Kinetics of Sodium-Lithium Countertransport in Normotensive and Hypertensive Subjects

The kinetic parameters Vmax and Km of erythrocyte sodiumlithium countertransport (Na-Li CT), and the lithium cell to plasma ratio (Li C:P) measured 24 h after a 1-g oral dose of Li2CO3, were determined in 14 normotensive (NT) and 14 untreated mild hypertensive (HT) maies matched for age and weight. Li C:P and Na-Li CT were strongly correlated (r = −0.73), p < 0.001), confirming the validity of Li C:P as an in vivo index of Na-Li CT. No differences in Li C:P (NT0.27 ± 0.07; HT0.23 ± 0.06), Na-Li CT (NT0.39 ± 0.10 mmol/L/h; HT0.43 ± 0.10 mmol/L/h), Kmax (NT0.58 ± 0.16 mmol/L/h; HT0.68 ± 0.20 mmol/L/h), or Km (NT1.5 ± 0.4 mmol/L; HT1.6 ± 0.9 mmol/L) were found between NT and HT. Our data do not support the marker concept of erythrocyte Na-Li CT in human hypertension.