Evidence for altered vascular reactivity in sodium-sensitive young subjects with borderline hypertension

To assess mechanisms associated with the pressor effects of a high sodium diet in susceptible individuals, the hemodynamic and hormonal effects of sodium depletion and repletion were studied in 33 normal subjects and 30 subjects with borderline hypertension. The hypertensive group had significantly higher mean arterial pressure, weight, hematocrit, and upright plasma renin activity. Forearm hemodynamics were measured during periods of ad lib diet, 10 mEq, and 200 mEq sodium diet. The fall in forearm resistance during reactive hyperemia was inversely related to mean arterial pressure at rest (R = .400, p less than .005) and rose significantly in hypertensive subjects during salt depletion, 39 +/- 3.6 to 61 +/- 6.1 mmHg/ml/min/100 g (p less than .05). Sodium sensitivity in either normotensive or borderline hypertensive subjects was defined as an increase in mean blood pressure of more than 5% when sodium repleted. The individuals who were sodium sensitive had a higher forearm vascular resistance during sodium depletion than those who were sodium resistant, 67 +/- 10.5 versus 45 +/- 4.1 mm/ml/min/100 g (p less than .03). We conclude that young individuals with borderline hypertension already have alterations in vascular reactivity. This trait is shared by normotensive individuals whose blood pressure rises in response to sodium.     

Disparate cardiovascular effects of obesity and arterial hypertension

Since obesity and essential hypertension frequently coexist, a study was designed to analyze some of their cardiovascular effects. Twenty-eight obese patients, half of whom were normotensive and half with established hypertension, were matched for mean arterial pressure with 28 corresponding lean subjects. Systemic and renal hemodynamics, intravascular volume, plasma renin activity, and circulating catecholamine levels were measured. Obese patients had increased cardiac output (p less than 0.001), stroke volume (p less than 0.001), central blood volume (p less than 0.02), plasma and total blood volume (p less than 0.01), and decreased total peripheral resistance (p less than 0.001). In contrast, cardiac output, central blood volume, and stroke volume of hypertensive patients were normal, but they had increased total peripheral (p less than 0.001) and renal vascular resistance (p less than 0.001) and a contracted intravascular volume. Left ventricular stroke work was elevated to a similar level in obesity (p less than 0.001) and hypertension (p less than 0.02), but the increase was caused by an expanded stroke volume in the former and by an increase in systolic pressure in the latter. It is concluded that the disparate effects of obesity and hypertension on total peripheral resistance and intravascular volume counteract and may even offset each other. Thus, obesity may mitigate the effects of chronically elevated total peripheral resistance (and therefore end-organ damage) in essential hypertension. Since both entities affect the heart through different mechanisms, their presence in the same patient results in a double burden to the left ventricle, thereby gently enhancing the long-term risk of congestive failure.     

Haemodynamic contributions to post-exercise hypotension in young adults with hypertension and rapid resting heart rates.

The haemodynamic effects of 45 min of treadmill exercise (at 70% of resting heart rate reserve) were determined in 5 young adults with hypertension and rapid resting heart rates (greater than 90 beats/min in clinic) and were compared with those of 5 age-matched normotensive subjects. Blood pressure was lower after exercise in the hypertensive, but not the normotensive subjects. Mean cardiac output before exercise was similar in the two groups, and fell from 6.8 +/- 0.6 before to 5.4 +/- 0.6 l/min 60 min after exercise in the hypertensive group (P less than 0.01). Total peripheral resistance tended to be higher at this time. Neither variable was affected by prior exercise in the normotensive group. The depressor effects of prior exercise on mean arterial pressure (-8.6 +/- 1.0 vs. -1.4 +/- 2.5 mmHg; P less than 0.04) and cardiac output (-1.4 +/- 0.3 vs. -0.1 +/- 0.1 l/min; P less than 0.005) and the increase in total peripheral resistance (+3.0 +/- 1.2 vs. 0.0 +/- 1.0 Units; P less than 0.05) were greater in the hypertensive group. Thus, the post-exercise hypotension in this selected group of young hypertensive subjects with rapid resting heart rates was mediated by a decrease in cardiac output and stroke volume disproportionate to the fall in blood pressure, suggesting sustained compromise of their cardiac performance after acute exercise.     

Plasma prolactin, renin and catecholamines in young normotensive and borderline hypertensive subjects

It has been reported that patients with essential hypertension have high plasma prolactin levels and suggested that reduced central dopaminergic activity may be a factor in the pathogenesis of essential hypertension. This study examines the influence of posture on plasma prolactin, plasma catecholamines, plasma renin activity, blood pressure and heart rate in 24 patients with borderline hypertension (age 19 +/- 1 years) and 20 normotensive subjects matched for age and body mass index. Supine plasma prolactin levels were similar in both groups [borderline hypertension, 11.3 +/- 0.7 ng/ml; normotensive, 10.7 +/- 0.8 ng/ml (mean +/- s.e.m.)] and no increase in plasma prolactin was observed after 10 min standing in both groups. Normotensive and borderline hypertensive subjects had similar values for supine and upright plasma renin activity and plasma norepinephrine. There were no significant correlations between supine plasma prolactin and supine blood pressure, supine plasma renin activity or plasma norepinephrine when data from both normotensive and borderline hypertensive subjects were combined. These results may provide indirect evidence against the occurrence of reduced central dopaminergic activity in borderline hypertension.     

Insulin resistance and blood pressure in young black men

Insulin resistance, independent of obesity or non-insulin-dependent diabetes mellitus, has been demonstrated to be associated with high blood pressure. To determine if insulin resistance could be an antecedent to hypertension in a high-risk population, we studied normotensive (112 +/- 12/70 +/- 10 mm Hg) and borderline hypertensive (135 +/- 8/85 +/- 5 mm Hg) lean young black men (22-26 years old) with the euglycemic hyperinsulinemic clamp technique. All subjects had clinically normal oral glucose tolerance. Body mass index and percent adipose mass were the same in both groups. Fasting plasma insulin concentration was significantly higher in the borderline hypertensive group (p less than 0.01). Insulin-directed exogenous glucose metabolism at the same degree of steady-state hyperinsulinemia was significantly lower in the borderline hypertensive group (5.98 +/- 2.22 versus 8.22 +/- 1.96 mg/kg/min; p less than 0.01). For the total population, a significant inverse correlation existed between the glucose infusion rate and systolic blood pressure (p less than 0.01). These data indicate that there is a relation between insulin-mediated glucose uptake and blood pressure. Furthermore, in this high-risk population insulin resistance may precede the onset of established essential hypertension.     

Essential hypertension in black and white subjects. Hemodynamic findings and fluid volume state.

Systemic hemodynamics (cardiac output, intraarterial pressure, total peripheral resistance) and intravascular volume (plasma volume and red cell mass) were measured in a population of 126 black and white patients, 51 with borderline hypertension and 75 with established essential hypertension. The findings were compared with those in 29 age-matched normotensive control subjects of both races. The white patients with established hypertension demonstrated a faster heart rate than the black patients (less than 0.05); this difference was more pronounced during upright tilt (p less than 0.02). No significant difference in cardiac index, total peripheral resistance, plasma volume or total blood volume was found between the two racial populations. Cardiac index correlated directly with plasma and total blood volume in black patients (r = 0.32, p less than 0.05) and white patients (r = 0.35, p less than 0.001) as well as in the whole study population (r = 0.36, p less than 0.001). The regression lines were similar in the two races. Further, a negative correlation was observed between the total peripheral resistance and plasma volume (r = -0.31, p less than 0.001) or total blood volume (r = -0.34, p less than 0.001), and it was similar in both races (blacks r = -0.48, p less than 0.01; whites r = -0.25, p less than 0.05). Age correlated significantly with total peripheral resistance in the white patients (r = 0.35, p less than 0.001) and in the total study population (r = 0.28, p less than 0.001). We conclude that, for every given age or level of arterial pressure, systemic hemodynamics are similar for the black and white patients with essential hypertension. These data, therefore, do not support the clinical impression that basic pathophysiology and hypertensive vascular disease are different in the black patient with essential hypertension.     

Nocturnal continuous measurement of blood pressure in sleep apnea syndromes. Comparison between normotensive and hypertensive patients

Sleep apnea syndrome and systemic hypertension are frequently associated but their causal relationship is unclear. We compared the oscillations of systemic blood pressure and heart rate during polysomnography in 8 normotensive subjects (2 females) and 5 hypertensive (supine awake blood pressure: 165 +/- 7/96 +/- 5 mmHg) without treatment. Their ages (normotensive: 52.1 +/- 11.0 yrs, hypertensive: 51.2 +/- 6.4 yrs) and body mass indices (32.6 +/- 9.6 kg/m2 vs 33.2 +/- 5.2 kg/m2 respectively) were not statistically different. Systemic blood pressure was continuously monitored by a non invasive digital plethysmography (Finapres). Both groups had similar respiratory events indices (normotensive: 45.2 +/- 18.1/hr, hypertensive: 48.4 +/- 20.5/hr) and minimal oxygen saturations (79.4 +/- 9.1% vs 82.4 +/- 7.0% respectively). During apneas in slow-wave sleep were observed the minimal values for systolic and diastolic pressures which were significantly higher in hypertensive than in normotensive (138.2 +/- 9.6/83.2 +/- 16.1 mmHg vs 105.9 +/- 11.1/60.5 +/- 10.9 mmHg respectively). During resumption of ventilation maximal blood values were recorded which were also higher in hypertensive than in normotensive (185.0 +/- 13.8/113.2 +/- 21.5 mmHg vs 155.9 +/- 19.8/88.7 +/- 17.1 mmHg respectively) (p less than 0.05). Although absolute variations of blood pressure were similar, relative changes in systolic pressure were significantly higher in normotensive (p less than 0.05). Maximal heart rate was 76.8 +/- 6.2 bpm in normotensive and 76.6 +/- 3.9 bpm in hypertensive during resumption of ventilation.(ABSTRACT TRUNCATED AT 250 WORDS)     

Relation of Age to Left Ventricular Structure, Function, and Systemic Hemodynamics in Normotensive and Hypertensive Employed Adults

To determine the effect of age on left ventricular status and systemic hemodynamics, we evaluated by echocardiogram older (age at or above 60 years, n equals 148) and younger (age is less than 60 years, n equals 472) employed adults. Using World Health Organization criteria, the population was divided into the following blood pressure strata: normotensive (n equals 142), borderline hypertensive (n equals 194), and sustained hypertensive (n equals 284). Older subjects were compared to younger subjects in each blood pressure stratum. Older subjects with borderline hypertension and sustained hypertension had a higher systolic blood pressure and wider pulse pressure than younger individuals. Older subjects with borderline hypertension had higher left ventricular mass index (106.7?+/-28.7 vs 93.9?+/-22.4, P equals 0.03), and greater wall thicknesses and relative wall thicknesses than younger subjects. Older borderline hypertensive patients had greater left ventricular wall thicknesses and mass, but closely resembled both age groups of sustained hypertensive patients in this regard. Older and younger individuals with borderline hypertension had similar mean cardiac outputs, stroke volumes, and peripheral resistances. In contrast, older patients with sustained hypertension had a lower stroke volume, stroke volume index, cardiac output, cardiac index, and fractional shortening, and a higher total peripheral resistance than their younger counterparts. There were no significant relations between age and any echocardiographic measurement in normotensive subjects. Borderline hypertensive individuals exhibited weak relationships between age and left ventricular wall thicknesses (r equals 0.17; 23) and left ventricular internal dimensions (r equals -0.19 and -0.21). Very weak negative relationships were identified between age and cardiac output for both hypertensive groups. In conclusion, increasing age had relatively little effect on cardiac status in either normotensive or sustained hypertensive employed adults, but was associated with greater left ventricular hypertrophy among individuals with borderline hypertension according to the World Health Organization classification. These results are consistent with the independent value of age and left ventricular mass as predictors of hypertensive complications, but also suggest that under some circumstances, greater age or longer exposure to hypertension may magnify the target-organ effects at a given degree of blood pressure elevation.     

Cardiovascular and renal function in normotensive and hypertensive patients with compensated cirrhosis: effects of posture

BACKGROUND/AIMS: The aim of this study was to evaluate cardiovascular and renal function in patients with compensated cirrhosis and essential hypertension in the supine position and in response to standing up. METHODS: Twenty-four patients with compensated cirrhosis (12 with elevated arterial pressure) and 20 healthy volunteers underwent echocardiographic evaluation of left ventricular end-diastolic and stroke volumes, ejection fraction, cardiac index, arterial pressure, peripheral resistance, creatinine clearance and sodium excretion in both the supine and the standing position. RESULTS: When supine, only normotensive patients had a hyperdynamic circulation, with increased left ventricular end-diastolic and stroke volumes, cardiac index, and ejection fraction, and reduced peripheral resistance. Creatinine clearance and sodium excretion were comparable in patients and controls. Standing induced a decrease in end-diastolic volume in all subjects. Healthy volunteers maintained cardiovascular homeostasis by increasing ejection fraction and heart rate, while both normotensive and hypertensive cirrhotic patients experienced a fall in stroke volume and cardiac index, despite a marked activation of the renin-aldosterone and sympathetic nervous system. Creatinine clearance decreased only in normotensive patients, who experienced the greatest reduction in sodium excretion. CONCLUSIONS: Compensated cirrhotic patients with arterial hypertension had no evidence of hyperdynamic circulation. Like their normotensive counterparts, hypertensive patients had an impaired cardiovascular response to the postural challenge, but a lesser degree of renal dysfunction during standing.     

Plasma atrial natriuretic peptide in essential hypertension. Comparison with normotensive subjects and effects of changes in dietary sodium intake

Plasma levels of atrial natriuretic peptide (ANP) in 106 patients with essential hypertension with a supine mean blood pressure (mean +/- SEM) of 128.9 +/- 1.6 mmHg and not on treatment were significantly higher than those in 47 normotensive subjects (supine mean blood pressure 93.9 +/- 1.2 mmHg) with mean values of 17.2 +/- 1.1 and 8.6 +/- 0.6 pg/ml, respectively (P less than 0.001). Similar results were found in a subgroup of 35 hypertensive patients identically matched in terms of age, sex, and race with 35 normotensive subjects. Plasma levels of ANP were correlated significantly with age in normotensive subjects and with age and blood pressure in the hypertensive patients. In 12 hypertensive patients studied on a low (10 mmol sodium/day), on their usual sodium intake (around 120 mmol sodium/24 hr) and on a high (350 mmol sodium/day) intake, plasma ANP increased approximately twofold by the fifth day of the high sodium intake, but there was no significant difference between the plasma levels on their usual sodium intake and those on the fifth day of the low sodium intake. Supine mean blood pressure on the patients' usual sodium intake was 119.3 +/- 2.7 mmHg and was reduced to 110.0 +/- 3 mmHg by the fifth day of the low sodium intake (P less than 0.005). However, there was no significant difference between the blood pressure levels on their usual and high sodium intake (118.3 +/- 3.0 mmHg).(ABSTRACT TRUNCATED AT 250 WORDS)     

Exercise hypertension: its measurement and evaluation

Blood pressure, the central parameter in the diagnosis of arterial hypertension, is subject to a high degree of variability. The dilemma for the evaluating physician is that he has no true value for the resting blood pressure that is both comparable and reproducible. Reproducibility, however, is an essential requirement for all diagnostic procedures in medicine. A standardized ergometric procedure (at workloads of 50 to 100 watts [W]; incremented 10 watts/min; cuff blood pressure measurements) is suitable to obtain comparable, reproducible monitoring of the blood pressure response in both pressure response in both normotensive subjects and hypertensive patients. The blood pressure behavior during and after ergometric exercise was investigated in 552 males in order to clarify if this standardized procedure is suitable for differentiating between normotensive subjects and hypertensive patients. The following normal upper limits for blood pressure values in men and women between the ages of 20 and 50 years of 200/100 mmHg (mean + 1 SD) at a workload of 100 W as well as 140/90 mmHg in the fifth minute of the recovery phase were obtained. Patients suffering from mild hypertension showed significantly (p less than 0.001) higher blood pressures (213 +/- 22/116 +/- 11 mmHg) at 100 W and after exercise than age-matched normotensives (188 +/- 14/92 +/- 9 mmHg) but significantly (p less than 0.001) lower values than hypertensives with stable hypertension (225 +/- 22/126 +/- 11 mmHg). Moreover, the systolic pressure response to ergometric work was significantly (p less than 0.05 to p less than 0.01) influenced by age. Using the normal upper limits for blood pressure during and after ergometry, the ergometric procedure revealed that 50% of the patients with borderline hypertension at rest could be classified as hypertensives. Their blood pressure response at 100 W (216 +/- 21/113 +/- 8 mmHg) did not significantly differ from the patients with mild hypertension. In contrast, in the 50% who reacted negatively to ergometric testing, the systolic blood pressure response at 100 W (204 +/- 18 mmHg) was significantly (p less than 0.01) lower than that of those who demonstrated a positive reaction, revealing exactly the same diastolic blood pressure value of 92 mmHg as the normotensives. Follow-up examinations several years (average 3.8 years) subsequently showed that 97% of the ergometric-positive borderline hypertensives developed established hypertension. Thus an early diagnosis of arterial hypertension was achieved years before its established manifestation.(ABSTRACT TRUNCATED AT 400 WORDS)     

Increased stroke volume and aortic stiffness contribute to isolated systolic hypertension in young adults

Isolated systolic hypertension is a common condition in individuals aged older than 60 years. However, isolated systolic hypertension has also been described in young individuals, although the mechanisms are poorly understood. We hypothesized that in young adults, isolated systolic hypertension and essential hypertension have different hemodynamic mechanisms and the aim of this study was to test this hypothesis in a cohort of subjects from The ENIGMA Study. Peripheral and central blood pressure, aortic pulse wave velocity, cardiac output, stroke volume, and peripheral vascular resistance were determined in 1008 subjects, aged 17 to 27 years. Compared with normotensive subjects, those with isolated systolic hypertension had significantly higher peripheral, central, and mean blood pressure, aortic pulse wave velocity, cardiac output, and stroke volume (P<0.001 for all comparisons). However, there were no differences in pulse pressure amplification, heart rate, or peripheral vascular resistance between the two groups. Compared with subjects with essential hypertension, mean pressure, heart rate, and peripheral vascular resistance were all significantly lower in isolated systolic hypertensive subjects, but pulse pressure amplification, aortic pulse wave velocity, cardiac output, and stroke volume were higher (P<0.001 for all comparisons). We have demonstrated that in young adults, isolated systolic hypertension and essential hypertension arise from different hemodynamic mechanisms. Isolated systolic hypertension appears to result from an increased stroke volume and/or aortic stiffness, whereas the major hemodynamic abnormality underlying essential hypertension is an increased peripheral vascular resistance. Long-term follow-up of these individuals is now required to determine whether they are at increased risk compared with age-matched normotensive individuals.     

Decreased water and potassium content in erythrocytes in essential hypertension

The water content in erythrocytes of subjects with borderline or established essential hypertension was measured by using gas-liquid chromatography and was found to be lower than that in normotensive controls (p less than 0.01). The water content in erythrocytes of normal controls (n = 14), borderline hypertensive subjects (n = 18), and established essential hypertensive subjects (n = 23) was (mean +/- SE) 71.0 +/- 0.2%, 69.9 +/- 0.2%, and 69.3 +/- 0.1% (vol/vol), respectively. A definite negative correlation was found between water content of erythrocytes and mean arterial pressure in normotensive and hypertensive subjects (n = 60, r = -0.59, p less than 0.001). Although there was no statistically significant between-group difference in the sodium content, the potassium content of erythrocytes from subjects with essential hypertension was significantly lower than that of normotensive controls (0.205 +/- 0.003 vs 0.222 +/- 0.004 mumol/mg dry red blood cells; p less than 0.01). There was no between-group correlation of sodium and water content in erythrocytes, but the potassium content correlated with the water content (n = 46, r = 0.49, p less than 0.001).     

Decreased exercise capacity in mild essential hypertension: non-invasive indicators of limiting factors.

Available data suggest that exercise capacity is limited in hypertension. The mechanism of this reduced maximal exercise capacity has not been fully elucidated. In this study 22 patients with mild essential hypertension (162 +/- 22 mmHg systolic and 95 +/- 8 mmHg diastolic) and 36 normotensive control subjects (128 +/- 13 mmHg systolic and 80 +/- 7 mmHg diastolic) (P less than 0.01) performed an ergometer test till exhaustion. Body mass index in the two groups did not differ. The maximal oxygen consumption VO2 was lower in the hypertensive group (18 +/- 7 versus 23 +/- 8 ml/kg/min; P less than 0.02) as was the maximal workload (141 +/- 52 vs. 185 +/- 70 Watt; P less than 0.01). Rate pressure product rose only 2.7 fold in hypertensive patients versus 3.5 fold in the control group (P less than 0.001). In hypertensive patients maximal workload decreased with increasing resting systolic blood pressure (P less than 0.05) while in the normotensive subjects maximal workload rose with increasing resting systolic blood pressure (P less than 0.05). In conclusion both high and low blood pressure was associated with a decreased maximal voluntary exercise capacity. Even mild hypertension was accompanied by lower maximal exercise capacity. Hypertensive patients also had a lower maximal VO2 and lower maximal rate pressure product than did normotensive subjects.     

The sympathetic nervous system in hypertension: assessment by blood pressure variability and ganglionic blockade

OBJECTIVE: To determine if the contribution of the sympathetic nervous system to blood pressure could be evidenced by low-frequency oscillations of systolic blood pressure (LF(SBP)), reflecting vascular sympathetic modulation, or by the decrease in blood pressure after autonomic blockade. DESIGN: We studied multiple system atrophy (MSA) patients, in whom supine hypertension is maintained by residual sympathetic tone ('positive controls'); pure autonomic failure (PAF) patients, in whom supine hypertension is largely independent of sympathetic tone ('negative controls'); essential hypertensive patients (HTN) and normotensive subjects (NTN). RESULTS: Supine systolic blood pressure (SBP) was 204 +/- 8, 185 +/- 6, 177 +/- 9 and 130 +/- 4 mmHg in MSA, PAF, HTN and NTN, respectively. LF(SBP) was higher in MSA and HTN (5.7 +/- 1.5 and 5.8 +/- 1.4 mmHg(2) compared to NTN and PAF (3.3 +/- 0.5 and 1.1 +/- 0.5 mmHg(2). Trimethaphan 2-4 mg/min induced complete autonomic blockade and lowered SBP below 125 mmHg in all NTN and all but one MSA (to 111 +/- 3 and 97 +/- 9 mmHg). SBP remained elevated in PAF (164 +/- 7 mmHg). Responses in HTN were variable; SBP decreased below 125 mmHg in three and remained elevated in four patients. The decrease in LF(SBP) correlated with the reduction in SBP, with a steeper slope in MSA and HTN compared to NTN (29.0 +/- 5.5, 8.4 +/- 1.6 and 3.6 +/- 1.2 mmHg/mmH (2), respectively). CONCLUSION: Ganglionic blockade, alone or coupled to LF(SBP), discriminated between human models of sympathetic-dependent (MSA) and independent (PAF) hypertension. This approach may aid in assessing the contribution of the sympathetic nervous system in essential hypertension, in which sympathetic dependence is variably expressed.     

Hemodynamic effects of nicotinic acid infusion in normotensive and hypertensive subjects

Nicotonic acid (NA) infusions are associated with peripheral vasodilation from the generation of vascular prostaglandins with minimal effects on blood pressure (BP) in normotensive subjects. We studied the effects of a NA infusion in 10 hypertensive and 11 normotensive individuals to further characterize systemic hemodynamic responses to NA using pulse waveform analysis. Blood pressure, stroke volume, cardiac output, total peripheral resistance, large and small artery elasticity were determined before and after a 1-h NA infusion. In the normotensives, systolic, diastolic, mean BP, and pulse pressure were not affected by NA. In contrast, the hypertensive subjects experienced a decrease in mean BP from 105 +/- 2 mm Hg to 100 +/- 3 mm Hg (P <.01) accompanied by significant decreases in systolic, diastolic, and pulse pressures. The differential BP response occurred despite comparable increases in heart rate (11% to 13%, P 相似文献   

Hemodynamic characteristics of sodium-sensitive human subjects

Fifty-eight normal subjects and 51 subjects with borderline hypertension underwent microvascular and hemodynamic studies while on an ad libitum diet and during periods of sodium depletion (10 mEq/day) and repletion (200 mEq/day). Hemodynamic measurements included arterial blood pressure, cardiac index, total peripheral resistance, forearm blood flow, vascular resistance, venous compliance, and capillary filtration fraction. Studies of the microcirculation consisted of macrophotography of the bulbar conjunctiva with measurement of anteriolar, venular, and capillary density and diameter. During sodium repletion, cardiac index increased significantly in the normal subjects (2.35 +/- 0.7 vs 2.44 +/- 0.7 L/min/m2; p less than 0.01) and in the borderline hypertensive subjects (2.50 +/- 0.7 vs 2.70 +/- 0.8 L/min/m2; p less than 0.01). However, mean blood pressure rose by more than 5% in only 33 subjects, 13 with normal and 20 with borderline hypertension. When these sodium-sensitive subjects were compared with those whose blood pressure did not rise, the former were found to have significantly higher forearm vascular resistance (32.2 +/- 21 vs 17.9 +/- 12 mm Hg/ml/min/100 g; p less than 0.01), lower forearm blood flow (4.42 +/- 2.7 vs 7.47 +/- 5.0 ml/min/100 g) and lower conjunctival capillary density (3.72 +/- 1.7 vs 5.18 +/- 2.1 [SD] mm/mm2; p less than 0.05). These results indicate that sodium sensitivity in humans is accompanied by elevation of forearm vascular resistance and attenuation of the microcirculation.     

Racial analysis of the volume-renin relationship in human hypertension.

We studied 29 normotensive men (14 black, 15 white) and 36 hypertensive men (27 white, nine black) to examine the association of race with blood pressure, blood volume, and peripheral renin activity (pra). Blood volume was lower in white hypertensive men than in white normotensive men, but was similar in all blacks. When subjects were tested in the supine position, PRA was lower in black normotensive subjects than white normotensive subjects. The PRA did not differ among groups tested in an upright posture, while furosemide-stimulated PRA was lower in hypertensive than normotensive subjects of both races despite lower blood volumes in white hypertensive subjects. Differences of volume and renin measurements appear to reflect basic differences between whites and blacks with essential hypertension. We emphasize the need to consider race in the investigation of human hypertension.     

Resting and maximal forearm skin blood flows are reduced in hypertension.

To find whether the vasodilator capacity of nonacral skin is reduced in hypertension, we measured forearm blood flow by venous occlusion plethysmography in 10 seated normotensive (mean +/- SD mean arterial pressure, 94 +/- 5 mm Hg) and 10 hypertensive (112 +/- 9 mm Hg) men at rest for 39 minutes while the forearm was heated with water at 42 degrees C, a maneuver known to selectively and maximally vasodilate skin. Blood pressure, measured every 5 minutes, did not change with heating. We found that in the normotensive group resting forearm blood flow was higher (3.64 +/- 1.12 versus 2.48 +/- 0.58 ml/100 ml tissue per minute, p less than 0.001; normotensive group versus hypertensive group) and resting forearm vascular resistance lower (30.17 +/- 10.99 versus 48.88 +/- 17.37 mm Hg.min.100 ml tissue per minute, p less than 0.05; normotensive group versus hypertensive group), and maximal forearm blood flow with local heating was higher (29.32 +/- 11.99 versus 18.19 +/- 4.50 ml/100 tissue per minute, p less than 0.018; normotensive group versus hypertensive group and vascular resistance lower (4.07 +/- 1.04 versus 6.54 +/- 1.17 mm Hg.min.100 ml tissue per minute, p less than 0.005; normotensive group versus hypertensive group). To find whether this degree and duration of local warming maximally vasodilated the skin in hypertensive subjects (as it does in normotensive subjects), we measured forearm skin blood flow before and during local heating plus 10 minutes of ischemia using a laser Doppler flowmeter.(ABSTRACT TRUNCATED AT 250 WORDS)     

Elevated sympathetic nerve activity in borderline hypertensive humans. Evidence from direct intraneural recordings

Reports of elevated plasma catecholamine levels and augmented responses to autonomic blockade suggest increased sympathetic tone in borderline hypertension. It is not known if this reflects greater sympathetic neural outflow. We directly recorded muscle sympathetic nerve activity (microneurography) in 15 normotensive and 12 borderline hypertensive age-matched men to determine whether borderline hypertensive individuals have elevated sympathetic nerve activity. Supine heart rate, blood pressure, plasma norepinephrine, and efferent muscle sympathetic nerve activity (peroneal nerve) were measured after 6 days of both low and high dietary sodium intake (10 and 400 meq sodium/24 hr). Sympathetic nerve activity was elevated significantly in borderline hypertensive individuals on both low (37 +/- 1 in borderline hypertensive individuals vs. 29 +/- 1 bursts/min in normotensive individuals; p less than 0.01) and high (25 + 1 in borderline hypertensive individuals vs. 16 +/- 1 bursts/min in normotensive individuals; p less than 0.01) sodium diets. The borderline hypertensive group had higher systolic (p less than 0.01) and diastolic (p less than 0.05) blood pressures independent of sodium intake. Across both groups, high sodium intake reduced muscle sympathetic nerve activity (p less than 0.001), plasma norepinephrine (p less than 0.001), diastolic blood pressure (p less than 0.02), heart rate (p less than 0.002), and increased weight (p less than 0.005). A significant (p less than 0.05) group-by-diet interaction was observed for plasma norepinephrine levels. Specifically, compared with the normotensive group, plasma norepinephrine levels in the borderline hypertensive group tended to be higher on low sodium diet (p = 0.08) and lower on high sodium diet (p = 0.23).(ABSTRACT TRUNCATED AT 250 WORDS)