ENHANCED NA-H+ EXCHANGER ACTIVITY AND NHE-1 MESSENGER-RNA EXPRESSION IN LYMPHOCYTES FROM PATIENTS WITH ESSENTIAL-HYPERTENSION()

It has been demonstrated that the activity of the sodium-proton exchan ger (NHE-1 isoform) is increased in lymphocytes and other blood cells from patients with essential hypertension. In the present study, we in vestigated whether an increased level of NHE-1-specific mRNA in lympho cytes from patients with essential hypertension would explain the enha nced transport activity. Twenty-two hypertensive patients and 21 normo tensive subjects were studied. Basal cytosolic pH was measured by the pH-sensitive fluorescent probe 2',7'-bis(2-carboxyethyl)-5(6)-carboxyf luorescein. Maximal sodium-proton exchange activity was determined by acidifying cell pH and measuring the initial rate of the net sodium-de pendent proton efflux driven by an outward proton gradient. The transc ript level of NHE-1 was measured by reverse transcription-polymerase c hain reaction in comparison with a constitutively expressed reference gene (beta-actin). Intracellular pH was lower in hypertensive patients than normotensive subjects (7.34+/-0.01 versus 7.39+/-0.01, mean+/-SE M, P<.001). The maximal activity of the sodium-proton exchanger was hi gher in hypertensive patients than in normotensive subjects (1262+/-10 0 versus 851+/-56 mmol/L cells per hour, P<.01). NHE-1 mRNA was increa sed in hypertensive patients compared with normotensive subjects (rati o of NHE-1 mRNA to p-actin mRNA, 0.16+/-0.01 versus 0.12+/-0.02, P<.05 ). These data suggest that the increased sodium-proton exchange activi ty in essential hypertension may be related to the de novo synthesis o f exchanger protein.