Na+-Li+ countertransport and electrolyte composition in erythrocytes of patients with essential hypertension before and after antihypertensive treatment.

The effect of antihypertensive treatment with 6-12 mg of the loop diuretic piretanide over 12 weeks on Na+-Li+ countertransport, and on extra- and intracellular electrolyte composition was studied in 10 previously untreated patients with essential hypertension. These data were compared with 10 sex- and age-matched controls. Blood pressure fell from 180 +/- 18.3/110.5 +/- 9.8 to 154.7 +/- 9.7/92.5 +/- 10.9 mmHg during treatment. Na+-Li+ countertransport was significantly higher in hypertensives (0.36 +/- 0.13 mmol X l-1 rbc X h-1) compared with controls (0.25 +/- 0.05; P less than 0.05). Na+-Li+ countertransport and intracellular electrolyte composition remained unchanged whereas the extracellular potassium concentration fell from 4.28 +/- 0.51 to 3.98 +/- 0.36 mmol/l (P less than 0.05). No increase in the intracellular Na+ content as compared with normotensive controls was found. It is concluded that the intracellular Na+ concentration is not a marker for essential hypertension. The Na+-Li+ countertransport does not seem to be directly related to elevated blood pressure but seems to be a general marker for diseases associated with an increased risk for the development of hypertension.