Renin suppressibility and blood pressure response during acute sodium loading in patients with essential hypertension

Sequential changes in renin-aldosterone secretions and blood pressure (BP) response during acute sodium (Na) loading were studied in 50 patients with essential hypertension (EH) and nine normotensive volunteers. Following an infusion of 2 L of isotonic saline at a rate of 500 mL/h, plasma renin activity (PRA) and the plasma aldosterone concentration (PAC) were similarly suppressed, while sodium excretion appreciably increased in hypertensive as well as normotensive subjects. When patients were divided into two subgroups according to the extent of renin suppression, 26 were classified as adequate responders with the proportion of decrement of PRA at the end of the infusion exceeding 50% of the baseline values, while 24 were inadequate responders with a decrement of less than 50%. The extent of renin suppression was consistently greater in adequate responders than in inadequate responders throughout the course of infusion. Adequate responders also had a higher pre-saline PRA and attained a smaller post-saline natriuretic response than inadequate responders. Although the mean BP in both subgroups remained stable at all periods, inadequate responders had a minor but significantly higher percent of increment of MBP at the end of the infusion than adequate responders (3.6 +/- 2.0 vs -1.7 +/- 1.4%, p < 0.05). These results suggest that renin suppressibility during acute Na loading may be either linked with maintenance of BP homeostasis or may merely reflect the sodium-volume status of essential hypertension, with patients with greater suppression of renin being more Na-volume resistant than those with less inhibition.