bluuebunny/crossref_metadata_2025 huggingface dataset:
Age-dependence of hypertensive-normotensive differences in plasma norepinephrine.
Authors: Goldstein D S , Lake C R , Chernow B , Ziegler M G , Coleman M D , Taylor A A , Mitchell J R , Kopin I J , Keiser H R
Published: June 2012

We compared venous plasma norepinephrine (NE) concentrations in 191 resting, supine patients with essential hypertension and 129 normotensive controls. Among normotensives, plasma NE increased significantly with age, but among hypertensives, no age-related increase occurred, due to relatively high NE values among young hypertensives. When patients and controls less than 40 years old were considered, hypertensives showed significantly higher plasma NE than the controls (317 vs 245 pg/ml, t = 3.15, p less than 0.01); but above the age of 40 years, no significant hypertensive-normotensive difference was obtained. These results, predicted by recent literature reviews, help to resolve the persistent controversy about sympathetic neural activity in essential hypertension, since such activity appears to be abnormal mainly in young patients. The data are consistent with increased sympathetic nervous system activity in the early stages of essential hypertension.
Hypothyroidism as a cause of hypertension.
Authors: Saito I , Ito K , Saruta T
Published: June 2012

To study whether there is an association between hypertension and hypothyroidism, measurements of blood pressure and thyroid function were determined in 477 female patients with chronic thyroiditis. Based on the blood levels of thyroxine (T4) and thyroid stimulating hormone (TSH), 308 patients were considered euthyroid and 169 were hypothyroid [T4 = 2.9 +/- 0.1 micrograms/dl and TSH = 105.8 +/- 6.8 microU/ml (mean +/- SEM)]. Diastolic, but not systolic, blood pressure in hypothyroid patients over 50 years was higher than in euthyroid patients of corresponding age groups. The prevalence of hypertension was higher in hypothyroid patients when hypertension was defined as the systolic and/or diastolic blood pressure above 160/95 mm Hg (14.8% vs 5.5%; p less than 0.01). Correlations between diastolic, but not systolic, blood pressure and either the blood level of triiodothyronine (T3) or T4 was significant (r = - 0.174, p less than 0.01, and r = 0.208, p less than 0.01, respectively) when data from both euthyroid and hypothyroid patients were combined. Adequate thyroid hormone replacement therapy for an average 14.8 months in 14 patients resulted in a normalization of thyroid function and a reduction of blood pressure (p less than 0.01). In four who showed no change in thyroid function due to inadequate replacement therapy, blood pressure remained elevated. These results suggest a close association between hypertension and hypothyroidism.
Similarity of idiopathic aldosteronism and essential hypertension. A statistical comparison.
Authors: McAreavey D , Murray G D , Lever A F , Robertson J I
Published: June 2012

There is clinical, biochemical, and pathological evidence that idiopathic aldosteronism is part of a continuum which includes low-renin and normal-renin essential hypertension. In a retrospective statistical study, 89 patients with essential hypertension have been compared with 22 cases of idiopathic aldosteronism and 34 cases of aldosterone-secreting adrenal adenomas. Measurements of serum sodium, potassium, bicarbonate, and plasma angiotensin II concentrations and estimates of exchangeable sodium and potassium were obtained for individual patients. By using various combinations of these biochemical variables, a statistic, the Mahalanobis distance, was described for each of the three populations, essential hypertension, idiopathic aldosteronism, and adrenal adenomas. For each combination of variables, the distribution of the idiopathic aldosteronism group resembled that of the essential hypertension group more closely than that of the aldosterone-secreting adrenal adenoma group. Thus, the use of this statistical technique provides further evidence of the similarity of essential hypertension and idiopathic aldosteronism.
A model of intervention for prevention of early essential hypertension in the 1980s.
Authors: Berenson G S , Voors A W , Webber L S , Frank G C , Farris R P , Tobian L , Aristimuno G G
Published: June 2012

The onset of essential hypertension early in life is indicated by the high tracking of blood pressure during adolescence; intervention in adults with mild hypertension has been found successful. How, then, can high blood pressure levels in children be modified to prevent early hypertensive cardiovascular disease in adulthood? In an entire biracial town (population 9000) we surveyed 1604 (89%) of all children aged 8--18 years for blood pressure and reexamined those in the upper decile of mean blood pressure (for each race, sex, and height) on three additional occasions. On each examination nine blood pressures were taken by trained observers. All children consistently in the top decile were randomly allocated into either a treatment (n = 50) or comparison (n = 50) group. These two groups and an additional midrange blood pressure comparison group (n = 50) were followed regularly using school facilities including community and school programs. Treatment consisted of 1) dietary guidance; 2) modifications of school lunches and snacks with healthy substitutes; 3) parental involvement; 4) a low dose diuretic and beta-antagonist given by usual standards. All study groups were monitored for blood pressure in a blind manner. In 6 months of observation, blood pressure in the treatment group remained 5 and 3 mm Hg (systolic and diastolic) less than controls (p less than 0.001 and p less than 0.01). An orchestrated community-wide attack on early-stage hypertension is feasible and seems to offer exciting potential for prevention of early hypertensive disease.
Chronic sucrose ingestion induces mild hypertension and tachycardia in rats.
Authors: Buñag R D , Tomita T , Sasaki S
Published: June 2012

As a means for increasing sympathetic activity, male weanling rats were given 8% sucrose solution to drink instead of water. After 5 weeks, systolic pressures measured with a tail-cuff method became appreciably elevated, and the elevation was verified when phasic pressures were later recorded directly from femoral catheters. Successful induction of sympathetic overactivity was considered a likely explanation because sucrose-ingesting rats, compared with untreated controls, had faster heart rates and larger hypotensive responses to alpha-adrenergic blockade with phentolamine. Upon graded electrical stimulation of the ventromedial hypothalamus under urethane anesthesia, resulting pressor and sympathetic nerve responses were also larger in sucrose-treated rats. By contrast, pressor responses to injections of norepinephrine or tyramine were unaffected, thereby indicating that cardiovascular sensitivity had not been enhanced by sucrose ingestion. During intravenous glucose tolerance tests, increases in plasma insulin were consistently lower in sucrose-treated than control rats even though corresponding increases in plasma glucose were just transiently higher. These results support the interpretation that chronic sucrose ingestion inhibits pancreatic insulin secretion and elevates blood pressure by stimulating the ventromedial hypothalamus to increase sympathetic activity.
Asynchronous changes in prorenin and renin secretion after captopril in patients with renal artery stenosis.
Authors: Derkx F H , Tan-Tjiong L , Wenting G J , Boomsma F , Man in 't Veld A J , Schalekamp M A
Published: June 2012

An assay of plasma prorenin was developed in which the conversion to renin occurred under apparently optimal conditions. Some characteristics of the assay were 1) prorenin was activated by Sepharose-bound trypsin at 4 degrees C; 2) the concentration of activator was not critical provided that incubation was prolonged until renin activity had reached a plateau; and 3) this plateau was stable and had the same height as after maximal activation with acid, pepsin, plasmin or urokinase. Maximal activity with Sepharose-bound trypsin at 4 degrees C was higher than with cryoactivation, and optimal conditions were more readily reproduced than with trypsin at 37 degrees C or with acid-activation. The assay was used for measurements in peripheral and renal vein plasma after captopril in hypertensive patients with unilateral renal artery stenosis. Peripheral renin rose within 30 minutes after a first dose of captopril, 50 mg orally, and it remained high with chronic treatment. In contrast, peripheral prorenin fell initially and rose after 4 hours. These changes in peripheral plasma were related to changes in the secretion rates of the two forms of renin from the affected kidney. Thus chronic, but not acute, stimulation of renin release was associated with an increased secretion rate of prorenin. The late rise in prorenin is probably an indication of enhanced synthesis in the kidney, so that more prorenin is available for conversion. The data suggest that prorenin is indeed a biosynthetic precursor of renin and that, at least under certain circumstances, a major proportion of circulating prorenin originates from the kidney.
Continuous vs intermittent blood pressure measurements in estimating 24-hour average blood pressure.
Authors: di Rienzo M , Grassi G , Pedotti A , Mancia G
Published: June 2012

In the past few years noninvasive automatic blood pressure (BP) recorders have been increasingly used to estimate patients' 24-hour BP more accurately than by one or few isolated measurements. However, these recorders only allow BP to be intermittently measured at intervals between 5 to 30 minutes, which means that the number of values collected over 24 hours (10 to 100) remains a tiny fraction of the thousands of values that occur during the same period. To determine whether this represents a limitation to this approach, BP was recorded intraarterially for 24 hours (Oxford method) in 20 ambulant hypertensive patients. A beat-to-beat analysis of the BP recording was provided by a computer, and the average 24-hour systolic, diastolic, and mean BP values were compared with those obtained by analyzing single BP waves of the same recording at intervals of 5, 10, 15, 30, and 60 minutes. In each subject the average 24-hour BP values obtained by the beat-to-beat analysis closely corresponded to those obtained by the analysis performed at 5-, 10-, 15-, or 30-minute intervals. In most subjects, this was the case also when the analysis was performed at 60-minute intervals. These findings demonstrate that intermittency of measurements does not limit the accurate assessment of true average BP. Indeed, accurate assessment can be achieved at intervals as much as 30 or 60 minutes apart.
Progressive hypertension in dogs by avoidance conditioning and saline infusion.
Authors: Anderson D E , Kearns W D , Better W E
Published: June 2012

A group of dogs was trained on a free-operant avoidance-conditioning task that evoked acute increases in arterial pressure and heart rate during each of three daily 30-minute sessions. After 15 days of exposure to this procedure under conditions of normal sodium intake, 24-hour mean levels of arterial pressure remained unchanged. Another group of dogs received continuous intrarterial infusion of isotonic saline at a constant rate of 185 mEq/24 hrs for 15 days, but no avoidance sessions. Again, 24-hour mean levels of arterial pressure did not change significantly. However, 24-hour mean levels of systolic (19.5 +/- 6.2 mm Hg) and diastolic (13.7 +/- 2.9 mm Hg) pressure rose progressively over a 15-day period in a third group of dogs exposed concurrently to the avoidance schedule and saline infusion procedure. The progressive hypertension was accompanied by no consistent changes in heart rate. These experiments indicate that behavioral stress can potentiate sodium hypertension and provide a new method for the study of physiological and behavioral factors in long-term blood pressure control.
Abnormal red blood cell ion transport and hypertension. The People's Gas Company study.
Authors: Trevisan M , Ostrow D , Cooper R , Liu K , Sparks S , Okonek A , Stevens E , Marquardt J , Stamler J
Published: June 2012

A population-based survey of 134 white men, recruited from the Chicago People's Gas Company labor force, was carried out to examine the association between sodium-lithium (Na-Li) countertransport and hypertension. Of the 134 participants in this industry-sponsored periodic health examination, 64 were normotensive and 70 were either taking antihypertensive medications or had a systolic pressure greater than or equal to 140 or a diastolic pressure greater than or equal to 90 mm Hg. The hypertensives were older and more overweight. Countertransport was significantly higher in hypertensives than in normotensives. Among the three subgroups of hypertensives--untreated, borderline (140/90 to 160/95 mm Hg), untreated definite (over 160/95 mm Hg), and treated--an increase in countertransport was consistently observed, significant for the latter two groups. The relationship between countertransport and hypertension was independent of overweight, with countertransport being significantly related to both blood pressure and overweight. Altered ion transport may play an important role in the etiology and/or pathophysiology of hypertension.
Effect of renal denervation on arterial pressure in rats with aortic nerve transection.
Authors: Kline R L , Patel K P , Ciriello J , Mercer P F
Published: June 2012

The role of renal nerves in influencing the control of arterial pressure was studied in Wistar rats with aortic depressor nerve (ADN) transection. Renal denervation prevented or reversed the normal increase in arterial pressure seen after ADN transection. This effect was not due to an effect on the renin-angiotensin system, as the elevated arterial pressure after ADN section in rats with renal nerves intact was shown to be due to increased alpha-adrenergic activity. Food and water intake and urine output decreased significantly in both renal-denervated and sham-denervated rats after ADN section, suggesting that a pressure diuresis mechanism was not responsible for preventing the rise in pressure in renal-denervated rats. In another study, the concentration of norepinephrine in skeletal muscle and hypothalamus at 0 and 8 hours after inhibition of tyrosine hydroxylase with alpha-methyltyrosine was used as an index of norepinephrine turnover. Norepinephrine turnover in skeletal muscle was increased significantly over control values by ADN transection in sham renal-denervated rats, but was not significantly different from controls in renal-denervated rats with ADN section. In the hypothalamus, there was a significant difference between the turnover of norepinephrine in the two groups of ADN-sectioned rats. The results taken together suggest that renal denervation prevents the arterial pressure response to ADN transection by altering the central mechanisms governing sympathetic outflow. It is suggested that this effect may be due to elimination of information carried by afferent renal fibers.
Changes in paraventricular vasopressin and oxytocin during the development of spontaneous hypertension.
Authors: Morris M , Keller M , Sundberg D K
Published: June 2012

The potential role of central neuroendocrine changes in the development of spontaneous hypertension was evaluated. The developmental changes in blood pressure and hypothalamic and plasma levels of vasopressin (AVP) and oxytocin (OT) were determined in groups of SHR and WKY animals from 3 to 24 weeks of age. Hypothalamic OT content was significantly lower in 3-, 6-, and 12-week-old SHR rats compared to age-matched WKY animals. Hypothalamic AVP content was not different at 3 weeks of age, but was lower in the SHRs at 6 and 12 weeks. To localize strain differences in AVP and OT, specific hypothalamic nuclei were removed from 300 microns frozen brain sections, and hormone content measured. Paraventricular AVP and OT content was lower in the SHRs which had increased blood pressure (6, 12, and 24 weeks of age) but not in the prehypertensive groups (3 weeks of age). Neuropeptide content was unchanged in the supraoptic nucleus or median eminence. Plasma levels of AVP were increased in the SHR, while OT was unchanged. Thus, genetic hypertension is associated with specific and localized changes in hypothalamic AVP and OT. The fact that the peptide deficit occurred in the paraventricular nucleus, a region thought to be involved in the control of autonomic function, may have important implications in terms of the pathogenesis of hypertension.
Mechanisms in human renovascular hypertension.
Authors: Maslowski A H , Nicholls M G , Espiner E A , Ikram H , Bones P J
Published: June 2012

To clarify the pathophysiology of renovascular hypertension, we monitored intraarterial pressure continuously and measured hourly hormone levels for 24 hours under carefully controlled conditions in two hypertensive patients with unilateral renal artery occlusion. Comparison of the results with those obtained when the patients were normotensive 3 months after uninephrectomy indicated that, while the renin-angiotensin system played a central role in maintaining the hypertension, the sympathetic nervous system also contributed and, in addition, modulated short-term arterial pressure fluctuations. In the untreated state, the sympathetic regulation of renin secretion was heightened, and angiotensin II/aldosterone dose-responsiveness was augmented. It is suggested that these adaptive changes might serve to offset the tendency to severe sodium depletion and thence exacerbation of the hypertension.
Captopril stimulation of differential renins in renovascular hypertension.
Authors: Lyons D F , Streck W F , Kem D C , Brown R D , Galloway D C , Williams G R , Chrysant S G , Danisa K , Carollo M
Published: June 2012

Twenty-six patients being evaluated for renovascular hypertension were studied to assess the diagnostic value of enhancing the differential between renal venous renins (PRA) by a single 25 mg oral dose of converting enzyme inhibitor (CEI, captopril). Antihypertensive medications were not discontinued prior to the study, and renal venous effluent was sampled before and 30 minutes after CEI. Eight patients without stenosis who did not have surgery had post-CEI ratios of less than 3.0. The other 18 patients had operative intervention, with 14 subsequently having improved blood pressure control. Of these 14, seven patients with unilateral stenosis, four patients with bilateral stenosis, and one patient without overt stenosis but with other evidence of reduced renal blood flow had 30-minute PRA ratios of 3.0 or greater. Five of these 14 patients had prestimulation ratios of less than 1.5 and might not be considered operative candidates by conventional criteria. Four other patients unimproved by surgery had post-CEI ratios of less than 3.0 despite a baseline ratio of greater than 1.5 in two of four. Only two patients with post-CEI ratios of less than 3.0 were improved with surgery. We conclude that a 30-minute post-CEI renal venous ratio of 3.0 or greater enhances the probability that patients with renovascular disease, and hypertension will respond to surgical intervention with improved blood pressure control.
Evidence that blood pressure reduction by serotonin antagonists is related to alpha receptor blockade in spontaneously hypertensive rats.
Authors: Cohen M L , Fuller R W , Kurz K D
Published: June 2012

In vitro affinity for vascular 5HT2 and alpha receptors was determined for several compounds (spiperone, ketanserin, mianserin, trazodone, mepiprazole, benzoctamine, m-trifluoro-methylphenylpiperazine, m-chlorophenylpiperazine, and 1-(1-naphthyl)piperazine) known to interact with serotonin receptors. All compounds competitively inhibited 5HT2 and alpha receptors with differing degrees of selectively. Based on these observations, ketanserin, benzoctamine, and 1(1-naphthyl)piperazine were evaluated as antihypertensive agents in spontaneously hypertensive rats (SHR). Of these compounds, 1-(1-naphthyl)piperazine was a highly selective 5HT2 receptor antagonist with a ratio of 5HT2 to alpha receptor affinity of greater than 2000. The ratio of 5HT2 to alpha receptor affinity for ketanserin and benzoctamine was 63 and 16, respectively. However, the order of affinity toward 5HT2 receptors was ketanserin greater than 1-(1-naphthyl)piperazine greater than benzoctamine whereas the order of affinity toward alpha receptors was ketanserin greater than benzoctamine greater than 1-(1-naphthyl)piperazine. A similar order of potency toward both 5HT2 and alpha receptors was found in pithed SHR based on antagonism of the pressor response to serotonin and methoxamine, respectively. In the SHR, maximum blood pressure reduction at a dose of 10 mg/kg i.p. was approximately 65 and 30 mm Hg for ketanserin and benzoctamine, respectively; 1-(1-naphthyl)piperazine did not affect blood pressure. Thus, blood pressure reduction more closely paralleled the in vitro and in vivo potency of these agents toward vascular alpha rather than 5HT2 receptors.(ABSTRACT TRUNCATED AT 250 WORDS)
In vivo production of prostaglandin I2 in Dahl salt-sensitive and salt-resistant rats.
Authors: Falardeau P , Martineau A
Published: June 2012

Prostaglandin I2 (PGI2, prostacyclin), a potent vasodilator synthesized by the blood vessels, has been postulated to play a role in hypertension. The purpose of our study was to test this hypothesis by monitoring the in vivo production of PGI2 in Dahl salt-sensitive (S) and salt-resistant (R) rats under normal and high sodium intake. The 24-hour urinary excretion of two endogenous metabolites of PGI2, 2-,3-dinor-6-oxo-PGF1 alpha, an 2,3-dinor-13,14-dihydro-6,15-dioxo-PGF1 alpha was measured by combined gas chromatography-mass spectrometry (GC-MS) and used as an index of the total production of PGI2 by the animals. The pattern of urinary excretion of these two metabolites in the R and the S rats during the control period indicated that, under normal conditions, early in life the basal production of PGI2 was the same in both groups of rats. Following the chronic administration of a high sodium diet (8.1% sodium chloride, starting at 36 days of age), a significant and sustained increase in the urinary excretion of 2,3-dinor-6-oxo-PGF1 alpha was documented in the R rats (from 37 +/- 7 ng/24 hrs at age 35 days to 63 +/- 7, 52 +/- 4, and 56 +/- 10 ng/24 hrs at 50, 60, and 80 days, respectively), whereas the urinary levels of this metabolite decreased slightly in the S rats (from 41 +/- 7 ng/24 hrs at age 35 days to 25 +/- 5, 30 +/- 6, and 28 +/- 9 ng/24 hrs at 50, 60, and 80 days, respectively). During the same period, the R rats remained normotensive (103 +/- 5 mm Hg, systolic pressure) while the arterial pressure of the S rats increased gradually (to 142 +/- 8 and 180 +/- 19 mm Hg at ages 60 and 80 days, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)
Hemodynamic mechanisms of adaptation to chronic high sodium intake in normal humans.
Authors: Sullivan J M , Ratts T E
Published: June 2012

The long-term hemodynamic effects of a high dietary sodium intake were studied in 10 young normal subjects. After a 4-day diet of 10mEq of sodium and 60 mEq of potassium per day the mean arterial blood pressure (MAP) was 82.3 +/- 15.1 mmHg, the cardiac index (CI) was 2.32 +/- 0.69 liter/min/m2, and total peripheral resistance (TPR) was 1778 +/- 947 dyne sec cm-5. After 4 to 6 days of 200 mEq of sodium and 60 mEq of potassium per day, MAP was 84.3 +/- 20.9 mm Hg, CI had risen to 2.53 +/- 0.61 liter/min/m2, and TPR fell to 1437 +/- 328 dyne sec cm-5. After 6 months of unrestricted sodium intake, urinary sodium excretion (UNa) was 144.1 +/- 51.9 mEq/24 hrs (p less than 0.001), MAP remained at 83.1 +/- 13.8 mm Hg, CI had risen to 3.11 +/- 1.01 liter/min/m2 (p less than 0.05) and TPR was 1268 +/- 444 dyne sec cm-5. After 12 months, UNa had risen to 171.5 +/- 97.6 mEq/24 hrs (p less than 0.005), while MAP remained at 82.4 +/- 17.9 mm Hg, CI at 3.08 +/- 1.16 liter/min/m2 (p less than 0.05), and TPR at 1282 +/- 500 dyne/sec/cm-5. Thus, cardiac index rises significantly with sodium intake in normal subjects and remains at a higher level for as long as 12 months. Blood pressure does not rise because TRP falls proportionately.
Clinical effectiveness and cost-effectiveness of monitoring blood pressure of hypertensive employees at work.
Authors: Logan A G , Milne B J , Flanagan P T , Haynes R B
Published: June 2012

In this randomized controlled trial, the value of using occupational health nurses (OHNs) to monitor the care of hypertensive employees at work was compared with regular care (RC) delivered in the community. One year after entry, the blood pressure level, medication history, compliance with treatment, and cost of hypertensive care of the participants were determined by independent evaluators. The reduction in diastolic blood pressure (DBP), the measure of effectiveness, was 10.5 +/- 1.1 mm Hg (mean +/- SEM) in the OHN group and 7.7 +/- 1.1 mm Hg in the RC group, and the proportion under good blood pressure control was 41.8% and 31.0% respectively. These between-group differences were not statistically significant. Although the employees in the OHN group were more medicated and had a lower treatment dropout rate, neither difference was statistically significant. In addition, the proportion of employees who were compliant with prescribed medication was virtually identical in both groups. The cost of the care received by employees in the OHN group of $ 404.14 for the year was substantially higher than that of $ 250.15 in the RC group with the difference principally related to the cost of visiting the OHNs and a significant difference in drug cost (p less than 0.006). The incremental cost-effectiveness (C/E) ratio of $ 53.67 per mm Hg DBP reduction per year for onsite blood pressure monitoring was higher than the base C/E ratio of $ 32.65 per mm Hg for regular care. Our findings indicate that monitoring the blood pressure of hypertensive employees at work is neither clinically effective nor cost-effective.(ABSTRACT TRUNCATED AT 250 WORDS)
Echocardiographic left ventricular hypertrophy as related to arterial pressure and plasma norepinephrine concentration in arterial hypertension. Reversal by atenolol treatment.
Authors: Corea L , Bentivoglio M , Verdecchia P
Published: June 2012

We tried to assess relationships between echocardiographic left ventricular hypertrophy (LVH), arterial pressure levels, and plasma norepinephrine concentration (NE) in 20 previously untreated stable hypertensive patients with LVH, and in 11 healthy normotensive control subjects. Interventricular septal (IVS) thickness, posterior wall (PW) thickness, and left ventricular mass index (LVMI) were related to arterial pressure levels and to NE by univariate and multivariate regression analyses. In addition, after 18 months of monotherapy with atenolol (carried out in nine of 20 patients), the relationship between echocardiographic changes and degree of pressure reduction was tested. Before treatment, PW thickness weakly correlated with systolic (r = 0.55; p less than 0.01) and mean (r = 0.50; p less than 0.05) arterial pressure. IVS thickness weakly correlated with NE (r = 0.53; p less than 0.05). On this relatively small sample, multivariate regression analysis showed an association of both IVS thickness (R = 0.57; p less than 0.05) and PW thickness (R = 0.58; p less than 0.05) with mean arterial pressure (MAP) and NE. After atenolol, there was a reduction in IVS thickness (1.15 to 1.02 cm; p less than 0.01), PW thickness (1.08 to 0.99 cm; p less than 0.01), and LVMI (136.3 to 113.8 g/m2; p less than 0.01), besides a significant reduction in blood pressure and heart rate. The degree of pressure reduction induced by treatment did not correlate the change in IVS or PW thickness. In contrast, the change in diastolic and mean arterial pressure positively correlated the change in LVMI (r = 0.72 and r = 0.75, respectively; both p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)
Adenosine and metabolic regulation of coronary blood flow in dogs with renal hypertension.
Authors: Ely S W , Sun C W , Knabb R M , Gidday J M , Rubio R , Berne R M
Published: June 2012

It has been demonstrated that resting coronary vascular resistance is elevated with chronic hypertension and concomitant cardiac hypertrophy. The present study employed a model of 6-week, one-kidney, one wrapped Page hypertension to determine if the ability of the heart to match an increase in oxygen demand with an increase in oxygen supply (coronary blood flow) is impaired, and to determine if these vasoregulatory abnormalities are attributable to inadequate adenosine release. Studies were performed in a pentobarbital anesthetized, open-chest canine preparation using a pericardial infusate method to determine adenosine release. Results showed that dobutamine (a beta-receptor agonist) induced increases in myocardial oxygen consumption (MVO2) over a physiological range (8-30 ml O2 X min-1 X 100 g-1) that were accompanied by an increase in coronary blood flow (CBF) with no change in oxygen extraction. The relationship between MVO2 and CBF was not different between the normotensive (NTC) and hypertensive (RHT) animals. Pericardial infusate adenosine (PI ADO) concentrations were not different for the same MVO2 and CBF, and the relationships for MVO2 vs PI ADO as well as PI ADO vs CBF were unaltered by hypertension. However, the relationship between PI ADO and coronary vascular resistance (CVR) was altered in the RHT group such that a given PI ADO concentration was associated with a significantly higher CVR. These data suggest that, over the range of MVO2 studied, there are no limitations in metabolic regulation of the coronary circulation of RHT animals, and that the higher CVR encountered in the RHT group is not the result of a reduced release of the endogenous vasodilator, adenosine.
Impaired catecholamine inactivation. A prohypertensive stimulus after dietary linoleate deficiency in salt-loaded rats?
Authors: Hoffmann P , Taube C , Beitz J , Förster W , Poleshuk W S , Markov C M
Published: June 2012

Experiments were carried out on salt-loaded rats (1.5% NaCl as drinking fluid) to further explore the mechanisms by which blood pressure increases after a linoleic acid-deficient (LAd) diet. In 4-week-old LAd rats (0.5 cal% LA, hydrogenated palm kernel fat) compared to linoleic acid-rich rats (LAr, 13.3 cal% LA, sunflower oil), we observed, from the base of a reduced content of omega-6-polyunsaturated fatty acids in the tissues, an increase in blood pressure by 12 mm Hg (p less than 0.001), a diminished formation of prostaglandin E (PGE), and an unchanged formation of PGF in the aorta as well as a reduction in the in vitro uptake of 14C-norepinephrine into cardiac, aortic, and renal tissues, and a reduced degradation rate of 14C-norepinephrine in cardiac tissue. These differences in LAr vs LAd rats were not exaggerated. With respect to aortic PGE formation, 14C-norepinephrine uptake into aortic and renal tissues and 14C-norepinephrine degradation even lessened when the diet was begun prenatally, although the reduction of omega 6-polyunsaturated fatty acids in the tissues was aggravated. Our conclusion is that a fault in catecholamine inactivation may be involved in the pathogenesis of increased sympathetic activity and blood pressure elevation in LAd-fed, salt-loaded rats, possibly via alterations of endogenous prostanoid formation.
5-HT, alpha-adrenoceptors, and blood pressure. Effects of ketanserin in essential hypertension and autonomic insufficiency.
Authors: Wenting G J , Woittiez A J , Man in't Veld A J , Schalekamp M A
Published: June 2012

The serotonin (5-hydroxytryptamine, 5-HT) antagonist, ketanserin, has a high affinity for 5-HT2-receptors but it also binds to alpha 1-adrenoceptors. The compound (10 mg i.v.) lowered mean arterial pressure by 22% +/- 2% (mean +/- SEM, p less than 0.001) in 30 patients with essential hypertension. Measurements of heart rate, cardiac output, cardiac filling pressures, forearm blood flow, renal blood flow, and glomerular filtration rate revealed a hemodynamic pattern compatible with vasodilation of both resistance and capacitance vessels. This was accompanied by moderate reflex cardiostimulation. Ketanserin did not alter the pressor effect of bolus injections of (-)-phenylephrine hydrochloride (25, 50, 100, and 200 micrograms i.v.). Ketanserin also had a distinct hypotensive effect in four normotensive patients with autonomic insufficiency due to an efferent sympathetic lesion, who were unresponsive to phentolamine (20 mg i.v.). Thus, ketanserin in the dose we have used appears to lower blood pressure independently of alpha 1-adrenoceptor blockade. On the other hand, in patients with essential hypertension the antihypertensive effect of ketanserin was blunted by pretreatment with prazosin (12 mg/day). Therefore, a certain degree of alpha 1-adrenergic tone seems to be required for the compound to exert its full antihypertensive action. The findings are indirect evidence for a role of 5-HT in the maintenance of increased vascular resistance in essential hypertension. This may be related, at least in part, to the alleged amplifying effect of 5-HT on alpha 1-adrenoceptor-mediated vasoconstriction.
Ambulatory blood pressure recordings. Reproducibility and unpredictability.
Authors: des Combes B J , Porchet M , Waeber B , Brunner H R
Published: June 2012

The accuracy of blood pressure readings taken by the portable semiautomatic blood pressure recorder Remler M 2000 was investigated in 101 unselected, untreated volunteers. On the average, pressures recorded during usual daily activities were lower by approximately 10 mm Hg than pressures measured in the office. However, individual ambulatory pressures could not be predicted from office readings, and the difference varied among the volunteers from +14 to -43 mm Hg. The reproducibility of office and ambulatory pressures was investigated in 84 subjects. There was a highly significant correlation between pressure levels determined at a 3- to 4-month interval with both the conventional auscultatory method in the office and the Remler ambulatory recorder. These data demonstrate that the Remler M 2000 ambulatory blood pressure recorder, when used properly, provides reproducible blood pressure profiles during customary daily activities. The ambulatory pressure recorder seems particularly useful for a baseline evaluation of the usual daily blood pressure, which in the individual subject differs in a highly unpredictable manner from the blood pressure measured at the physician's office.
Salt sensitivity in humans is linked to enhanced sympathetic responsiveness and to enhanced proximal tubular reabsorption.
Authors: Skrabal F , Herholz H , Neumayr M , Hamberger L , Ledochowski M , Sporer H , Hörtnagl H , Schwarz S , Schönitzer D
Published: June 2012

If high sodium intake is involved in the pathogenesis of essential hypertension, the effects of changing the sodium intake should be demonstrable in the susceptible part of the normotensive population. Therefore, we have investigated the effects of moderate salt restriction in 52 young normotensive subjects with and without a family history of hypertension; 22 (42%) responded to moderate salt restriction (200 to 50 mmol/day) over 2 weeks, with a significant fall in blood pressure shown by continuous automatic blood pressure recordings. Accordingly, these subjects were classified as salt-sensitive, and the remainder as salt-resistant. Compared to salt-resistant subjects, salt-sensitive subjects showed a 2.5-fold higher incidence of a positive family history of hypertension (p less than 0.01), and a significantly higher blood pressure and lower salivary sodium concentration during the usual high sodium diet. Although there were no differences in Na,K-ATPase activity and in Na-K cotransport of erythrocytes, the pressor response to infused norepinephrine in salt-sensitive subjects was double that of salt-resistant subjects independent of the diet and this was linked to indirect evidence for enhanced proximal tubular sodium reabsorption. On the usual high sodium diet, 40% of the normal population may be salt-sensitive and prone to develop hypertension. Hypersensitivity to catecholamines (genetically determined?) may be the cause of salt sensitivity. A low sodium concentration in saliva deserves further study as a simple screening test to identify salt-sensitive subjects.
Hemodynamic and antihypertensive effects of the new oral angiotensin-converting-enzyme inhibitor MK-421 (enalapril).
Authors: Fouad F M , Tarazi R C , Bravo E L , Textor S C
Published: June 2012

The antihypertensive, hemodynamic, and humoral effects of the new converting-enzyme inhibitor enalapril (MK-421) were assessed by sequential studies during 3 months of uninterrupted treatment (20 mg twice daily) in 10 hypertensive patients. Six achieved good blood pressure (mean arterial pressure) control with enalapril alone (from 126 +/- 7.0 mm Hg pretreatment to 105 +/- 1.6 mm Hg at 3 months, p less than 0.05). The other four required the addition of diuretics (hydrochlorothiazide 25 mg orally twice daily) at different stages of follow-up, with resultant blood pressure control (128 +/- 9.6 mm Hg pretreatment to 113 +/- 1.9 mm Hg at 2 months after the addition of diuretics). Neither the acute nor long-term blood pressure response could be predicted from the pretreatment levels of plasma renin activity. The blood pressure reduction during enalapril therapy was characterized by a decrease in total peripheral resistance (53 +/- 2.5 U X M2 pretreatment to 38 +/- 3.0 U X M2 at 3 months, p less than 0.05) with no significant change in cardiac output or heart rate. This lack of reflex tachycardia could not be ascribed to baroceptor dysfunction since the response to head-up tilt (the increase in diastolic blood pressure, in heart rate, and in plasma catecholamines) was normal and not significantly different from pretreatment response. Average blood volume did not change (91% +/- 4.3% of normal in the pretreatment period to 93% +/- 2.9% after 3 months of therapy, p = NS) despite the significant lowering of arterial pressure with enalapril alone (n = 6).(ABSTRACT TRUNCATED AT 250 WORDS)
Factors related to tracking of blood pressure in children. U.S. National Center for Health Statistics Health Examination Surveys Cycles II and III.
Authors: Lauer R M , Anderson A R , Beaglehole R , Burns T L
Published: June 2012

In this paper we examine the relationship of growth, obesity, and the degree of sexual and bone maturation to blood pressure in a U.S. national probability sample of 2165 children examined by the U.S. National Center for Health Statistics on two occasions, approximately 4 years apart. Subjects who maintained, increased, or decreased their peer rank order of blood pressure are described. Children who maintained their blood pressure in the upper quintile were taller, heavier, more obese, had greater bone age, greater numbers of permanent teeth, and were more sexually mature than their peers, while those maintaining their blood pressure in the lowest quintile of blood pressure were shorter, lighter, less obese, had lesser bone age, fewer permanent teeth, and were less sexually mature. Subjects whose blood pressures were initially in the lowest four quintiles and then rose to the top quintile were also taller, heavier, more obese, and had greater bone age, while those with blood pressures falling to the lowest quintile from the upper four quintiles were shorter, lighter, less obese, and had lesser bone age. Thus, the level at which blood pressure tracks during childhood is related to growth, obesity, and to the degree of maturation acquired. In addition, children whose blood pressures are rising or falling in relation to their peers have body growth and maturation characteristics similar to those who maintain their rank order high or low respectively.
Milk consumption, calcium intake, and decreased hypertension in Puerto Rico. Puerto Rico Heart Health Program study.
Authors: Garcia-Palmieri M R , Costas R , Cruz-Vidal M , Sorlie P D , Tillotson J , Havlik R J
Published: June 2012

The baseline observations in the Puerto Rico Heart Health Program during 1965-1968 involved blood pressure determinations, other measurements, and a 24-hour dietary recall in 7932 men aged 45-64 years. This extensive data base provided an opportunity to test the hypothesis that low calcium intake is related to increased blood pressure level. Among men without baseline coronary heart disease and not taking antihypertensive medication, there was an inverse relationship between milk consumption and definite hypertension in urban Puerto Rican men and older rural men. When data from all age and area groups had been averaged, a twofold increase in hypertension was found in subgroups who drank no milk compared to those who consumed over 1 quart of milk a day. Similar trends were found when an estimate of total calcium intake from food, principally from milk, was used. With multivariate analysis while known correlates of blood pressure were simultaneously considered, an independent effect persisted between milk consumption and blood pressure. These results appeared to confirm an inverse association between calcium and hypertension. It was still not possible to ascribe a causal relationship between calcium and blood pressure, however, due to the intricate network of covarying food intakes, the factors related to absorption or lack of absorption of calcium, and the possible role that unmeasured social and cultural factors may play in the observed relations.
Blood pressure and associated factors in a rural Kenyan community.
Authors: Poulter N , Khaw K T , Hopwood B E , Mugambi M , Peart W S , Rose G , Sever P S
Published: June 2012

Blood pressure (BP) and associated factors were determined in 1737 men in a remote Kenyan agricultural community. Systolic BP showed no significant rise with age until after 54 years; diastolic BP showed a small rise with age. Both systolic and diastolic BP correlated with weight independent of age. Systolic and diastolic BP correlated positively with casual urinary sodium/potassium and negatively with potassium/creatinine ratios. Both systolic and diastolic BP correlated significantly with the number of years of education, as did urinary sodium/potassium and sodium/creatinine ratios. Potassium/creatinine ratios were negatively correlated with the number of years of education. Blood pressure and urinary sodium/creatinine ratios were significantly lower in subsistence farmers compared with those in other occupations, and potassium/creatinine ratios were significantly higher. Two pilot studies of Luo tribesmen showed a strong correlation between casual urinary electrolyte ratios and those derived from 24-hour urine samples and a greater variance of sodium excretion between these people than that found within individuals. These results suggest that a relationship between BP and casual urine electrolyte estimations may be identifiable in communities where there is less day-to-day dietary variation. They also suggest that some of the changes in BP associated with urbanization could be mediated by changes in dietary electrolytes.
Blood pressure experience and risk of cardiovascular disease in the elderly.
Authors: Harris T , Cook E F , Kannel W , Schatzkin A , Goldman L
Published: June 2012

For the 1254 persons in the Framingham Heart Study who survived to age 65 without prior cardiovascular disease or prior use of antihypertensive medications, significant univariate correlates of the development of cardiovascular disease after age 65 included (1) the systolic blood pressure at age 65, (2) the average systolic blood pressure before age 65, and (3) the slope of blood pressure change up to age 65. After controlling for the systolic blood pressure at age 65, average pre-age 65 blood pressure remained significant (p less than 0.05) and the slope of the pre-age 65 blood pressure was marginally significant (p = 0.06). Even after controlling for the mean of up to three blood pressure measurements at age 65, an average systolic blood pressure of 160 mm Hg or greater before age 65 was an independently significant predictor of the post-age 65 development of cardiovascular disease (rate ratio = 1.79; 95% confidence interval = 1.04, 3.07). These data suggest that even after performing multiple measurements at a single examination, knowledge of past systolic blood pressure history, especially if it averages 160 mm Hg or greater, adds a small but statistically significant increment in predicting future cardiovascular disease in the elderly.
Oral load of tyrosine or L-dopa and plasma levels of free and sulfoconjugated catecholamines in healthy men.
Authors: Cuche J L , Prinseau J , Selz F , Ruget G , Tual J L , Reingeissen L , Devoisin M , Baglin A , Guédon J , Fritel D
Published: June 2012

The levels of free and sulfoconjugated catecholamines were measured in the plasma of fasting, recumbent normal subjects before and after an oral load of the catecholamine precursors tyrosine or L-dopa. Basal values of sulfoconjugated catecholamines, measured in plasma samples diluted 1:100 were 7998 +/- 540 pg/ml for dopamine sulfate, 2938 +/- 281 pg/ml for norepinephrine sulfate, and 2958 +/- 288 pg/ml for epinephrine sulfate (n = 37 tests in 15 men); these basal values are higher than those reported previously. Neither free nor sulfoconjugated catecholamine concentrations were changed by a tyrosine load (100 mg/kg) that induced a doubling of the plasma tyrosine level or by a meal low in phenylalanine and tyrosine (but otherwise supplying constituents of normal nourishment) that induced a greater than 50% reduction in the plasma tyrosine concentration. After an oral load of L-dopa (125 mg) the following were observed. (1) An extremely large increase (greater than 100-fold) in dopamine sulfate levels was noted, an increase that was less marked in the same subjects given L-dopa (125 mg) plus the peripheral dopa-decarboxylase inhibitor carbidopa (12.5 mg); as expected, free dopamine concentration also was increased. (2) Neither free nor sulfoconjugated norepinephrine concentrations were altered. (3) Epinephrine sulfate but not free epinephrine concentration was increased (more than ten-fold) after L-dopa ingestion alone; this result was unexpected and has to be confirmed before considering its physiological meaning, if any.
The sympathetic nervous system and hypertension in primary aldosteronism.
Authors: Bravo E L , Tarazi R C , Dustan H P , Fouad F M
Published: June 2012

To assess the role of the sympathetic nervous system in mineralocorticoid hypertension in humans, results from 24 patients with aldosterone-producing adenoma were compared with those in 27 appropriately matched essential hypertensive subjects and 26 normotensive subjects. Resting plasma catecholamine levels averaged 292 +/- 140 (SD) pg/ml in patients with aldosterone-producing adenoma, 305 +/- 101 in patients with essential hypertension, and 260 +/- 120 in normotensive subjects; none of the differences among the three groups was significant. With head-up tilt (60 degrees for 10 min) plasma catecholamine levels increased similarly in the aldosterone-producing adenoma and essential hypertensive groups (up to 681 +/- 111 and 611 +/- 57 pg/ml respectively, NS). beta-Blockade (propranolol, 10 mg i.v.) in eight aldosterone-producing adenoma patients decreased heart rate (from 78 +/- 5 to 68 +/- 3 beats/min, p less than 0.005) and cardiac output (from 5.5 +/- 0.4 to 4.6 +/- 0.3 liter/min, p less than 0.001), but left mean blood pressure unchanged (127 +/- 4 to 127 +/- 2 mm Hg). Combined alpha- and beta-blockade with phentolamine and propranolol in five patients with aldosterone-producing adenoma produced no detectable changes in blood pressure. Thus, results from biochemical, functional, and pharmacological studies in humans showed no evidence of enhanced peripheral sympathetic activity in the hypertension of primary aldosteronism.