Blood pressure is linked to salt intake and modulated by the angiotensinogen gene in normotensive and hypertensive elderly subjects.
OBJECTIVE
To evaluate salt sensitivity in elderly subjects with different forms of hypertension and controls and to investigate any modulation by genotype


METHODS
Randomized, double-blinded, placebo-controlled latin-square


METHODS
Tertiary referral hospital


METHODS
Community subjects (n = 46) aged > or = 60 years classified as isolated systolic hypertension [ISH; systolic blood pressure (SBP) > or = 160, diastolic blood pressure (DBP) < 90 mmHg, n = 19], diastolic +/- systolic hypertension (SDH; DBP > or = 90 mmHg, n = 10) and normotension (SBP < 160, DBP < 90 mmHg, n = 17).


METHODS
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.


METHODS
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 +/- standard error (SE) of change from baseline in SBP 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 SBP 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 SBP (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.
Johnson
A G
AG
Queensland University Department of Medicine, Princess Alexandra Hospital, Brisbane, Australia. Tony-G-Johnson@sbphrd.com
Nguyen
T V
TV
Davis
D
D
D000368:Aged; D000808:Angiotensinogen / Q000235:genetics*; D001794:Blood Pressure / Q000187:drug effects* / Q000235:genetics* / Q000502:physiology; D003971:Diastole; D004039:Diet, Sodium-Restricted; D004311:Double-Blind Method; D005838:Genotype; D006801:Humans; D006973:Hypertension / Q000209:etiology* / Q000235:genetics / Q000503:physiopathology*; D008875:Middle Aged; D007703:Peptidyl-Dipeptidase A / Q000235:genetics; D012982:Sodium, Dietary / Q000008:administration & dosage*; D013599:Systole
D012982:Sodium, Dietary; D000808:Angiotensinogen; D007703:Peptidyl-Dipeptidase A