Blood pressure is linked to salt intake and modulated by the angiotensinogen gene in normotensive and hypertensive elderly subjects

Objectives To evaluate salt sensitivity in elderly subjects with different forms of hypertension and controls and to investigate any modulation by genotype Design Randomized, double-blinded, placebo-controlled latin-square Setting Tertiary referral hospital Participants Community subjects (n = 46) aged greater than or equal to 60 years classified as isolated systolic hypertension [ISH; systolic blood pressure (SBP)greater than or equal to 160, diastolic blood pressure (DBP)< 90 mmHg, n =191, diastolic a systolic hypertension (SDH; DBP greater than or equal to 90 mmHg, n =10)and normotension (SBP < 160, DBP < 90 mmHg, n = 17). Intervention: Four 14 day treatments, 50, 100, 200 and 300 mmol/day of sodium chloride supplementation interspersed with 14 day washout periods on a salt-restricted diet. Main outcome measures The 24 h blood pressure, heart rate, weight, urinary sodium and creatinine clearance measured during baseline, treatment and washout periods and angiotensinogen (AGT) and angiotensin converting enzyme(ACE)genotypes. Results For the entire cohort, the mean a standard error (SE) of change from baseline in SEP for 50, 100, 200 and 300 mmol/day salt was 7.7 +/- 2.4, 12.1 +/- 2.4, 16.6 +/- 3.0, 18.5 +/- 2.6 mmHg, respectively. For DBP, the respective changes were: -0.1 +/- 1.5, 2.4 +/- 1.6, 3.0 +/- 1.5, 5.8 +/- 1.7 mmHg. The increase in SEP among ISH subjects was significantly higher than among subjects in the SDH and normotensive groups (P < 0.05). AGT genotype influenced the effect of salt dose on the change in DBP (P= 0.006) but not SEP (P= 0.7). Conclusions In healthy, older subjects, a linear increase in BP occurred with increasing salt dose, it appeared most pronounced in ISH subjects and could be modulated by AGT genotype.