Na(+)-H+ antiporter phenotype, abundance, and phosphorylation of immortalized lymphoblasts from humans with hypertension.
Previous studies have demonstrated an elevated Na(+)-H+ exchanger activity in various cell types from patients with essential hypertension. The phenotype of an increased maximal transport capacity is preserved in Epstein-Barr virus immortalized lymphoblasts from hypertensive patients. The mechanisms underlying this abnormality are unclear. In this study, we used lymphoblasts from hypertensive patients and normotensive control subjects with and without a family history of hypertension to determine (1) Na(+)-H+ exchanger activity using fluorometry with the pH indicator 2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein, (2) Na(+)-H+ exchanger isoform 1 abundance with specific polyclonal antibodies, and (3) Na(+)-H+ exchanger phosphorylation by immunoprecipitation of the 32P-labeled transporter. Na(+)-H+ exchanger activity (in millimoles per liter per minute) measured when pHi was clamped at 6.0 was significantly higher in cells from hypertensive patients (18.8 +/- 0.6, P < .001) and those subjects with a family history of hypertension (16.4 +/- 0.6, P < .001) compared with normotensive control subjects (12.9 +/- 0.6). Exchanger abundance was identical in all three groups of subjects, indicating that increased activity in the hypertensive group was due to an elevated turnover number of the exchanger. Na(+)-H+ exchanger phosphorylation in quiescent cells was significantly elevated in cells from hypertensive patients (1.58 +/- 0.16, P < .001) compared with control subjects (1.00 +/- 0.07), and cells from normotensive subjects with a hypertensive family history showed intermediate values (1.23 +/- 0.14). Identical changes in Na(+)-H+ exchanger function and phosphorylation have been demonstrated in vascular smooth muscle cells from spontaneously hypertensive rats.(ABSTRACT TRUNCATED AT 250 WORDS)
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L L
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Department of Medicine and Therapeutics, Leicester Royal Infirmary, UK.
Sweeney
F P
FP
Siczkowski
M
M
Davies
J E
JE
Quinn
P A
PA
Krolewski
B
B
Krolewski
A S
AS
D000328:Adult; D002478:Cells, Cultured; D005260:Female; D006801:Humans; D006863:Hydrogen-Ion Concentration; D006973:Hypertension / Q000378:metabolism*; D008214:Lymphocytes / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D010641:Phenotype; D010766:Phosphorylation; D017923:Sodium-Hydrogen Exchangers / Q000032:analysis* / Q000378:metabolism
D017923:Sodium-Hydrogen Exchangers