Kinetic analysis of erythrocyte Na+-K+ pump and cotransport in essential hypertension

M. L. Tuck, D. B. Corry, M. Maxwell, N. Stern

Research output: Contribution to journalArticlepeer-review

Abstract

Alterations in red blood cell (RBC) Na+-K+ pump and Na+-K+ cotransport have been described in essential hypertension. We evaluated Na+-K+ pump and cotransport in 30 hypertensive and 26 normotensive subjects subdivided by race and family history of hypertension using an improved method to examine the kinetics of Na and K effluxes. RBCs were Na-loaded by the nystatin method to five different levels of internal Na with pump determined as ouabain-sensitive Na efflux and cotransport as furosemide-sensitive Na and K efflux. Two kinetic parameters were determined for both transport systems: the apparent affinity for Na (K0.5) and the velocity of efflux at saturating internal Na concentration (V(max)). Mean intracellular Na content in fresh RBCs (mmol/L cells) was higher in black hypertensive (12.6 ± 1.8 mmol/L cells) and normotensive subjects (10.9 ± 1.2 mmol/L cells) than in white hypertensive (8.7 ± 1.0 mmol/L cells) or normotensive subjects (8.5 ± 0.8 mmol/L cells). The V(max) and K0.5 for pump were not significantly different between study groups. The V(max) for cotransport was elevated in white hypertensive compared with normotensive subjects, but the K0.5 values were similar. Black normotensive and hypertensive subjects displayed a lower V(max) and increased K0.5 for cotransport compared with the white groups. A family history of hypertension had no influence on cotransport kinetics in blacks but did predict white normotensive and hypertensive subjects with low cotransport. The reduction in intracellular Na affinity for cotransport in black subjects may explain their higher intracellular Na in fresh RBCs. The wide range of cotransport V(max) with normal K0.5 in white hypertensive subjects suggests an abnormality in cotransport activity in this population that differs from that in blacks. This study also demonstrates that the RBC pump, as evaluated by cation flux methodology, functions normally over a wide range of intracellular Na in the hypertensive population.

Original languageEnglish
Pages (from-to)204-211
Number of pages8
JournalHypertension
Volume10
Issue number2
DOIs
StatePublished - 1987
Externally publishedYes

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