Estimation of granulocyte and lymphocyte potassium in normal subjects and in patients treated with diuretics because of cardiovascular disease: a methodological study.

A method is described for measuring the potassium content in leukocytes using Percoll (R) density gradient centrifugation. Ninety subjects between 21 and 92 years formed the reference population. The magnesium content in leukocytes could not be estimated because of interaction between the ion and the Percoll (R) media. Sex, age, leukocytosis because of infection, physical stress, venous stasis did not interfere with the analysis. The potassium content was calculated per cell and per g-1 of DNA. The granulocyte potassium content was (median (range)) 37.4 (25.8-75.0) fmol/cell-1 or 2.9 (1.5-9.8) mmol g-1 DNA. The lymphocyte potassium content was 45.9 (26.4-69.6) fmol cell-1 or 3.3 (1.5-5.0) mmol g-1 DNA. The coefficient of variation (less than 10%) was not reduced by using cell DNA instead of cell number as reference. The interindividual variation was high, making the test unfit for clinical use. The leukocyte potassium content was not decreased in patients with acute myocardial infarction nor in patients treated with diuretics and potassium supplements because of cardiovascular disease.