bluuebunny/crossref_metadata_2025 huggingface dataset:
The cardiovascular responses to exercise in children across the blood pressure distribution. The Muscatine study.
Authors: Schieken R M , Clarke W R , Lauer R M
Published: June 2012

Children with elevated systolic blood pressure have a wide range of cardiac output. To better understand the mechanisms regulating resting and exercise blood pressure, we investigated the cardiovascular responses to both dynamic and isometric exercise in 264 children who were selected from the low, middle, and upper quintile of the distribution of blood pressure of an entire school population. We sought to identify patterns of response to exercise that correlated with both resting cardiac output and resting blood pressure. During isometric exercise, systolic pressure adjusted for age and body size increased in all groups. The low group's mean pressure remained significantly lower than the high group's pressure throughout the entire exercise period. Body size adjusted group systolic and diastolic blood pressure level differences exist during dynamic exercise. The product of the systolic blood pressure times the heart rate, in the high blood pressure group, was significantly higher throughout dynamic exercise than in the other two groups. Elevated resting resistance is correlated with elevated resistance during isometric exercise and elevated diastolic blood pressure during dynamic exercise. Cardiac index had a significant negative correlation to age (r = -0.58) at all levels of blood pressure. This observation, in children, lends some support to the concept of the evolution from a hyperkinetic circulation in early childhood to a circulation with lower cardiac output and more elevated systemic vascular resistance at an older age.
The role of renin substrate in hypertension.
Authors: Gordon D B
Published: June 2012

A positive correlation between blood pressure and renin substrate concentration is found in a wide variety of conditions in human beings and in animal experiments. The evidence concerning this relationship is reviewed and the exceptions are discussed. The frequent positive correlation between renin substrate and elevated blood pressure suggests that increased renin substrate concentration may be a causal factor in hypertension.
Role of the renal nerves in the maintenance of DOCA-salt hypertension in the rat. Influence on the renal vasculature and sodium excretion.
Authors: Katholi R E , Naftilan A J , Bishop S P , Oparil S
Published: June 2012

We previously observed that the renal nerves facilitate sodium retention and contribute to the development of DOCA-salt hypertension in the rat. To determine whether the renal nerves also participate in the maintenance of DOCA-salt hypertension, we studied the effects of renal denervation after 3 or 10 weeks of DOCA-salt treatment on systolic blood pressure, urinary sodium excretion, creatinine clearance, and precapillary arteriolar wall/lumen ratios of renal, hindlimb muscle, and cremaster muscle vascular beds. Systolic blood pressures of animals given DOCA-salt reached a plateau by 3 weeks of treatment at which time a sham operation or renal denervation was performed. Sham operation in hypertensive animals resulted in no change in systolic blood pressure and no change in percent sodium intake excreted. Wall/lumen ratio of the renal precapillary arteriole in sham-operated hypertensive animals was increased compared to similar sized vessels in hindlimb and cremaster muscle. In contrast, renal denervation resulted in a natriuresis and an attenuation of the hypertension (208 +/- 7 mmHg; p less than 0.01). Wall/lumen ratio of the renal capillary arterioles in renal denervated animals was no different than similar sized vessels in hindlimb and cremaster muscle and significantly less than that seen in sham-operated animals (0.85 +/- 0.05 vs 1.03 +/- 0.06; p less than 0.05). In another group of animals, sham operation or renal denervation was performed after 10 weeks of DOCA-salt treatment. At this time neither operation altered systolic blood pressure or sodium balance. In contrast to 3-week DOCA-salt-treated hypertensive sham-operated animals, renal precapillary arteriolar wall/lumen ratio of 10-week animals was no different than similar sized vessels in hindlimb and cremaster muscle. In addition, renal precapillary arteriolar wall/lumen ratio of 10-week DOCA-salt-treated renal-denervated animals was no different than that seen in 10-week DOCA-salt-treated sham-operated hypertensive animals. Creatinine clearance of the 10-week DOCA-salt-treated sham-operated or renal-denervated animals was significantly (p less than 0.01) lower than that of the 3-week DOCA-salt-treated groups (0.25 +/- 0.14 vs 1.03 +/- 0.10 ml/min). These data suggest that the renal nerves contribute to the early established phase of DOCA-salt hypertension by shifting the arterial pressure-renal sodium excretion curve to the right. With time, the renal nerves play a diminishing role in the maintenance of established DOCA-salt hypertension in the rat, while other renal factors, including decreased glomerular filtration rate and probable fixed renal vascular changes, play an increasingly important role.
Relationship between plasma norepinephrine and sympathetic neural activity.
Authors: Goldstein D S , McCarty R , Polinsky R J , Kopin I J
Published: June 2012

For circulating norepinephrine (NE) to reflect sympathetic activity validly, plasma NE should show an intensity-dependent increase during sympathetic stimulation and decrease during sympathetic inhibition, and circulating NE should correlate with more directly obtained measures of sympathetic activity. Review of published evidence indicates that NE in peripheral plasma satisfies these criteria. However, models used to explain the relationship between circulating NE and sympathetic activity must take into account processes intervening between the synaptic cleft and free NE in the circulation and, since sympathetic outflow is regionalized, the contributions of specific vascular beds to circulating NE. In this report a model is presented where removal processes for NE are viewed as acting in series to produce a gradient in NE concentrations from synapse to plasma, and where the relative contributions of specific vascular beds are calculated from the arteriovenous difference in plasma NE across those beds and the percentage of cardiac output distributed to them. In general, venous plasma NE provides a useful estimation of average sympathetic outflow.
Training and certification of blood pressure observers.
Authors: Curb J D , Labarthe D R , Cooper S P , Cutter G R , Hawkins C M
Published: June 2012

Accurate, reproducible measurements of blood pressure (BP) were central to the goals and objectives of the Hypertension Detection and Follow-Up Program (HDFP), a multicenter clinical trial on the efficacy of pharmacological treatment of individuals with elevated BP. All potential BP observers with or without previous experience in measuring BP were required to undergo a defined training program and meet set performance criteria to be certified to take HDFP BP. Recertification was required twice a year. Originally an audiotape test was used to measure accuracy of BP readings. This approach was later replaced by a videotape test, which proved more realistic and an equally effective tool for long-term quality control. With this technique of certifications, 75% of the individuals taking the test passed on the first attempt and more than 95% passed with one or two attempts. Although agreement for blinded BP duplicates was generally good, the appearance of sound (systolic BP) was identified with greater reproducibility than was the disappearance (diastolic BP). These recertification procedures were of great value in assuring the continued high quality of our BP data.
Attenuation of the development of spontaneous hypertension in rats by chronic central administration of captopril.
Authors: Okuno T , Nagahama S , Lindheimer M D , Oparil S
Published: June 2012

Captopril infused into the lateral ventricle (ICV) of adult spontaneously hypertensive rats (SHR) decreases blood pressure. The current study was designed to explore the effects of brain converting-enzyme inhibition in young animals before the development of established hypertension and to characterize changes induced by captopril in a variety of pressor systems that might be responsible for the development of hypertension in this strain. Captopril (1.25 micrograms/0.5 microliter/hr) was infused into male SHR starting at 7 weeks of age. Four weeks later systolic blood pressure was only 157 +/- 3.3 compared to 181 +/- 3.9 mm Hg in vehicle-infused controls, and the pressor effect of ICV-injected angiotensin I was attenuated by 50%. When the same dose of captopril was infused intravenously, hypertension progressed as in vehicle-treated rats. Serum angiotensin-converting enzyme activity (SACE) and plasma arginine vasopressin (AVP) concentration were significantly higher (p less than 0.001 and 0.05, respectively), in the ICV captopril group than in the ICV vehicle group, while plasma aldosterone concentration and renin activity, fluid intake, urine volume, and urinary sodium excretion were similar in the two groups. Peripheral sympathetic nervous system activity assessed in the resting state was not altered by captopril treatment. In addition, AVP content of the telencephalon, diencephalon, mesencephalon, and pons medulla were not altered by ICV captopril. Renin activity was elevated in the telencephalon of ICV captopril-treated animals but unaltered in the other brain regions examined. These data demonstrate that ICV administration of captopril attenuates the development of hypertension in young SHR by mechanisms apparently independent of altered fluid and sodium balance and the sympathoadrenal system. The effect on blood pressure occurs in the absence of changes in renin activity or AVP content of plasma or those brain regions most often associated with blood pressure control.
Decrease in Na+,K+-ATPase activity and [3H]ouabain binding sites in sarcolemma prepared from hearts of spontaneously hypertensive rats.
Authors: Lee S W , Schwartz A , Adams R J , Yamori Y , Whitmer K , Lane L K , Wallick E T
Published: June 2012

Na+,K+-ATPase activity, phosphorylation, and [3H]ouabain binding in sarcolemma isolated from spontaneously hypertensive rat (SHR) hearts were compared to the same parameters in sarcolemma from normotensive rat (WKY) hearts. Sarcolemma prepared from SHR heart contained significantly less ouabain-inhibitable ATPase activity than sarcolemma from WKY heart. No significant differences in sarcolemmal protein content or recovery were noted between the two groups. The numbers of phosphorylation sites and ouabain binding sites were lower for SHR hearts than for WKY hearts. The KD values for ouabain binding were the same (0.30 muM) in cardiac sarcolemma of SHR and WKY. The I50 values for inhibition by ouabain of Na+,K+-ATPase were also the same for both groups (SHR = 49 microM; WKY = 44 microM). These data suggest that the decrease of cardiac sarcolemmal Na+,K+-ATPase activity in SHR hearts is due to a decrease in the number of active sites.
Regional vascular capacitance in rabbit one-kidney, one clip hypertension.
Authors: Ackermann U , Tatemichi S R
Published: June 2012

One-kidney Goldblatt hypertensive rabbits (New Zealand White) were studied after durations of renal artery clipping that varied from 6 to 17 days. Measurements included arterial pressure (ABP), iliac venous pressure (IVP), left atrial pressure (LAP), cardiac output (CO) (by thermodilution), blood volume (BV), cardiopulmonary volume (CPV), and hindleg thermodilution volume (HLV). These were determined at steady-state as well as during acute blood volume expansion. In sham-clipped animals, ABP was 74 +/- 1 mm Hg. This increased to 92 +/- 3 mm Hg by 6 to 9 days post-clipping, to 96 +/- 3 mm Hg by 10 to 13 days, to 89 +/- 4 mm Hg by 14 to 17 days. CO remained near 150 ml/min . kg until Day 13 and fell to 127 +/- 8 ml/min . kg at 14 to 17 days because of a fall in heart rate. Blood volume and stroke volume did not change significantly from 62 +/- 1 ml/kg and 0.60 +/- 0.04 ml/kg, respectively. The development of hypertension was due entirely to changes in peripheral resistance. CPV was 8.5 ml/kg initially and increased significantly as hypertension developed. HLV did not change significantly from about 10 ml/kg. During acute blood volume expansion, hypertensive animals showed smaller transient increases in CO than did sham-clipped normotensives, but the associated blood pressure rise was greater. This reduced vasodilator capacity was accompanied by reduced distensibility of the cardiopulmonary bed. In sham-clipped animals, the cardiopulmonary pressure/volume slope was between 0.05 and 0.07 mm Hg per ml/kg. This increased to 0.44 mm Hg per ml/kg by 14--17 days of clipping. The corresponding value for the hindleg region did not change significantly from 0.2 mm Hg per ml/kg. Cardiac output and stroke volume were directly correlated with cardiopulmonary volume. The slope of this correlation decreased significantly during hypertension. The data suggest that decreased cardiopulmonary compliance in hypertension minimizes transient changes in cardiac output. This is especially important for arterial blood pressure control in view of the impaired vasodilator capacity of the hypertensive circulation.
Baroreflex function in elderly hypertensives.
Authors: McGarry K , Laher M , Fitzgerald D , Horgan J , O'Brien E , O'Malley K
Published: June 2012

Baroreflex function was assessed in elderly hypertensive patients and compared with that observed in young hypertensives and young normotensives. Mean arterial pressure was reduced by 20% using intravenous nitroprusside infusion in 10 elderly hypertensive patients (older than 65 years and diastolic pressures over 95 mm Hg), in 10 young hypertensives (under 60 years and diastolic pressures over 95 mm Hg), and in seven young normotensive subjects (under 60 years and diastolic pressures under 95 mm Hg). Elderly subjects demonstrated greater sensitivity (p less than 0.005) and greater variability of response (p less than 0.025) to nitroprusside than either young group. There was no significant difference between the slight heart rate increases observed in the supine position in the three groups. However, in the erect position, heart rate increases were significantly less in the elderly hypertensive group than in the young hypertensive group (p less than 0.01) or the young normotensive group (p less than 0.005). Furthermore, the slope of the regression line relating change in blood pressure with change in R-R interval was less for the elderly patients than for the young hypertensives (p less than 0.05) or the young normotensives (p less than 0.025). We conclude that the heart rate component of the baroreflex is impaired in elderly hypertensives, and anticipate that the clinical response to antihypertensive drugs will be altered.
Influence of yohimbine on blood pressure, autonomic reflexes, and plasma catecholamines in humans.
Authors: Goldberg M R , Hollister A S , Robertson D
Published: June 2012

We studied the influence of the alpha 2-adrenoreceptor-blocking drug, yohimbine, on blood pressure, plasma norepinephrine, and other measures of autonomic function in normal male volunteers. These studies were designed to evaluate the role of alpha 2-receptors in the tonic regulation of sympathetic outflow in humans. In a dose-ranging study, we found that yohimbine HCl (0.016-0.125 mg/kg) elicited dose-related rises in mean, systolic, and diastolic pressures. At the maximal dose used (0.125 mg/kg), respective increments in mean, systolic, and diastolic pressures were 14 +/- 1 torr; 28 +/- 3 torr; and 8 +/- 1 torr (p less than 0.01) (mean +/- SE). No significant changes in heart rate occurred. Associated with the rise in blood pressure were enhanced pressor and heart rate responses to the cold pressor, isometric handgrip, and Valsalva maneuvers. In a double-blind study, yohimbine (0.125 mg/kg bolus, 0.001 mg/kg/min infusion) induced a two-to-threefold rise in plasma norepinephrine (p less than 0.01), without significantly altering plasma epinephrine or plasma renin activity. Ex vivo platelet aggregation in response to epinephrine was inhibited during yohimbine, showing that non-innervated alpha 2-adrenoreceptors were inhibited. Central effects of yohimbine were evaluated through use of linear analog mood rating scales which showed a shift from calm toward excited ends of these scales. If yohimbine is acting through blockade of alpha 2 receptors, then these receptors tonically suppress sympathetic outflow in humans.
Alcohol consumption as a risk factor for high blood pressure. Munich Blood Pressure Study.
Authors: Cairns V , Keil U , Kleinbaum D , Doering A , Stieber J
Published: June 2012

The Munich Blood Pressure Study (MBS), a 1980-81 cross-sectional study (with follow-up) of a random sample of 3198 Munich citizens aged 30-69 years (response rate 69%), revealed hypertensive blood pressure (BP) values in 17.7% of men and 10.7% of women (WHO criteria). One of the main goals of the MBS was to search for social, behavioral, and environmental risk factors for hypertension. The relationship between BP and five possible risk factors--alcohol consumption (g/day), cigarette smoking, oral contraceptive use, years of education, obesity (BMI)--has been examined. The major emphasis of this report is the relationship of alcohol consumption to BP. Multiple linear and logistic regression analyses were run controlling for both age and sex. All second- and third-order interactions between the independent variables were tested during a backward-stepping procedure. Alcohol consumption appeared as a significant main effect in many of the analyses. The coefficient of the alcohol variable ranged from 0.02 to 0.06 for men and women in the separate linear regression analyses for systolic and diastolic BP. Thus, for example, according to the model, the daily consumption of 1 liter of beer (40 g alcohol) may cause an increase in diastolic BP in women of 2.4 mm Hg.
Three red cell sodium transport systems in hypertensive and normotensive Utah adults.
Authors: Smith J B , Ash K O , Hunt S C , Hentschel W M , Sprowell W , Dadone M M , Williams R R
Published: June 2012

Sodium-lithium countertransport (SLC), sodium-potassium cotransport (CoT), and ouabain binding to sodium-potassium adenosine triphosphatase (Na, K-ATPase) sites were measured on fresh erythrocytes from hypertensive and normotensive Utah subjects with and without a first-degree relative with hypertension. SLC was measured as Li+ efflux into NaCl and MgCl2 media from Li+-loaded cells (5-7 mM). CoT was measured by monitoring Na+ and K+ efflux from cells loaded to 20-30 mM Na+ and 20-30 mMK+. Ouabain binding was determined for fresh cells using 3H-ouabain. Subjects were selected from pedigrees that showed a prevalence of hypertension. SLC was significantly elevated in 26.5% of the hypertensive subjects (p less than 0.001) as well as in 12.8% of the normotensives with a hypertensive first-degree relative (p less than 0.05). Although elevated SLC and decreased CoT have previously been associated with hypertension, no hypertensive subject in this study exhibited both abnormalities. All subjects with elevated SLC had normal CoT. A positive correlation between SLC and CoT was observed. Few hypertensive subjects (11.8%) had decreased CoT. In the majority of subjects studied, both SLC and CoT were normal: hypertensives 61.8%, normotensives with a hypertensive first-degree relative 61.7%, and other normotensives 58.7%. The number of ouabain-binding sites was not significantly altered among hypertensives, or their relatives, even though there was a positive correlation between SLC and the number of ouabain-binding sites.
Stability of blood pressure in vegetarians receiving dietary protein supplements.
Authors: Sacks F M , Wood P G , Kass E H
Published: June 2012

Vegetarians have relatively low blood pressure (BP) levels and consume less protein than do nonvegetarians , and there have been suggestions that certain proteins may raise BP. To determine whether dietary protein supplements raise the BP of vegetarians, 58 g/per day of a 60:40 mixture of soy and wheat proteins and an isocaloric low protein supplement supplying 7 g/day of rice protein were added for 6-week periods to the diet of 18 vegetarians in a 2-group crossover design. Mean daily protein intake during consumption of the low and high protein supplements was 63 and 119 g, respectively. Mean BP was 109/72 mm Hg after the high protein and 108/71 mm Hg after the low protein diet. Consumption of other major nutrients, mean body weight, and sodium and potassium excretion did not change significantly. Thus, protein supplementation of a vegetarian diet that contained a below average but nutritionally adequate amount of protein did not significantly affect BP over 6 weeks.
Hemodynamic effects of chronic alteration in hematocrit in spontaneously hypertensive rats.
Authors: Susic D , Mandal A K , Kentera D
Published: June 2012

This study describes the effect of a chronic decrease in hematocrit on blood pressure, cardiac output (CO), total peripheral resistance (TPR), and plasma volume in spontaneously hypertensive rats (SHR), and all but plasma volume in normotensive Wistar rats (NWR). Hematocrit was decreased by treatment with either heparin, vitamin K inhibitor ( pelentan ), or by repeated blood letting (BL). The results show that in SHR, a decrease in hematocrit, regardless of how produced, was associated with a significant decrease (p less than 0.01) in blood pressure. Prevention of heparin-induced decrease in hematocrit by repeated transfusions of red blood cells abolished the blood-pressure-lowering effect of heparin. By using combined data on hematocrit and systolic blood pressure in all five SHR groups, a significantly positive correlation and linear regression between hematocrit and blood pressure were obtained. When compared to control untreated SHR, heparin- or pelentan -treated SHR showed a significant (p less than 0.001) decrease in TPR and a significant increase in CO, while in SHR BL, no difference in TPR or CO was found. Plasma or blood volume did not differ among the groups. In NWR, heparin treatment resulted in significantly decreased hematocrit, decreased TPR, and increased CO compared to control normotensive rats. However, blood pressure did not change. Results confirming the authors' previous study and those of other investigators indicate a direct association between hematocrit and systemic hypertension. Lowering the hematocrit can effectively lower an elevated blood pressure. Moreover, the data suggest that heparin or pelentan induces a vasodilator effect that cannot be attributed to a decrease in hematocrit alone.
Erythrocyte cation cotransport and countertransport in essential hypertension.
Authors: Wiley J S , Clarke D A , Bonacquisto L A , Scarlett J D , Harrap S B , Doyle A E
Published: June 2012

We studied erythrocyte cation cotransport and countertransport systems in 21 and 27 patients with essential hypertension, respectively, all of whom were under 50 years of age, had a diastolic blood pressure level greater than 100 mm Hg, and had a family history of hypertension. The following parameters were normal in nearly all patients: total erythrocyte Na+ and K+ concentrations, the maximal rate (Vmax) of inward cotransport, the affinity of cotransport with Rb+ as the substrate, the net outward cotransport of Na+ ions, the passive "leak" influx of Rb,+ and the maximal rate of Li+-Na+ countertransport. Only four patients gave clearly abnormal results; in two the maximal rate of both cotransport and countertransport was double the normal values, while another two patients demonstrated a greater than twofold increase in passive "leak" influx to Rb+ ions. Most of the patients with moderate to severe essential hypertension in this Australian study were characterized by normal erythrocyte cation fluxes, but a few showed elevation of both cotransport and countertransport of cations.
Isoelectric focusing patterns of urinary kallikrein in Dahl salt-hypertension susceptible and resistant rats.
Authors: Rapp J P , McPartland R P , Batten C L
Published: June 2012

Dahl salt-sensitive (S) rats which are susceptible to hypertension have lower urinary kallikrein excretion than salt-resistant (R) rats which are not susceptible. Some physicochemical characteristics of partially purified urinary kallikrein were compared between the S and R strains. The isoelectric focusing pattern of S kallikrein was shifted so that a higher proportion of enzyme was present in isoelectric forms that had higher pI values compared to the pattern for R kallikrein. This strain difference was unique to urinary kallikrein; it was not seen in kallikrein extracted from salivary glands. The isoelectric focusing pattern for R urinary kallikrein could be converted to an S-type pattern by treatment with neuraminidase, which suggests that the differing isoelectric focusing patterns arose from differences in the sialic acid content of the kallikrein. The S kallikrein was slightly more heat-labile than R kallikrein, which was also compatible with the lower sialic acid content of the S enzyme. Tests involving the active site of the enzyme (Km values, pH curves, and heat of activation) were identical for the S and R strains. It was concluded that the structural differences observed in urinary kallikrein between S and R strains were compatible with strain-specific posttranslational processing of the enzyme.
Adrenal steroid responses to ACTH in glucocorticoid-suppressible aldosteronism.
Authors: Ganguly A , Weinberger M H , Guthrie G P , Fineberg N S
Published: June 2012

To investigate adrenal responses to adrenocorticotrophin (ACTH), we infused graded doses of ACTH (1.25 to 20.0 mIU/30 minutes) in normal subjects, patients with low-renin essential hypertension (LREH), primary aldosteronism (PA), and glucocorticoid-suppressible hyperaldosteronism (GSH). Plasma aldosterone, cortisol, corticosterone, and 18-hydroxycorticosterone were measured. The results revealed a greater increase in the plasma aldosterone and 18-hydroxycorticosterone levels evoked by ACTH in the GSH group than in any other group, which suggested enhanced responsiveness of the aldosterone-producing cells to ACTH and a probable adrenal abnormality.
Sympathetic activity and cardiac adrenergic receptors in one-kidney, one clip hypertension in rats.
Authors: Vlachakis N D , Ransom F , Kogosov E , Woodcock E , Alexander N , Maronde R F
Published: June 2012

The activity of the sympathetic nervous system, as measured by levels of plasma and cardiac catecholamines and catecholamine metabolites and the function of cardiac alpha- and beta-adrenergic receptors, was evaluated at 3 days and 4 weeks after induction of one-kidney, one clip hypertension (1K1C) in the rat. At 3 days, the plasma level of norepinephrine (NE) was lower in the 1K1C group than the control group (p less than 0.01), whereas epinephrine (E) and the metabolites dihydroxymandelic acid (DOMA), dihydroxyphenylglycol (DOPEG), and normetanephrine (NMN) were similar in both groups. In addition, cardiac content of catecholamines, their metabolites, and adrenergic receptors were similar in both groups. At 4 weeks, plasma levels of NE and DOPEG were lower (p less than 0.01), whereas levels of DOMA and NMN were higher (p less than 0.02 and p less than 0.001, respectively) in the 1K1C group than the control group. Cardiac content of NE (p less than 0.01), and DOPEG (p less than 0.05) was significantly lower, whereas DOMA and NMN were significantly higher (p less than 0.01) in the 1K1C group as compared to controls. In addition, cardiac density of both alpha- and beta-adrenergic receptors was reduced in the 1K1C group, whereas receptor affinities were unchanged.(ABSTRACT TRUNCATED AT 250 WORDS)
Interrelationships between blood pressure, sodium, potassium, serum cholesterol, and protein intake in Japanese.
Authors: Kihara M , Fujikawa J , Ohtaka M , Mano M , Nara Y , Horie R , Tsunematsu T , Note S , Fukase M , Yamori Y
Published: June 2012

Interrelationships among blood pressure (BP), sodium (Na), potassium (K), dietary protein, and serum cholesterol level (Chol) were examined in 62% (1120) of 1818 Japanese inhabitants of both sexes aged over 30 years who lived in a rural village in Japan. Fasting single-spot urine specimens were collected in the morning to measure Na, K, urea nitrogen (UN), inorganic sulfate (SO4), and creatinine (Cr). The Cr ratios of Na, K, UN, SO4, Na/K, and SO4/UN were analyzed by multiple regression analysis to determine independent associations with BP together with age, obesity index, hematocrit (Hct), Chol, triglyceride (TG), and fasting serum glucose level (Glu). Except for Na/Cr in men, Na/Cr and Na/K were found to be independently and positively related to BP, particularly to systolic BP (SBP). In contrast, K/Cr and SO4/UN (an index related to the dietary score of sulphur-containing amino acids derived mainly from animal protein) were both negatively associated with SBP, and UN/Cr (an index of total protein intake) was positively associated with SBP in men. Chol was linked to BP negatively in men but positively in women. Age, obesity index, TG, and Hct were generally positively and significantly related to BP in both sexes. The results confirmed on epidemiological grounds the positive link of Na and the negative link of K to BP within a single population in Japan. They further suggest, although only in men, that there is a negative relationship of Chol and dietary animal protein with BP.
Importance of dietary salt in the hemodynamic adjustment to weight reduction in obese hypertensive men.
Authors: Andersson O K , Fagerberg B , Hedner T
Published: June 2012

Twenty-three moderately obese middle-aged men with previously untreated hypertension (World Health Organization classification 1-2) were evaluated to assess the effects on blood pressure (BP) of a diet restricted in energy (fats and carbohydrates) but unrestricted in sodium (Group 1) compared to a diet restricted in energy and sodium (Group 2). The patients were randomly allocated to either of the two groups and were comparable in age, sex, weight, and BP. The same energy- and sodium- restricted diet was given to both groups, but the intake of Group 1 (n = 13) was supplemented with dietary sodium. The average urinary output for Group 1 was 192 +/- 39 mmol/24 hr at baseline and 200 +/- 56 mmol/24 hr during the diet. For Group 2 (n = 10), which remained on the initial diet, urinary sodium excretion changed from 188 +/- 53 mmol/24 hr at baseline to 97 +/- 32 mmol/24 hr (p less than 0.001). Intraarterial BP, cardiac output (CO), plasma volume, circulating norepinephrine (NE), and urinary NE were measured at baseline and at the end of the dieting periods. Before the dietary sodium supplement while on the initial diet, the patients in Group 2 showed a reduction in body weight from 97.3 +/- 10.5 kg to 88.6 +/- 9.9 kg (p less than 0.001). Heart rate (HR) and urinary NE output were significantly reduced in comparison with baseline, but intraarterial BP was unchanged. No change in cardiopulmonary blood volume, CO, or stroke volume (SV) was observed.(ABSTRACT TRUNCATED AT 250 WORDS)
Role of renal papillae in the regulation of sodium excretion during acute elevation of renal perfusion pressure in the rat.
Authors: Chen P S , Caldwell R M , Hsu C H
Published: June 2012

We studied the role of renal papillae in the mechanism of increased sodium excretion during acute increase in mean arterial pressure (MAP). Sodium excretion increased dramatically in normal rats after acute increase in MAP by epinephrine (E) infusion (0.4 micrograms/min/100g). Glomerular filtration rate (GFR), renal blood flow (RBF), and papillary plasma flow (PPF) remained unchanged after the E administration. To define the role of the medulla in the mechanism of pressure-induced natriuresis, experiments were performed in a group of rats 8 to 12 days after the development of papillary necrosis induced by bromoethylamine hydrobromide. Urinary sodium and fractional sodium excretions were 2.00 +/- 0.34 microEq/min and 2.37 +/- 0.53% (n = 7), respectively, in papillary necrosis rats infused with saline. Administration of E to papillary necrosis rats, however, failed to increase both urinary sodium (2.89 +/- 0.61 microEq/min) and fractional sodium (FENa, 2.82 +/- 0.63%, n = 6) excretions despite a marked increase in MAP (129 vs 150 mm Hg, p less than 0.01). The RBF increased slightly after E infusion (4.42 vs 3.24 ml/min/100 g, p less than 0.05), but the GFR was not different between the control (0.39 +/- 0.05 ml/min/100g, n = 7) and the E-treated rats (0.43 +/- 0.06, n = 6). Failure to increase sodium excretion during acute increase in MAP was not due to the decreased GFR, since control rats with bilateral partial nephrectomy were able to increase sodium excretion from 1.92 +/- 0.33 to 7.76 +/- 1.63 microEq/min (p less than 0.01) after E infusion. These findings, therefore, suggest that renal papillae play a major role in the mechanism of natriuresis during acute increase in MAP.
Central effect of intravenous phenylephrine on baroreflex control of renal nerves.
Authors: Imaizumi T , Brunk S D , Gupta B N , Thames M D
Published: June 2012

Responses of renal sympathetic nerve activity were determined in eight chloralose-anesthetized rabbits during sustained (1-3 minutes) increases in arterial pressure induced by phenylephrine infusion, and as arterial pressure returned to control. In four of the eight experiments, aortic baroreceptor traffic was also recorded. When arterial pressure was raised from 81 +/- 5 to 110 +/- 7 mm Hg, renal nerve activity decreased from 30 +/- 7 to 1 +/- 1 imp/sec. Aortic nerve activity increased from 208 +/- 35 to 346 +/- 49 imp/sec. When pressure returned to control (81 +/- 5 mm Hg), renal nerve activity remained inhibited (7 +/- 2 imp/sec), even though aortic nerve activity had also returned to control (195 +/- 33 imp/sec). Arterial pressure and traffic in the renal and aortic nerves returned to control over the succeeding 1 to 5 minutes. Transient increases in arterial pressure (lasting less than 1 minute) due to bolus injections of phenylephrine resulted in inhibition of renal nerve traffic followed by rapid recovery. In five rabbits with aortic and vagal nerves sectioned and both carotid sinuses isolated from the circulation, intravenous phenylephrine infusion augmented the gain of the isolated carotid baroreflex (particularly at low carotid sinus pressures). In nine experiments, injection of phenylephrine (0.01, 0.1, or 1.0 microgram) into the lateral ventricles did not change the basal renal nerve traffic but augmented the gain of the baroreflex control of the renal nerves. Our data indicate that peripherally infused phenylephrine can alter the arterial baroreflex control of the renal nerves by a central effect. The similar influence of intracerebroventricular phenylephrine on baroreflex control of the renal nerves is consistent with this view.
Age-related changes of baroreflex function, plasma norepinephrine, and blood pressure.
Authors: Shimada K , Kitazumi T , Sadakane N , Ogura H , Ozawa T
Published: June 2012

Interrelationships between age, baroreflex sensitivity, plasma norepinephrine levels, and systolic blood pressure were assessed in a group of 54 normal subjects ranging in age from 14 to 77 years. Baroreflex sensitivity was measured by the change in R-R intervals per unit change in systolic blood pressure during phase 4 of the Valsalva maneuver. All correlations among these four variables were statistically significant (p less than 0.05 or 0.01). To investigate possible causal relationships between age-related changes of baroreflex sensitivity, plasma norepinephrine levels, and blood pressure, partial correlative analysis was then performed. After the effect of age was eliminated, plasma norepinephrine levels were found to be related positively to blood pressure (r = 0.29, p less than 0.05) and negatively to baroreflex sensitivity (r = -0.34, p less than 0.05). The increase in plasma norepinephrine levels could be causally related to the elevation of blood pressure, as plasma norepinephrine levels could provide an index of sympathetic activity. Furthermore, baroreflex sensitivity was found to be negatively related to age (r = -0.44, p less than 0.01) independent of plasma norepinephrine levels, whereas plasma norepinephrine levels were no longer related to age (r = 0.10) after adjusting for the effect of baroreflex sensitivity. This finding suggests that an increase in plasma norepinephrine levels with age could be mediated by the age-related change of baroreflex sensitivity.(ABSTRACT TRUNCATED AT 250 WORDS)
Factors that influence stroke in Dahl salt-sensitive rats.
Authors: Werber A H , Baumbach G L , Wagner D V , Mark A L , Heistad D D
Published: June 2012

Japanese rat chow and cerebral sympathetic denervation increase the incidence of stroke in stroke-prone spontaneously hypertensive rats. The purpose of this study was to determine if Japanese rat chow and sympathetic denervation would result in a high incidence of stroke in Dahl salt-sensitive (DS) rats, which have not been reported to be stroke prone. At 3 to 4 weeks of age, DS rats of both sexes began consumption of a high salt Japanese or American chow and underwent unilateral superior cervical sympathetic ganglionectomy. The rats fed American chow were found to have a high incidence of stroke (46%). Rats fed Japanese chow had shorter survival and a higher incidence of stroke (78%) than rats fed American chow (p less than 0.05). Blood pressure increased faster in DS rats fed Japanese chow (p less than 0.05). Metabolic studies indicated that increased sodium consumption accounted for only part of the acceleration of hypertension by Japanese rat chow. In DS rats grouped for equal levels of blood pressure, those fed Japanese chow had modestly reduced survival (p less than 0.05) compared with those fed American chow and had a greater incidence of stroke (85% vs 38%; p less than 0.05). Location of stroke was not influenced by removal of sympathetic nerves.(ABSTRACT TRUNCATED AT 250 WORDS)
Ouabain binding and Na+ content in resistance vessels and skeletal muscles of spontaneously hypertensive rats and K+-depleted rats.
Authors: Aalkjaer C , Kjeldsen K , Nørgaard A , Clausen T , Mulvany M J
Published: June 2012

The possible role of Na+ in the development of hypertension in rats was explored in measurements of intracellular Na+, 22Na efflux, and 3H-ouabain binding sites in resistance vessels and skeletal muscles. In resistance vessels obtained from 13-week-old spontaneously hypertensive rats (SHR) or age-matched Wistar-Kyoto rats (WKY), (Na)i, total or ouabain-resistant 22Na efflux, and the concentration of 3H-ouabain binding sites showed no significant differences. Soleus muscles obtained from 6-week-old and 13-week-old SHR contained 5 to 11% more 3H-ouabain binding sites than those of WKY. The small difference in ouabain binding probably was related more to variations in growth rate and strain than to the hypertension. In SHR and WKY the Na+ and K+ contents of gastrocnemius muscles were almost identical at 6 and 13 weeks of age. By contrast, in Wistar rats in which the (Na)i of skeletal muscle was increased sixfold by K+ depletion, the systolic blood pressure was decreased by 10%. The K+ depletion was associated with a 35 to 55% decrease in the concentration of 3H-ouabain binding sites in both resistance vessels and skeletal muscles. The results provide no support for any simple cause-effect relationships between either elevated (Na)i or altered concentration of 3H-ouabain binding sites and hypertension in SHR.
Longitudinal study of salt preferences in normotensive and hypertensive rats.
Authors: Ferrell F , Gray S D
Published: June 2012

To determine whether age-related changes in salt preferences occur over the lifespans of spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY), the same animals of each genotype were tested as juveniles, and as young and older adults. Taste preference ratios for NaCl and KCl, at concentrations from 0.001 to 1.0 M, were calculated using 24-hour, two-bottle preference tests of each salt versus distilled water. Genotype exerted a significant effect on preference for both NaCl and KCl (p less than 0.0005). At each age and across concentrations, SHR had consistently higher preferences than did WKY. Few marked, age-related changes in overall preference for NaCl were noted within either strain, but juvenile and older adult SHR and WKY exhibited stronger preferences than did young adults for the higher concentrations of NaCl below the rejection threshold (p less than 0.001). Statistical age by concentration preference trends for KCl were similar to those for NaCl in SHR. Young adult WKY, however, had a significantly lower rejection threshold for that compound than did juveniles and older adults (p less than 0.001). These results indicate that genotype, age, salt type, and salt concentration can interact to influence salt preference in hypertension.
High sodium intake enhances renal nerve and antinatriuretic responses to stress in spontaneously hypertensive rats.
Authors: Koepke J P , DiBona G F
Published: June 2012

The effects of high sodium intake (drinking 0.9% NaCl for 15 days) on the increased renal sympathetic nerve activity and decreased urinary sodium excretion resulting from stressful environmental stimulation (air jet to head) were examined in conscious spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto rats (WKY). On a normal sodium intake in SHR, air stress increased renal sympathetic nerve activity 77% and decreased urinary sodium excretion 28% without altering effective renal plasma flow or glomerular filtration rate. By contrast, in conscious SHR on high sodium intake, the same air stress caused a greater increase in renal sympathetic nerve activity (103%) and a greater antinatriuresis (42%) along with reductions in effective renal plasma flow and glomerular filtration rate. Surgical renal denervation prevented the antinatriuretic responses to air stress in other conscious SHR on high or normal sodium intake. In conscious WKY, air stress had no effect on renal sympathetic nerve activity or urinary sodium excretion, regardless of normal or high sodium intake. We conclude that the enhanced renal sympathetic nerve activity and antinatriuretic responses to air stress in conscious SHR on high sodium intake are dependent on a centrally mediated facilitation of sympathetic neural outflow to the kidney. The greater antinatriuretic response to air stress in conscious SHR than in WKY may reflect a greater genetic predisposition in SHR to increase renal sympathetic nerve activity during air stress.
Effects of a calcium entry blocker on blood pressure and renal function during angiotensin-induced hypertension.
Authors: Huelsemann J L , Sterzel R B , McKenzie D E , Wilcox C S
Published: June 2012

The effects of the calcium entry blocker nitrendipine on blood pressure (BP) and renal hemodynamics were studied in rats with angiotensin II (ANG II)-induced hypertension. The ANG II was infused subcutaneously by implanted osmotic minipumps for 14 to 16 days. There was a progressive rise in BP in ANG II-infused rats to levels 58 mm Hg above basal by Day 10, whereas control rats with sham pumps remained normotensive. Nitrendipine or vehicle was administered by gavage to groups of control and hypertensive rats for 5 days, and clearance experiments were performed with the rats under anesthesia on the last day. The prolonged infusion of ANG II increased the renal vascular resistance and reduced the glomerular filtration rate and renal Na+ excretion. At a dose of 3 mg/100 g body weight, nitrendipine had no consistent effects on BP or renal function of control rats. By contrast, in rats with ANG II-induced hypertension, nitrendipine normalized both the BP and the changes in renal vascular resistance and glomerular filtration rate. Despite the fall in BP, nitrendipine caused a marked diuresis and natriuresis. Moreover, nitrendipine increased Na+ excretion of conscious, ANG II-hypertensive rats but not of controls. Thus, nitrendipine appears to be highly effective in reversing ANG II-induced hypertension and Na+ retention. These findings also indicate that the hypertension, renal vasoconstriction, and Na+ retention accompanying prolonged ANG II infusions may be mediated by calcium-dependent mechanisms.
Renal and blood pressure responses to synthetic atrial natriuretic factor in spontaneously hypertensive rats.
Authors: Marsh E A , Seymour A A , Haley A B , Whinnery M A , Napier M A , Nutt R F , Blaine E H
Published: June 2012

Atrial natriuretic factor (ANF) is a potent natriuretic and vasorelaxant agent that also stimulates guanosine 3',5'-cyclic monophosphate (cGMP) excretion in normotensive animals. These properties suggest that ANF may be involved in the regulation of blood pressure. To test a pure preparation of ANF in both normotensive and hypertensive animals, a synthetic 26 amino acid peptide (sANF) contained within endogenous rat ANF was infused intravenously into conscious Wistar-Kyoto rats (WKY) and spontaneously hypertensive rats (SHR) at doses from 12 to 190 pmol/minute. Mean arterial pressure fell progressively as doses of sANF were increased until maximum responses of -41 +/- 5 mm Hg and -29 +/- 5 mm Hg were obtained during infusion of 95 pmol/minute sANF in SHR and WKY, respectively. Heart rate was not significantly affected in either group. At sANF doses of 12 to 50 pmol/minute, urinary electrolyte excretion rose in a dose-related fashion and was similar in WKY and SHR. At infusions of 95 to 190 pmol/minute, the diuretic and saluretic responses were diminished in the hypertensive animals. Only the 190 pmol/minute sANF dose significantly enhanced cGMP excretion in SHR (p less than 0.05); however, in WKY urinary cGMP excretion was elevated in a dose-related fashion. At the highest sANF dose, cGMP excretion was approximately 15 times that observed in the pretreatment urine. The differences in the renal and blood pressure responses to sANF in SHR and WKY suggest that the actions of endogenous ANF may be altered in hypertension.
Diet, blood pressure, and multicollinearity.
Authors: Reed D , McGee D , Yano K , Hankin J
Published: June 2012

Recent reports of an inverse association between dietary calcium intake and hypertension stimulated this analysis of the relationship of blood pressure to more than 20 dietary factors among a group of 8000 Japanese men in Hawaii. Reported intakes of potassium, calcium, protein, and milk were all inversely associated with blood pressure levels when examined one at a time while controlling for other risk factors. Alcohol intake was directly associated with blood pressure, and was treated as a confounding variable in the analysis. The association of potassium intake with blood pressure was relatively stronger than the associations for other nutrients, but the intake of potassium was so highly correlated with intakes of calcium, milk, and protein that it was not statistically possible to identify the independent association of potassium and blood pressure. Calcium intake was strongly correlated with milk and potassium intakes, and only calcium from dairy sources was associated with blood pressure. These data thus indicate that several dietary factors are inversely related to blood pressure levels independently of other risk factors such as age, body mass, and alcohol intake. The high degree of intercorrelation (multicollinearity) among these dietary factors, however, indicates that the independent role of any specific nutrient cannot be conclusively separated from the possible effects of other nutrients in this type of study.