Biomedical subjects

U Schorr

Publications and source records attributed to U Schorr.

27 records · Page 2Linked to original sources

PubMed1997

Relationship between ambulatory and resting blood pressure responses to dietary salt restriction in normotensive men.

OBJECTIVE: To examine the relationship between changes in resting and ambulatory blood pressures induced by dietary salt restriction in 90 young normotensive men. METHODS: Subjects were given a standardized low-salt diet containing 20 mmol sodium chloride per day for 14 days. To this diet, a daily supplement of 20 tablets of slow sodium (10 mmol NaCl per tablet) or placebo was added in a randomized single-blind cross-over fashion for 7 days. The ambulatory blood pressure was measured on the sixth day and the resting blood pressure was measured on the seventh day of each dietary period. RESULTS: Although salt intake did not affect blood pressure levels in the whole group, the response of the blood pressure was quite variable among individual subjects. Salt-induced changes in resting systolic (r = 0.30, P = 0.006) and mean (r = 0.27, P = 0.014) blood pressures, but not diastolic blood pressure, were correlated positively to changes in daytime ambulatory blood pressure. The changes in resting systolic and mean blood pressures were also correlated significantly to the nocturnal falls in systolic (r = 0.26, P = 0.015) and mean (r = 0.27, P = 0.012) blood pressure levels and heart rate (r = 0.26, P= 0.015) under the high-salt diet. Diet-induced changes in resting mean blood pressure were correlated significantly to the daytime ambulatory blood pressure (r = 0.30, P < 0.005) and the resting heart rate (r = 0.24, P < 0.02) under the high-salt diet. CONCLUSION: Salt-induced changes in resting blood pressure in young normotensive men are correlated positively to changes in ambulatory daytime blood pressure levels as well as to the daytime ambulatory blood pressure and the nocturnal fall in blood pressure under a high-salt diet. These findings suggest that dietary salt-intake restriction can lower both resting and daytime ambulatory blood pressure levels in some normotensive individuals who may be predisposed to the development of hypertension.

Adult↗

PubMed1997

Identification of a renin threshold and its relationship to salt intake in a patient with pure autonomic failure.

Animal studies have demonstrated a threshold below which renin release increases proportionally to a decrease in renal perfusion pressure. Demonstration of a similar mechanism in humans, however, has proved difficult, as any attempt to lower blood pressure below the putative renin threshold results in renin release mediated by reflex activation of the sympathetic nervous system. In this study, we report on our observations in a 71-year-old woman who presented with a 20-year history of faintness and syncope and was diagnosed as having pure autonomic failure. Graded head-up tilting resulted in a stepwise reduction in mean arterial blood pressure to a minimum of 54 mm Hg, with no signs of increased sympathetic activity. A fall in blood pressure below 80 mm Hg resulted in a distinct rise in plasma renin activity, and a similar threshold pressure was observed under both a 50- and a 100-mmol/d sodium chloride diet. Below the threshold, response to changes in perfusion pressure was proportionally greater under the 50-mmol/d diet than under a 100- or 200-mmol/d diet. These observations demonstrate that a pressure threshold for renin release at 10 to 15 mm Hg below ambient blood pressure, as described previously in animal studies, is also present in humans. The significance of this pressure-dependent mechanism of renin release for the long-term regulation of blood pressure and water and mineral balance in humans remains to be determined.

Aged↗

PubMed1996

Effect of sodium chloride- and sodium bicarbonate-rich mineral water on blood pressure and metabolic parameters in elderly normotensive individuals: a randomized double-blind crossover trial.

OBJECTIVE: To examine the effect of sodium chloride- and sodium bicarbonate-rich mineral water on blood pressure and parameters of glucose and lipid metabolism in elderly normotensive individuals. METHODS: We examined 21 healthy men and women aged 60-72 years in a randomized, placebo-controlled, double-blind crossover trial. After reducing dietary salt intake to below 100 mmol/day, study participants were randomly assigned to drink 1.5 l daily of a sodium chloride-rich (sodium 84.5 mmol/l, chloride 63.7 mmol/l, bicarbonate 21.9 mmol/l), a sodium bicarbonate-rich (sodium 39.3 mmol/l, chloride 6.5 mmol/l, bicarbonate 48.8 mmol/l) and a low-sodium (placebo: sodium, chloride and bicarbonate < 0.02 mmol/l) mineral water for 4 weeks each in a three-phase crossover order. Each phase was separated by a 2-week washout period in which the study participants remained on a low-salt diet. Compliance was assessed by biweekly urinary electrolyte excretion and five study participants were excluded from analysis for failing to complete the trial or to fulfil the compliance criteria. RESULTS: Mean arterial blood pressure was significantly lower during the periods of consuming low-sodium -7.0 +/- 7.2 mmHg, P < 0.001) or sodium bicarbonate-rich (-5.7 +/- 6.4 mmHg, P < 0.05) water than at baseline. In contrast, blood pressure during the phase of drinking sodium chloride-rich water was identical to that at baseline. Ambulatory 24 h blood pressure, oral glucose tolerance and plasma lipids were not affected by the different regimens. Urinary calcium excretion was significantly reduced by drinking low-sodium or sodium bicarbonate-rich water but was unchanged under the sodium chloride-rich water. CONCLUSION: Consumption of sodium chloride-rich mineral water can abolish the blood pressure reduction induced by dietary salt restriction in elderly individuals. Sodium bicarbonate-rich mineral water in conjunction with a low-salt diet may have a beneficial effect on calcium homeostasis.

Aged↗

PubMed1996

Salt sensitivity and insulin resistance: Is there a link?

Salt sensitivity is not only found in patients with essential hypertension but also in normotensive individuals. These salt-sensitive normotensives are believed to be genetically predisposed to the development of hypertension. In this paper we present data from our studies in such normotensive salt-sensitive individuals, thereby focusing on the relationship between salt sensitivity and familial history of hypertension and on insulin sensitivity. Salt-sensitivity was associated with a positive familial history of hypertension, a finding that supports the hypothesis that salt sensitivity in normotensive individuals points to a genetic predisposition for the development of hypertension. Also, salt-sensitive subjects displayed a hyperinsulinaemic response to an oral glucose load and a decreased insulin-mediated glucose disposal, as assessed by the insulin suppression test. The latter finding implies that insulin resistance is present in otherwise healthy, hypertension-prone individuals before overt hypertension develops. Assuming that there is a pathophysiological relationship between insulin resistance and salt sensitivity, our findings suggest that early recognition of insulin resistance and the implementation of measures aimed at improving insulin sensitivity could contribute to the prevention of cardiovascular disease in these individuals.

Blood Glucose↗

PubMed1994

Dietary v intravenous salt loading for the assessment of salt sensitivity in normotensive men.

The purpose of this study was to compare the blood pressure response to two commonly used protocols for the assessment of salt sensitivity in normotensive men, involving either the rapid intravenous administration of a saline load followed by diuretic-induced salt depletion, or the more physiologic but time-consuming approach involving dietary salt depletion and repletion. Twenty-two healthy male volunteers (22-35 years old) were given a saline load (2 L of 0.9% NaCl over 4 h, i.v.), and on the following day, a low-salt diet (20 mmol NaCl) and furosemide (3 x 40 mg, po). Resting mean arterial blood pressure (MABP) was assessed after the saline load and on the morning following salt depletion. After a 2-week wash-out period, subjects were given a low-salt diet (20 mmol/day NaCl) for 2 weeks, supplemented by either 220 mmol/day NaCl or placebo for 1 week each. At the end of each week, resting MABP was assessed in the supine subjects. Although MABP changes were quite variable (iv, mean -2.1 mm Hg; range, -9.1 to +5.6; diet, mean -2.0 mm Hg; range, -14.3 to +7.2), there was a significant correlation between the salt-induced changes in MABP (r = 0.56, P < .01) and diastolic blood pressure (r = 0.56, P < .01) between the two protocols. However, in individual subjects, blood pressure response to the intravenous protocol did not uniformly predict the blood pressure response to the dietary protocol.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1993

Effects of sodium salts on plasma renin activity and norepinephrine response to orthostasis in salt-sensitive normotensive subjects.

The blood pressure-raising effect of sodium chloride in salt-sensitive individuals depends on the administration of both sodium and chloride. While sodium chloride is well known to suppress the activity of the renin-angiotensin-aldosterone and the sympathetic nervous system, the effects of nonchloride sodium salts on the response of these systems to physiological stimuli have not been previously studied. We therefore examined the effect of dietary intake of sodium chloride or sodium citrate on the activity of the renin-angiotensin-aldosterone and the sympathetic nervous system during rest and following stimulation by active orthostasis in normotensive salt-sensitive (n = 7) and salt-resistant (n = 8) subjects. The subjects were given a low-salt diet (20 mmol/day) for 3 weeks, to which a supplement of 200 mmol sodium per day, provided as either sodium chloride or sodium citrate, or a placebo, was added for 1 week each. We found that sodium chloride raised blood pressure in the salt-sensitive subjects (P < .005), while sodium citrate did not. Both salts, however, led to a similar suppression of the plasma levels of renin activity, angiotensin II, aldosterone, and norepinephrine (P < .01). Both sodium salts attenuated the renin response to orthostasis in salt-sensitive and salt-resistant individuals (P < .01), but the orthostasis-induced rise in renin activity was significantly smaller in the salt-sensitive than in the salt-resistant group under both sodium salts (P < .05).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1993

Effect of dietary salt restriction on urinary serotonin and 5-hydroxyindoleacetic acid excretion in man.

OBJECTIVE: To determine the effect of dietary salt restriction on urinary excretion of serotonin and its principal metabolite 5-hydroxyindoleacetic acid (5-HIAA) in man. DESIGN: We studied 16 healthy male volunteers (age range 20-28 years) who ate a standard diet containing 20 mmol/day NaCl, to which either 220 mmol/day NaCl or placebo was added as a supplement for 1 week each, according to a randomized, single-blind crossover design. METHODS: Urinary excretion of serotonin, 5-HIAA, noradrenaline and vanillylmandelic acid (VMA) were measured during the low- and high-salt periods using reverse-phase high-performance liquid chromatography. RESULTS: During the low-salt diet, 24-h urinary excretion of serotonin increased by 42%, accompanied by a 52% rise in the excretion of 5-HIAA. Salt restriction also increased noradrenaline excretion by 77% and VMA excretion by 40%. Regression analysis revealed a strong positive relationship between the excretion of serotonin and of noradrenaline (r = 0.84, P < 0.001) and between that of 5-HIAA and of VMA (r = 0.74, P < 0.001). CONCLUSIONS: Salt restriction stimulates the serotonergic system in man. Stimulation of this system, in conjunction with the sympathetic nervous system, may contribute to renal sodium conservation during dietary salt restriction in man.

Adult↗

PubMed1993

Insulin resistance in young salt-sensitive normotensive subjects.

Insulin resistance has been demonstrated in patients with essential hypertension, and insulin-mediated sodium retention is believed to contribute to hypertension in these individuals. Recently, a hyperinsulinemic response to an oral glucose load has been found in salt-sensitive normotensive subjects, suggesting that insulin resistance may be present in these hypertension-prone individuals before the development of hypertension. In the present study, we examined the relation between insulin sensitivity and blood pressure response to salt intake in young, lean normotensive subjects on a high and a low salt diet. Insulin sensitivity was estimated by the "insulin suppression test," i.e., by measuring the plasma glucose and insulin concentrations achieved during a 180-minute infusion of somatostatin, insulin, and glucose in 18 healthy male volunteers (age, 21-28 years) given a standardized low salt diet (20 mmol/day) for 2 weeks, supplemented by either 220 mmol of NaCl per day or placebo in a single-blind randomized order for 1 week each. We defined salt sensitivity as a significant decrease in mean arterial blood pressure (> 3 mm Hg [p < 0.05]) measured for 60 minutes at 1-minute intervals on the low salt diet. By this definition, seven of the 18 subjects were salt sensitive. Although insulin infusion resulted in similar plasma insulin levels (approximately 50 milliunits/L) in both groups, concomitant glucose infusion resulted in plasma glucose levels that were more than 50% higher in the salt-sensitive than in the salt-resistant group (p < 0.005 by two-way analysis of variance).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1993

Renal acid-base excretion in normotensive salt-sensitive humans.

Reduced extracellular pH and bicarbonate levels recently have been reported in normotensive salt-sensitive subjects. To assess the possible role of altered renal acid-base handling in the perturbation of acid-base status in these individuals, we measured the renal acid-base excretion after an acute oral administration of either an alkali or acid load in normotensive salt-sensitive and salt-resistant men. Twenty-four young (22 to 29 years old), healthy male volunteers were placed on a low-salt diet (20 mmol NaCl per day) for 2 weeks with either 220 mmol NaCl or placebo added to the low-salt diet for 1 week each in a randomized single-blind crossover order. Salt sensitivity was defined as a significant drop in mean arterial pressure (> 3 mm Hg, mean of 60 readings taken on the seventh day of each diet, P < .05) during the low-salt diet. On the fifth and seventh days of each week, subjects were given an oral load of either sodium citrate (0.7 mmol/kg) or ammonium chloride (2.2 mmol/kg), respectively, in a randomized order, and arterial and urinary acid-base status was assessed at baseline and followed for 8 hours thereafter. According to the above definition, 13 subjects were considered salt sensitive. During the high-salt diet, mean arterial pressure was higher in the salt-sensitive than in the salt-resistant group (P < .01). Cumulative urinary bicarbonate excretion after the administration of sodium citrate was lower in the salt-sensitive than in the salt-resistant subjects during both the low-salt (46%, P < .001) and high-salt (32%, P < .01) diets.(ABSTRACT TRUNCATED AT 250 WORDS)

Acid-Base Equilibrium↗