Sodium sensitivity of blood pressure and baroreceptor reflex function in patients with essential hypertension

In order to define the role of the baroreceptor reflex function in the sodium sensitivity of blood pressure in patients with mild essential hypertension, 25 patients were classified into two groups, salt-sensitive and salt-insensitive, depending on the difference in the averages of the resting systolic blood pressure, taken hourly on the fifth day of 7 days of sodium depletion and on the fifth day of 7 days of repletion. Increases in urinary sodium excretion and body weight and a decrease in haemotocrit during the sodium repletion period were similar in both groups. Baroreceptor reflex function, estimated from the baroreceptor slope and the blood pressure change on a 70 degrees tilting test, was enhanced by the sodium repletion period in the sodium-insensitive group but not in the sodium-sensitive group. These results suggest that sodium sensitivity might be due to differences in the ability of the baroreceptor reflex function to become sensitized during a high sodium intake.