Attenuated release of atrial natriuretic factor due to sodium loading in salt-sensitive essential hypertension

Forty-one patients with essential hypertension were classified as salt-sensitive (SS) or non-salt-sensitive (NSS) from the changes in mean blood pressure (MBP) with alterations in sodium intake from 35 mmol (low-sodium) to 250 mmol/day (high-sodium). Whereas there was no difference in plasma levels of atrial natriuretic factor (ANF) on a normal-sodium diet (120 mmol) between the 2 groups, the degree of increase in the plasma ANF level between the low- and high-sodium intake was significantly greater in NSS than in SS (p less than 0.001). In addition, the urinary sodium excretion on a high-sodium diet was smaller in SS than in NSS. There was a significant positive correlation between the plasma ANF and MBP after the high-sodium intake in both SS (r = 0.67, p less than 0.01) and NSS (r = 0.60, p less than 0.01); however, the relation of plasma ANF to MBP shifted apparently to a lower level in SS compared with NSS. These findings not only indicate that there exists a hyporesponsiveness of ANF release by the heart of SS patients in response to high-sodium loading, but also imply that such a response contributes to blood pressure-elevating mechanisms due to sodium loading in this type of human hypertension.