Erythrocyte sodium concentration and 86Rb uptake in weanling Dahl rats

Alterations in Na, K ATPase pump activity as well as erythrocyte (RBC) intracellular sodium concentration (Nai) have been demonstrated in humans and rats with established hypertension. The contribution of hypertension itself to these changes is unclear. Accordingly, we investigated RBC ion transport and plasma ouabain-like factor (OLF) in four- to five-week old normotensive Dahl salt-sensitive (DS) and salt-resistant (DR) rats on low salt diet. Although both strains were normotensive, systolic blood pressure (SBP) of DS (123 +/- 2 mm Hg) was higher than that of DR (116 +/- 1 mm Hg). No interstrain difference was evident in RBC pump activity measured as ouabain-sensitive 86rubidium (86Rb) uptake (DS = 0.277 +/- .030 and DR = 0.271 +/- .029 mumol/10(9)RBC/h) even though RBC Nai was greater in DS than DR (14.9 +/- 2.0 v 10.7 +/- 1.0 mEq/L; P less than 0.05). Plasma OLF was higher in DS than DR (28.9 +/- 4.7 v 16.5 +/- 2.3 pmol/mL; P less than 0.05), but did not correlate with RBC pump activity in either strain. RBC Nai was directly correlated with pump activity in DS (r = 0.84, P less than 0.01) and demonstrated a trend to correlate in DR (r = 0.71, P = 0.07). RBC Nai was also directly correlated with SBP in DR (r = 0.73, P less than 0.05) and DS (r = 0.70, P = 0.05). We conclude that RBC Nai is genetically determined in Dahl rats and is elevated in normotensive DS who are at risk for hypertension development.(ABSTRACT TRUNCATED AT 250 WORDS)