Salt Intake and Hypertension

To confirm our previous study and to observe the effect of long-term anti-hypertensive therapy, we studied 89 patients with essential hypertension under the following 3 different dietary salt balance conditions: Phase I (control diet); daily dietary salt ingestion of 10 g for more than 10 days, Phase II (low-salt diet); 2 g of salt for 4 days plus oral administration of 120 mg of furosemide on the morning of the first day and Phase III (high-salt diet); 22 g of salt for 4 days. The patients were divided into three groups according to blood pressure response to sodium: Group I (salt-sensitive); mean blood pressure (MBP) in Phase II decreased more than 10% of that in Phase I or that in Phase III exceeded by 10% or more than that in phase II, Group II (paradoxically salt-sensitive); MBP in Phase II increased more than that in Phase I, and the remaining Group III (non-salt-sensitive). Thirty-four, 18 and 37 patients could be classed into Groups I, II and III, respectively. Cardiovascular profiles of the patients on admission did not differ among the three groups except for hematocrit. As compared with MBP on admission, the fall of MBP in Phase I was greater in Group II than in Group I. Percent changes of pulse rate, body weight and hematocrit showed a tendency toward a greater fluctuation in Group I than in Group II, in all three phases. Plasma renin activity and plasma aldosterone concentration among the three groups did not differ significantly in any phase. However, pressure-renin index showed a significant difference between Groups I and II. Antihypertensive drugs given to Group I were all diuretics alone or diuretics plus other(s), whereas in Group II there were no patients taking diuretics alone. These results indicate that volume factor(s) contribute to high blood pressure in Group I and vasoconstrictive factor(s) such as renin-angiotensin and sympathetic nervous systems in Group II.