Autonomic Nervous System and Benign Essential Hypertension in Man

Abstract

The effect of upright posture as a physiological stimulus of the adrenergic nervous system was studied in 56 subjects with benign essential hypertension. The subjects received a controlled-sodium diet. Blood pressure, heart rate, catecholamines, plasma renin activity, and urinary creatinine, sodium, and potassium excretion were measured in the recumbent and upright positions. We found an alteration in the blood pressure response in subjects with benign essential hypertension; the postural increase in the mean blood pressure in normotensive subjects (3.18 ± 1.35 mm Hg) progressively disappeared and was replaced by a postural decrease in subjects with more severe stable hypertension (-6.71 ± 2.42 mm Hg). The hypertensive subjects also lacked the usual increase in urinary excretion of norepinephrine. A significant increase in plasma renin activity associated with a significant decrease in plasma norepinephrine occurred in subjects with labile hypertension with postural tachycardia. Finally, we found a highly significant correlation between the excretion of sodium and potassium in the recumbent position and the retention of both ions in the upright position. KEY WORDSpostural adaptation plasma renin activity urinary dopamine, norepinephrine, and epinephrine plasma norepinephrine orthostatic antinatriuresis renal clearance of norepinephrine• In a previous paper (1), we described the rationale for and the method in which limits between normotension and labile and stable hypertension were determined in recumbent subjects. In the present investigation, these same subjects were exposed to the stimulus of upright posture. This approach was of interest because the reproducible, physiological stimulus of upright posture normally induces activation of hemodynamic and closely related hormonal mechanisms. Hemodynamic studies of subjects with hypertension have shown that the postural stimulus differentiates between subjects who react by an excessive response and those who have an insufficient postural response (2). Hormonal studies have demonstrated a differentiation between subjects who show a

Dopaminergic abnormalities in borderline essential hypertensive patients.

“…Patients were considered to be borderline EH when their blood pressure decreased, off medication, to normotensive values after 4 days of bed rest. 10 They received a diet containing 150 mmol/ day sodium, 100 mmol/day potassium, and 90 g protein. Citrus fruit, cereals, and coffee were excluded for at least 3 days before the test.…”

The Effects of Psychosocial Stress on Urinary, Excretion of Adrenaline and Noradrenaline in 51- to 55- and, 71- to 74-Year-Old Men

“…These results are in accordance with ours for urinary noradrenaline mean percent of increase and blood pressure; they are at variance, however, with the urinary levels of adrenaline and noradrenaline observed in the present study. This emphasizes the discrep ancy existing in aged people between an ob served decrease in urinary catecholamine lev els [12,31,34] and an observed increase in plasma noradrenaline levels in normotensive subjects [47,64], Blood pressure tends to increase with age in industrial populations, and hypertensive subjects have higher nor adrenaline plasma levels than normotensive subjects [36]. However, when noradrenaline levels are corrected for age, hypertensive sub jects have the same levels as control subjects [37,47], Juchmes et al [31] explain this rise of plasma noradrenaline levels by the de crease in glomerular filtration rate occurring with aging [27],…”

The contribution of vasopressin and angiotensin to the maintenance of blood pressure after autonomic blockade.

“…33 This finding is often interpreted as implying sympathetic hyperactivity in hypertension; however, the same result is obtained when other classes of antihypertensive drugs are used. 33 - 34 The results in the present studies also throw considerable doubt on this interpretation, as the fall in BP after autonomic blockade is determined not only by removal of sympathetic tone but also by the relative activation of the renin-angiotensin system and AVP. Our results clearly demonstrate the importance of AVP and the renin-angiotensin system in compensating for the loss of autonomic neural control of BP.…”