoforms. In this study, Norther n blot and reverse transcription-polymerase chain reaction (RT-PCR) an alyses were used to test for five NHE isoforms in erythroid cells. Blo od from patients with sickle cell disease was depleted of white blood cells (WBC) by passage through leukocyte filters and cellulose column. RT-PCR performed on WBC depleted reticulocyte RNA using a NHE-1 prime r set yielded product a of expected size, the sequence of which was id entical to the published human NHE-1 sequence. Northern blot analysis of the reticulocyte RNA using a 1.6 kb probe revealed a message of app roximately 5.0 kb in size. RT-PCR analysis of rat kidney RNA using pri mers specific for NHE isoforms -2, -3, -4 and rat brain RNA using prim er specific for NHE-5 isoform yielded products of expected size? where as WBC depleted RNA under identical conditions yielded no products. Th ese results identify the erythroid isoform of the sodium-hydrogen exch anger as NHE-1. 0005-2736/98/$ - see front matter (C) 1998 Elsevier Sc ience B.V. All rights reserved.