Radioactive86Rubidium Influx into Red Blood Cells in Essential Hypertension in Relation to the Plasma Renin Activity

Changes in several mechanisms of sodium transport across the cell membranes are described in essential hypertension. We studied ouabain-sensitive and insensitive 86 Rb + influx into the red blood cells (RBC) of 16 healthy controls and 51 patients with essential hypertension (EH) divided according to their plasma renin activity (PRA) in 3 groups: 11 patients with high PRA (HREH), 18 patients with normal PRA (NREH) and 22 patients with low PRA (LREH). In addition to studying 86 Rb + uptake by patients RBC, we tested also the effect of the patients' sera on 86 Rb + influx into the RBC of healthy subjects. Red blood cells of patients with HREH and NREH had lower ouabain-sensitive 86 Rb + influx in comparison with controls. No significant differences were found between these hypertensive groups. In contrast 86 Rb + uptake by the RBC of LREH patients was always higher than in controls or HREH and NREH. It was chiefly the ouabain-sensitive component that was raised, but some increase in ouabain-insensitive 86 Rb + influx also could be seen. The serum of patients with HREH and NREH, when incubated with RBC of healthy controls, lowered their ouabain-sensitive 86 Rb + influx. The decrease was more pronounced in NREH than in HREH group. Plasma from LREH patients increased both ouabain-sensitive and ouabain-insensitive 86 Rb + influx into the control RBC. These findings indicate that there may be differences in the sodium/potassium transport mechanisms across the cell membrane in various kinds of EH. The possibility to transfer these abnormalities with serum of patients to the RBC from control subjects suggests that changes in 86 Rb + influx in hypertensive patients are caused by a circulating factor or factors.