Modulation of Na+ transport systems in Wistar rat erythrocytes by excess dietary Na+ intake.

Plasma Na+, erythrocyte Na+ content and the activity of Na+ transport systems of red cells were measured in Wistar rat fed a normal or high Na+ diet. Net Na+ and K+ fluxes of erythrocytes were also measured in the presence of plasma of rats fed with excess Na+. Na+-K+ cotransport and passive Na+ permeability were increased. Erythrocyte Na+ content was increased after 2 months but not after 8 days of high Na+ intake. No significant difference in plasma Na+ and pump activity could be detected after such a diet. No factor acting in Na+ extrusion was found to be present in plasma of salt loaded rats. These results indicate that Na+ intake may modulate Na+ transport systems, namely passive permeability and Na+-K+ cotransport and that increased Na+ erythrocyte content is not a causative factor.