Enhanced Na(+)-H+ exchanger activity and NHE-1 mRNA levels in human lymphocytes during metabolic acidosis

• Published in: The American journal of physiology Vol. 266; no. 2 Pt 1; p. C480
• Main Authors: Quednau, B, Rosskopf, D, Reusch, H P, Luft, F C, Siffert, W
• Format: Journal Article
• Language: English
• Published: United States 01.02.1994
• Subjects: Acidosis - metabolism; Autoradiography; Base Sequence; DNA, Complementary - genetics; Ethidium; Glyceraldehyde-3-Phosphate Dehydrogenases - genetics; Humans; Hydrogen-Ion Concentration; Lymphocytes - metabolism; Male; Molecular Sequence Data; Polymerase Chain Reaction; RNA, Messenger - metabolism; Sodium-Hydrogen Exchangers - genetics; Sodium-Hydrogen Exchangers - metabolism; Staining and Labeling
• ISSN: 0002-9513
• DOI: 10.1152/ajpcell.1994.266.2.c480

It has recently been demonstrated that uremic metabolic acidosis and experimental metabolic acidosis caused by ingestion of ammonium chloride coincide with increased Na(+)-H+ exchanger (NHE-1) activity in human blood cells. In the present study, we investigated whether an increased level of NHE-1 specific mRNA in human lymphocytes during the course of an experimental metabolic acidosis could explain the enhanced transport activity during metabolic acidosis. Six healthy individuals were studied before and after 5 days of taking 15 g of ammonium chloride daily. Plasma pH and bicarbonate decreased significantly, from 7.42 +/- 0.027 to 7.28 +/- 0.05 and from 26.7 +/- 2.0 to 15.6 +/- 2.9 mM, respectively. Basal cytosolic pH (pHi) and Na(+)-H+ exchange activity were measured in lymphocytes loaded with the fluorescent pHi indicator 2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein. Basal pHi remained unchanged during metabolic acidosis (7.03 +/- 0.07 vs. 7.03 +/- 0.06). Ethylisopropylamiloride-sensitive pHi recovery increased from 0.046 +/- 0.007 to 0.076 +/- 0.012 dpHi/min (P < 0.0001). The transcript level of NHE-1 mRNA was measured by reverse-transcription polymerase chain reaction in comparison with a constitutively expressed reference gene (glyceraldehyde-3-phosphate dehydrogenase). NHE-1 mRNA in human lymphocytes increased 1.5-fold in metabolic acidosis. These data suggest that the increased Na(+)-H+ exchange activity in metabolic acidosis may be caused by de novo synthesis of antiport protein.