Univalent Cation Fluxes in Human Erythrocytes from Individuals with Low or Normal Sodium Intake

Background: High salt intake is a risk factor for essential hypertension in man. There is evidence that, in hypertension, intracellular sodium content and univalent cation transport across erythrocyte membranes are changed. It has been proposed that a low-sodium diet has an antihypertensive effect; this may be related to changes in cation fluxes across plasma membranes.

Methods: Sodium and potassium fluxes and the composition of fatty acids were studied in the erythrocytes of people who had eaten a low-sodium vegan diet for many years (n = 9) and in those of controls who had consumed a mixed diet (n = 11) to investigate the dependence of these variables on dietary factors. Both systolic and diastolic blood pressures were lower in vegans than in controls.

Results: The passive permeability to sodium (P <0.05), Na⁺,K⁺ cotransport (P < 0.001) and the intracellular content of exchangeable sodium (P = 0.076) were decreased in the erythrocytes of those who had consumed the low-sodium diet compared with the controls. The activity of the Na⁺-K⁺ pump, Na⁺-H+ exchange and the passive permeability to potassium were unaltered. Swelling-induced K⁺,Cl^– cotransport was increased in the erythrocytes of those who had eaten the low-sodium vegan diet compared with controls (P <0.01). The proportion of linoleic acid was increased (P <0.01) at the expense of eicosapentaenoic and docosahexaenoic acids (P < 0.001) in the erythrocyte membranes of the vegans.

Conclusion: Our results show that levels of intracellular sodium and Na⁺,K⁺ cotransport activity, which increase in patients with hypertension, decreased in those consuming a low-sodium vegan diet. This suggests that the risk of essential hypertension was diminished in the vegan participants, confirming our observation that systolic and diastolic blood pressures were lower in the strict vegans than in the controls.