Red blood cell K+ could be a marker of K+ changes in other cells involved in blood pressure regulation

The aim of this study is to determine whether red blood cell K+ content (RBCKi) is associated with blood pressure levels and, if so, could RBCKi be a marker of potassium changes in other cells involved in blood pressure regulation. The study was performed on 50 untreated hypertensives, 32 of their offspring and 50 age- and sex-matched controls. Systolic (SBP) and diastolic (DBP) blood pressures, height, weight, plasma, urine and red blood cell electrolytes were measured in all subjects. RBCKi was significantly lower in hypertensives than in offspring of hypertensives and normotensive controls. Offspring of hypertensives had significantly lower RBCKi than normotensive controls. Plasma K+ was significantly lower both in hypertensives and offspring of hypertensives when compared to normotensive controls. A significant negative correlation was found in hypertensives between RBCKi and DBP (r=−0.27, P=0.04) and in offspring of hyper-tensives between RBCKi and DBP (r=−0.43, P=0.02). A significant correlation was found in hypertensives between RBCKi and plasma K+ (r=0.3, P=0.02). A positive correlation with borderline significance was found in hypertensives between RBCKi and ionized Ca2+ (r=0.2, P=0.1). In conclusion, our results support the hypothesis that RBCKi is associated with blood pressure levels and that the measurement of RBCKi levels may represent a biochemical marker for K+ changes in other cells involved in blood pressure regulation. Further studies are necessary to explain the exact mechanisms of reduced RBCKi levels in hypertensive patients and their offspring.