Sodium-22 uptake in erythrocytes can differentiate between the essential and the secondary hypertensive patient

To determine the Na+/K+ ATPase independent 22Na+ influx into erythrocytes (E) from normal subjects (N), from essential hypertensive patients (EH), and from renal failure patients with secondary hypertension (SH), these studies involved two assay conditions. The erythrocyte suspensions were incubated for 30 minutes at 37 degrees C under two assay conditions: (i) with assay buffers containing 5mEq/L KC1 and varying amounts of NaCl (5 to 100 mEq/L) and (ii) with assay buffers with a range of KC1 (5 to 100 mEq/L) and a constant amount of 5 mEq/L NaCl. The ouabain insensitive percent uptake of 22Na+ in 2 x 10(9) E/mL from N, EH, and SH were 2.77 +/- 0.34, 4.37 +/- 0.83, and 3.72 +/- 0.60, respectively, when the assay media contained equimolar amounts of NaCl and KC1 (5 mEq/L each). The 22Na+ uptake was decreased gradually by progressive increasing concentrations of NaCl or of KC1 in the assay media. When erythrocytes were incubated in assay buffers containing either 50mEq/L NaCl with 5 mEq/L KC1 and 50 mEq/L KC1 with 5 mEq/L NaCl, the relative percentages of 22Na+ uptake in erythrocytes became significantly increased [65% increases in EH, 17% increases in SH over that in N subjects, 41% increases in EH over that of SH subjects; and, 49% increases in EH, 23% increases in SH other than in N subjects, 21% increases in EH over that of SH subjects, respectively]. None of the other assay media showed such differences in the 22Na+ uptake values.(ABSTRACT TRUNCATED AT 250 WORDS)