Kinetic aspects of red blood cell sodium transport systems in essential hypertension.

A kinetic study of the interaction of internal sodium with four different erythrocyte sodium transport pathways (ouabain-sensitive Na+-K+ pump, bumetanide-sensitive Na+-K+ cotransport system, Na+-Li+ countertransport, and Na+leak) has facilitated the distinction of the following subgroups of patients with essential hypertension: 1) Leak (+), exhibiting increased passive sodium permeability; 2) Co (-), showing low apparent affinity of the Na+-K+ cotransport system for internal sodium; 3) Counter (+), characterized by increased maximal rates of Na+-Li+ countertransport; and 4) Pump (-), characterized by an abnormally low apparent affinity of the Na+-K+ pump for internal sodium. We present here a new and simple sodium-loading method that allows a simultaneous kinetic study of the above abnormalities. The use of this kinetic assay may improve estimation of the frequencies, clinical features, and other properties of each subgroup of hypertensive patients in different populations.