Enhanced Na(+)-H+ exchanger activity and NHE-1 mRNA expression in lymphocytes from patients with essential hypertension.
It has been demonstrated that the activity of the sodium-proton exchanger (NHE-1 isoform) is increased in lymphocytes and other blood cells from patients with essential hypertension. In the present study, we investigated whether an increased level of NHE-1-specific mRNA in lymphocytes from patients with essential hypertension would explain the enhanced transport activity. Twenty-two hypertensive patients and 21 normotensive subjects were studied. Basal cytosolic pH was measured by the pH-sensitive fluorescent probe 2',7'-bis(2-carboxyethyl)-5(6)-carboxyfluorescein. Maximal sodium-proton exchange activity was determined by acidifying cell pH and measuring the initial rate of the net sodium-dependent proton efflux driven by an outward proton gradient. The transcript level of NHE-1 was measured by reverse transcription-polymerase chain 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 +/- SEM, P < .001). The maximal activity of the sodium-proton exchanger was higher in hypertensive patients than in normotensive subjects (1262 +/- 100 versus 881 +/- 56 mmol/L cells per hour, P < .01). NHE-1 mRNA was increased in hypertensive patients compared with normotensive subjects (ratio of NHE-1 mRNA to beta-actin mRNA, 0.16 +/- 0.01 versus 0.12 +/- 0.02, P < .05). These data suggest that the increased sodium-proton exchange activity in essential hypertension may be related to the de novo synthesis of exchanger protein.
Garciandia
A
A
Department of Internal Medicine, School of Medicine, University of Navarra, Pamplona, Spain.
López
R
R
Tisaire
J
J
Arrázola
A
A
Fortuño
A
A
Bueno
J
J
Diez
J
J
D000199:Actins / Q000235:genetics; D000328:Adult; D000368:Aged; D001483:Base Sequence; D005260:Female; D006706:Homeostasis; D006801:Humans; D006973:Hypertension / Q000235:genetics / Q000378:metabolism*; D008214:Lymphocytes / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D008969:Molecular Sequence Data; D015345:Oligonucleotide Probes / Q000235:genetics; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000378:metabolism*; D017923:Sodium-Hydrogen Exchangers / Q000235:genetics* / Q000378:metabolism*
D000199:Actins; D015345:Oligonucleotide Probes; D012333:RNA, Messenger; D017923:Sodium-Hydrogen Exchangers; C069139:growth factor-activatable Na-H exchanger NHE-1