The effect of sodium depletion and potassium supplementation on vasopressin, renin and catecholamines in hypertensive men

Sex differences in essential hypertension

A group of 41-year-old hypertensive men (n = 35, blood pressure (BP) 149.9 +/- 2.1/98.9 +/- 1.1 mmHg, mean +/- SEM) who had never received treatment for their condition were compared with hypertensive women of the same age (n = 18, BP 155.9 +/- 4.3/98.1 +/- 1.6 mmHg) with comparable body mass index (BMI, 25.9 +/- 0.5 vs. 24.9 +/- 4.5 kg m-2) who, also, had never received treatment. The lipid profile was more atherogenic in the men, with lower HDL cholesterol (1.21 +/- 0.04 vs. 1.38 +/- 0.06 mmol l-1, P = 0.04), higher total cholesterol (6.04 +/- 0.14 vs. 5.54 +/- 0.18 mmol l-1, P = 0.04) and triglycerides (1.80 +/- 0.16 vs. 0.96 +/- 0.10 mmol l-1, P < 0.001). The hypertensive men had higher haemoglobin (P < 0.001) and haematocrit. Plasma catecholamines were inversely related to BMI in the women only (r = -0.52, P < 0.05 for both noradrenaline and adrenaline). Women with BMI above 25 kg m-2 had significantly lower arterial plasma adrenaline and noradrenaline than those with BMI below 25 kg m-2 (28 +/- 5 vs. 78 +/- 16 pg ml-1, P < 0.01 and 101 +/- 17 vs. 206 +/- 33 pg ml-1, P < 0.01 respectively). A negative curvilinear relationship appeared between arterial adrenaline and insulin (r = 0.49, P = 0.05). These results suggest a male propensity for athero-thrombogenic risk factors in otherwise comparable hypertensive subjects. A close relationship between metabolic risk factors within the normal range seems to exist even in hypertensive women. The decreased sympathetic activity at rest in the obese hypertensive women indicates different pathophysiological mechanism for hypertension in lean and obese. Decreased sympathetic activity and thus reduced energy expenditure, promotes a risk for weight gain, and could explain the inverse relationship between insulin and adrenaline.

By how much does dietary salt reduction lower blood pressure? III--Analysis of data from trials of salt reduction

OBJECTIVE

To determine whether the reduction in blood pressure achieved in trials of dietary salt reduction is quantitatively consistent with estimates derived from blood pressure and sodium intake in different populations, and, if so, to estimate the impact of reducing dietary salt on mortality from stroke and ischaemic heart disease.

DESIGN

Analysis of the results of 68 crossover trials and 10 randomised controlled trials of dietary salt reduction.

MAIN OUTCOME MEASURE

Comparison of observed reductions in systolic blood pressure for each trial with predicted values calculated from between population analysis.

RESULTS

In the 45 trials in which salt reduction lasted four weeks or less the observed reductions in blood pressure were less than those predicted, with the difference between observed and predicted reductions being greatest in the trials of shortest duration. In the 33 trials lasting five weeks or longer the predicted reductions in individual trials closely matched a wide range of observed reductions. This applied for all age groups and for people with both high and normal levels of blood pressure. In people aged 50-59 years a reduction in daily sodium intake of 50 mmol (about 3 g of salt), attainable by moderate dietary salt reduction would, after a few weeks, lower systolic blood pressure by an average of 5 mm Hg, and by 7 mm Hg in those with high blood pressure (170 mm Hg); diastolic blood pressure would be lowered by about half as much. It is estimated that such a reduction in salt intake by a whole Western population would reduce the incidence of stroke by 22% and of ischaemic heart disease by 16% [corrected].

CONCLUSIONS

The results from the trials support the estimates from the observational data in the accompanying two papers. The effect of universal moderate dietary salt reduction on mortality from stroke and ischaemic heart disease would be substantial--larger, indeed, than could be achieved by fully implementing recommended policy for treating high blood pressure with drugs. However, reduction also in the amount of salt added to processed foods would lower blood pressure by at least twice as much and prevent some 75,000 [corrected] deaths a year in Britain as well as much disability.

Aging and urinary vasopressin excretion in healthy men

The influence of age on urinary excretion of arginine vasopressin (antidiuretic hormone) was examined in three groups of healthy men, 25 +/- 1 (n = 12), 40 (n = 44) and 50 years of age (n = 28) respectively. Despite increasing plasma vasopressin with progressive age (2.5 +/- 0.6 vs. 3.5 +/- 0.4 vs. 7.4 +/- 1.0 ng/l, respectively) (means +/- SE), urinary excretion of vasopressin turned out similar (6.7 +/- 1.0 vs. 6.8 +/- 0.8 vs. 6.9 +/- 0.6 ng/h). No differences in sodium excretion, serum osmolality and creatinine clearance appeared that could explain these findings. The present results suggest that age-related impairment of renal concentrating capacity is compensated for by increasing circulating plasma vasopressin. Furthermore, differences in tubular handling of the hormone with age may explain the present findings, and may be another compensatory mechanism for decreased urinary concentrating ability.