Red Blood Cell Li + -Na⁺ Countertransport, Na ⁺ -K⁺ Cotransport, and the Hemodynamics of Hypertension

Red blood cell Li⁺-Na⁺ countertransport and Na⁺-K⁺ cotransport activities, home blood pressure, invasive systemic hemodynamics, and limb venous compliance were measured in 65 white men (23 normotensive, 22 borderline hypertensive, and 20 mild essential hypertensive subjects). Li⁺-Na⁺ countertransport activity was positively and significantly correlated with subject-determined home systolic blood pressure (r = 0.31, p < 0.02) and with directly measured systolic (r = 0.29, p < 0.02) and diastolic (r = 0.27, p < 0.03) blood pressures in the hemodynamic laboratory, independent of potential confounding variables. Analysis of the hemodynamic determinants of blood pressure revealed a significant positive correlation of countertransport with vascular resistance (r = 0.30, p < 0.02) but not with cardiac output or cardiac index. High red blood cell Na⁺-K⁺ cotransport activity was not independently associated with hypertension or with a characteristic hemodynamic pattern but was related to decreased venous compliance. Red blood cell Li + -Na ⁺ countertransport deserves further study as a marker for the genetic substrate of human essential hypertension. Red cell Na⁺-K⁺ cotransport may be altered secondarily by factors related to high blood pressure and seems to be a valid marker for abnormalities of the venous system in hypertension.