Clinical and biochemical factors associated with the blood pressure response to different levels of salt intake in essential hypertension.

The aim of the study was to evaluate several clinical, biochemical, hormonal, intracellular ions and ion transport parameters associated with the BP response to different levels of salt intake in essential hypertensive patients. Fifty essential hypertensive patients were studied during two 7-day periods of low (20 mmol/day) and high (260 mmol/day) salt intakes. The BP response was estimated by 24-h ABPM performed the last day of each period. Baseline characteristics (age, sex, body mass index and left ventricular mass index[LVMI]), as well as biochemical, hormonal, intraplatelet pH and calcium, and maximal rates of eryhtrocyte Na/K pump, Na/K/Cl cotransport, Na/Li countertransport and Na-dependent Cl/HCO3 exchanger were measured at the end of both periods. All these parameters, as well as changes observed between the two periods were correlated with the BP response. The absolute change in 24-h mean blood pressure between low- and high-salt intake correlated with age (r=.30, P=.03), and baseline LVMI (r=.37, p<.01), as well as with plasma renin activity (r=−.32, P=.03) plasma norepinephrine (r=.46, p<.01) and Na/Li countertransport (r=.32, P=.02), all measured at the end of the high-salt period. The change in 24-h mean blood pressure also correlated with the change in plasma norepinephrine (r=.48, p<.01) and the changes in erythrocyte Na/K pump (r=.39, p<.01) Na/K/Cl cotransport (r=.41, p<.01) and Na/Li countertransport (r=.49, p<.01). To account for possible interrelations among variables analyzed, a stepwise multiple linear regression analysis was performed with those variables significantly correlated with the mean blood pressure change. Among them, changes in Na/Li countertransport (adjusted R=.37), changes in Na/K/Cl cotransport (adjusted R=.31) and LVMI measured at baseline (adjusted R=.31) were the only three significant variables associated with the blood pressure response to high-salt intake. In conclusion, an increased left ventricular mass at baseline, and an increase in the maximal rate of erythrocyte Na/Li countertransport and Na/K/Cl cotransport from low- to high-salt intake are associated with a blood pressure elevation from low- to high-salt intake in essential hypertensives.