Erythrocyte sodium transport in malignant hypertension

Twenty-three patients with treated malignant hypertension (MH), 23 patients with treated non-malignant hypertension (NMH) and 46 normotensive control subjects were investigated with regard to intraerythrocyte sodium (Na) and potassium (K) levels, as well as transmembrane fluxes of sodium (Na-influx and Na-efflux rate constant). Intraerythrocyte Na and K concentrations were determined by flame photometry. The Na-influx and Na-efflux rate constant were calculated from uptake values for 22Na in vitro. In NMH the Na-influx and Na-efflux rate constant were significantly higher while intraerythrocyte Na and K levels did not differ from the controls. Patients with MH tended to have an elevated intraerythrocyte Na concentration, but an unchanged Na-influx and Na-efflux rate constant relative to controls. The increased rate of erythrocyte membrane transport of Na in treated NMH could be due to a stimulatory effect of antihypertensive treatment on cellular Na transport. Patients with treated MH do not show this effect, and in addition, tend to have an elevated intraerythrocyte Na concentration, which is compatible with the existence of a more pronounced abnormality of cellular ion transport in MH.