Abnormal erythrocyte sodium leak in a subset of essential hypertensive patients.
We measured the ouabain- and bumetanide-resistant Na+ efflux in Mg2+-sucrose medium (passive Na+ leak) in erythrocytes from 30 normotensive controls and 72 essential hypertensive patients. The mean values (+/- SEM) of the rate constant of Na+ leak (kpNa) were not significantly different between normotensives and hypertensives. Nevertheless, using the 95% confidence limits of the kpNa (in 10(-3).h-1) in the normotensive group as a cut-off point, 7 (9.7%) essential hypertensives exhibited increased values (58.96 +/- 10.12) when compared with the other 65 patients (23.86 +/- 0.74). revealing increased passive Na+ permeability in the former (leak "+" hypertensives). Na+ fluxes depending on the Na+-K+ pump, outward Na+-K+ cotransport, and Na+-Li+ countertransport were also measured in fresh erythrocytes from the same 72 patients. Three of them (4.2%) exhibited decreased values of ouabain-sensitive Na+ efflux and 6 (8.3%) of bumetanide-sensitive Na+ efflux, while 8 patients (11.1%) showed increased values of Li+-stimulated Na+ efflux and, finally, 48 patients (59.7%) did not present any evident abnormality in these Na+ transport systems. No differences were observed between leak "+" hypertensives and the remaining 65 patients when both basal erythrocyte Na+ content and clinical parameters of hypertension were compared. However, Na+ efflux depending on the outward Na+-K+ cotransport was significantly higher in the leak "+" hypertensive subset (299.43 +/- 43.18 vs 181.52 +/- 10.76 mumol.(l cells.h)-1; P = 0.0078), suggesting a compensatory phenomenon. Enhancement of Na+ permeability detected in 3% to 16% of essential hypertensives may be implicated in the pathogenesis of primary hypertension.
De la Sierra
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Department of General Internal Medicine, Hospital Clínico, School of Medicine, University of Barcelona, Spain.
Coca
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Aguilera
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Urbano Márquez
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D000328:Adult; D000368:Aged; D001692:Biological Transport / Q000187:drug effects; D002034:Bumetanide / Q000494:pharmacology; D004912:Erythrocytes / Q000378:metabolism*; D005260:Female; D006801:Humans; D006973:Hypertension / Q000097:blood*; D007473:Ion Channels / Q000187:drug effects; D008297:Male; D008875:Middle Aged; D010042:Ouabain / Q000494:pharmacology; D011188:Potassium / Q000097:blood; D012964:Sodium / Q000097:blood*
D007473:Ion Channels; D002034:Bumetanide; D010042:Ouabain; D012964:Sodium; D011188:Potassium