Dietary factors in the pathogenesis and treatment of hypertension

Associations of Systematic Inflammatory Markers with Diet Quality, Blood Pressure, and Obesity in the AIRWAVE Health Monitoring Study

Introduction

Chronic low-grade inflammation is a characteristic feature of obesity, and elevated levels of inflammation are associated with pathophysiologic consequences and a constellation of metabolic disturbances, such as hypertension. The relationships of inflammation with diet, obesity, and hypertension are complex, hence, this study aimed to assess cross-sectional relationships between inflammatory scores, diet quality, obesity, high blood pressure (BP), and hypertension in the Airwave Health Monitoring Study cohort, a large cohort of police officers and police staff in the United Kingdom.

Methods

Data from 5198 men and 3347 women who completed health screening measurements and dietary assessment between 2007 and 2012 were included (n=8545 adults). Platelet-to-lymphocyte ratio (PLR), neutrophil-to-lymphocyte ratio (NLR), lymphocyte-to-monocyte ratio (LMR), and the systemic immune-inflammation index (SII) were calculated. Diet quality was evaluated using the Nutrient-Rich Food 9.3 (NRF9.3) index score.

Results

Results show that a 1SD higher diet quality score, waist circumference, and systolic/diastolic BP were significantly associated with SII differences of -33.3 (95% confidence interval (CI): -49.0, -17.6), 8.2 (95% CI: 0.2, 16.6), 17.9 (95% CI: 10.1, 25.8), and 18.3 (95% CI: 10.8, 25.7) (Model 2; P<0.0001), respectively. A 1SD higher diet quality score, waist circumference, and BMI were also significantly associated with PLR (P<0.0001). The odds of elevated PLR were higher in those with higher systolic and diastolic BP (P<0.0001, P=0.0006, respectively).

Conclusion

In conclusion, the findings of this analysis add to the existing knowledge indicating a link between inflammation and conditions such as obesity, hypertension, and behavioral factors including diet quality. Of the various inflammatory scores evaluated, SII and PLR were consistently significantly associated with diet quality and these conditions.

UPLC-QToF Nanospray MS and NMR Analysis of Ficus sycomorus Stem Bark and Its Effects on Rabbit

In the present study, a phytochemical of Ficus sycomorus (Moraceae family) was screened, and the effect of this extract on rabbit performance indices, immunity, and carcass quality measures was determined. Ficus sycomorus samples were collected, air-dried, and extracted with 70% methanol to prepare a solution of 100 mg/mL concentration. The extract was subjected to high-resolution mass spectrometric measurements via ultra-high performance liquid chromatography-quadrupole time-of-flight-nanospray mass spectrometry (UPLC-QToF-MS) and 1H NMR analysis. Forty-eight male rabbits, one-month-old, belonging to the Blanc de Bouscat and New Zealand White breeds were selected and distributed equally in a 2 × 3 factorial trial. The rabbits within each breed received F. sycomorus extract at the dose of 0, 100, and 200 mg/kg for 60 days. Blood samples were collected and serum obtained for the detection of liver enzymes, serum lipids, and proteins. The results of UPLC-QToF-MS and molecular networking analysis revealed the presence of procyanidin B2, procyanidin A1, genistein, eriodyctiol, catechin, luteolin, biochanin A, and chlorogenic acid that might exhibit various pharmaceutical activities. However, the F. sycomorus extract reduced rabbit performance indices and carcass quality measures. In addition, this extract significantly depressed the low-density lipoprotein and triglycerides, which may indicate the antidyslipidemia effect of this extract on rabbits.

The role of dietary salt and alcohol use reduction in the management of hypertension

Introduction: Despite the improved treatment protocol of hypertension, the magnitude of the disease and its related burden remains raised. Hypertension makes up the leading cause of stroke, kidney disease, arterial disease, eye disease, and cardiovascular disease (CVD) growth. Areas covered: This review provides the overview of the role of dietary salt and alcohol use reduction in the management of hypertension, a brief history of alcohol, the vascular endothelium functions, the effects of alcohol use on blood pressure (BP), the mechanisms of alcohol, brief history of salt, the effects of dietary salt intake on BP, and the mechanisms of salt. Expert opinion: Studies found that high dietary salt intake and heavy alcohol consumption have a major and huge impact on BP while both of them have been identified to increase BP. Also, they raise the risk of hypertension-related morbidity and mortality in advance. On the other way, the dietary salt and alcohol use reduction in the management of hypertension are significant in the control of BP and its related morbidity and mortality. Further, studies suggested that the dietary salt and alcohol use reductions are the cornerstone in the management of hypertension due to their significance as part of comprehensive lifestyle modifications.

Trace Element Determination and Cardioprotection of Terminalia pallida Fruit Ethanolic Extract in Isoproterenol Induced Myocardial Infarcted Rats by ICP-MS

The trace elements and minerals in Terminalia pallida fruit ethanolic extract (TpFE) were determined by the instrument inductively coupled plasma-mass spectrometry (ICP-MS), and the cardioprotection of TpFE against isoproterenol (ISO)-administered rats was studied. Rats were pretreated with TpFE (100, 300, and 500 mg/kg bw) for 30 days, with concurrent administration of ISO (85 mg/kg bw) for two consecutive days. The levels of trace elements and minerals in TpFE were below the permitted limits of World Health Organization standards. ISO administration significantly increased the heart weight and cardiac marker enzymes in serum, xanthine oxidase, sodium, and calcium in the heart, whereas significantly decreased body weight, reduced glutathione, glutathione-S-transferase, superoxide dismutase, and potassium in the heart. Oral pretreatment of TpFE significantly prevented the ISO-induced alterations. This is the first report that revealed the determination of trace elements and mineral nutrients of TpFE by ICP-MS which plays a principal role in the herbal drug discovery for the treatment of cardiovascular diseases.

Rat serum electrolytes, lipid profile and cardiovascular activity onNauclea latifolia leaf extract administration

Aqueous extract of the leaf and root ofNauclea latifolia Sm. (Rubiaceae) is used in Nigerian folk medicine for the treatment of hypertension. This work is carried out to investigate the effect ofNauclea latifolia leaf extract on lipid profile and cardiovascular activity of rats. Normal and 10% coconut oil fed rats were treated with the water-soluble fraction of the ethanol extract ofNauclea latifolia leaf for 2 weeks. Forty-eight mature male albino rats of the Wistar strain were divided into two experiments of four groups, each group having 6 animals. Experiment I animals were treated with the water-soluble fraction of the ethanol extract whilst experiment II animals were fed 10% coconut oil meal before treatment with the water-soluble fraction of the ethanol extract. A single oral dose ofNauclea latifolia was 170, 340 and 510 mg/kg body wt/day of the extracts respectively for 2 wks. There was no significant change in the lipid profile of the experimental animals as compared with the controls. There was about 40% relaxation on contracted thoracic aorta that was pre-contracted with 2 μM phenylephrine. The viability of the tissue was tested against 10 μM of acetylcholine. There was no significant (P>0.05) change in Na(+) concentration in the serum. However, the K(+) concentration in the serum of the experimental animals showed a significant increase. The study shows that ethanol extract ofNauclea latifolia has vasodilator action on the aorta and that lipid profiles of experimental rats were not affected. Furthermore, the increase in the K(+) may be contributing to the vasodilator effect ofNauclea latifolia.

The veterans' study to improve the control of hypertension (V-STITCH): design and methodology

BACKGROUND

Among the 60 million Americans with hypertension, only approximately 31% have their blood pressure (BP) under control (<140/90 mm Hg). Despite the damaging impact of hypertension and the availability of evidence-based target values for BP, interventions to improve BP control have had limited success.

OBJECTIVES

A randomized controlled health services intervention trial with a split-plot design is being conducted to improve BP control. This 4-year trial evaluates both a patient and a provider intervention in a primary care setting among diagnosed hypertensive veterans.

METHODS

In a cluster-randomization, 30 primary care providers in the Durham VAMC Primary Care Clinic were randomly assigned to receive the provider intervention or control. The provider intervention is a patient-specific electronically generated hypertension decision support system (DSS) delivering guideline-based recommendations to the provider at each patient's visit, designed to improve guideline-concordant therapy. For these providers, a sample of their hypertensive patients (n=588) was randomly assigned to receive a telephone-administered patient intervention or usual care. The patient intervention incorporates patients' need assessments and involves tailored behavioral and education modules to promote medication adherence and improve specific health behaviors. All modules are delivered over the telephone bi-monthly for 24 months. In this trial, the primary outcome is the proportion of patients who achieve a BP < or =140/90 mm Hg at each outpatient clinic visit over 24 months.

CONCLUSION

Despite the known risk of poor BP control, a majority of adults still do not have their BP controlled. This study is an important step in testing the effectiveness of a patient and provider intervention to improve BP control among veterans in the primary care setting.

Decreased endothelium-dependent NO-cGMP vascular relaxation and hypertension in growth-restricted rats on a high-salt diet

Low birth weight caused by placental insufficiency increases the risk of hypertension in young adults, particularly while ingesting a high-salt diet; however, the vascular mechanisms involved are unclear. We tested whether intrauterine fetal growth restriction results in salt-sensitive offspring that exhibit impaired endothelium-dependent relaxation, enhanced vascular contraction, and hypertension during high-salt diet feeding. Male offspring of control pregnant rats and pregnant rats with reduced uterine perfusion pressure (intrauterine growth restricted [IUGR]) were fed either a normal-sodium (NS, 1%) or a high-sodium (HS, 8%) diet. Body weight was less in IUGR/NS and IUGR/HS than in NS and HS rats. Arterial pressure was greater in IUGR/NS (144+/-4 mm|Hg) than in NS (131+/-3 mm|Hg) rats and far greater in IUGR/HS (171+/-12 mm|Hg) than in HS (129+/-2 mm|Hg) rats. In isolated, endothelium-intact aortic strips, phenylephrine (Phe, 10(-5) mol/L) caused an increase in active stress that was greater in IUGR/NS (13.9+/-0.9 N/m2) than in NS (8.5+/-0.6 N/m2) animals and far greater in IUGR/HS (18.2+/-1.2 N/m2) than in HS (9.4+/-0.8x10(4) N/m2) rats. Acetylcholine caused relaxation of the Phe-mediated contraction and induced vascular nitrite/nitrate production that was less in IUGR/NS than in NS animals and far less in IUGR/HS than in HS rats. N(G)-nitro-L-arginine methyl ester, which inhibits nitric oxide (NO) synthase, or ODQ, which inhibits cGMP production in smooth muscle, inhibited acetylcholine relaxations and enhanced Phe contractions in NS and HS rats but not in IUGR/NS or IUGR/HS rats. Endothelium removal enhanced Phe-induced stress in NS and HS rats but not in IUGR/NS or IUGR/HS rats. Thus, endothelium-dependent relaxation via the NO-cGMP pathway is inhibited in systemic vessels of IUGR rats, particularly during intake of an HS diet. This might explain the increased vasoconstriction and arterial pressure in low-birth-weight offspring during ingestion of an HS diet.

Hypertension is related to the degradation of dietary frying oils

BACKGROUND

The family kitchen resembles an uncontrolled laboratory experiment, and some discrepancies in the relation between the risk of hypertension and dietary fat may be partly due to the manipulation to which the fats were subjected.

OBJECTIVE

We investigated whether deterioration in the quality of the cooking oils in the family household contributes to the risk of high blood pressure.

DESIGN

The study was cross-sectional. Anthropometric measurements were obtained for 1226 persons aged 18-65 y who were selected randomly from the municipal census of Pizarra, Spain. An oral-glucose-tolerance test was given to 1020 of these persons. Samples of the cooking oil being used were taken from the kitchens of a random subset of 538 persons. The concentrations of polar compounds and polymers were used as markers of the deterioration of the oils. The strength of association between variables was measured by calculating the odds ratio from logistic models.

RESULTS

Hypertension was strongly associated with obesity and was influenced by sex, diabetes, and age. The presence of excess polar compounds in the cooking oil and the use of sunflower oil were related to the risk of hypertension, whereas the concentration of monounsaturated fatty acids in the serum phospholipids was negatively related to this risk. These associations remained after inclusion in the models of age, sex, obesity, and the presence of carbohydrate metabolism disorder.

CONCLUSIONS

The risk of hypertension is positively and independently associated with the intake of cooking oil polar compounds and inversely related to blood concentrations of monounsaturated fatty acids.

Endothelin-induced increases in Ca2+ entry mechanisms of vascular contraction are enhanced during high-salt diet

High-salt diet is often associated with increases in arterial pressure, and a role for endothelin (ET)-1 in salt-sensitive hypertension has been suggested; however, the vascular mechanisms involved are unclear. We investigated whether ET increases the sensitivity of the mechanisms of vascular contraction to changes in dietary salt intake. Active stress and 45Ca2+ influx were measured in endothelium-denuded aortic strips of male Sprague-Dawley rats not treated or chronically infused intravenously with ET (5 pmol/kg per minute) and fed either normal-sodium diet (NS, 1%) or high-sodium diet (HS, 8%) for 9 days. Phenylephrine (Phe) caused increases in active stress that were similar in NS and HS, but were greater in NS/ET (maximum, 10.5+/-0.7) than in NS (maximum, 7.4+/-0.9) rats, and further enhanced in HS/ET (maximum, 14.4+/-1.1) compared with HS rats (maximum, 8.0+/-0.8 x 10(4)N/m2). Phe was more potent in causing contraction in NS/ET than in NS rats and in HS/ET than in HS rats. In Ca2+-free (2 mmol/L EGTA) Krebs, stimulation of intracellular Ca2+ release by Phe (10(-5) mol/L) or caffeine (25 mmol/L) caused a transient contraction that was not significantly different in all groups of rats. In contrast, membrane depolarization by high-KCl solution, which stimulates Ca2+ entry from the extracellular space, caused greater contraction in ET-infused rats, particularly those on HS diet. Phe (10(-5) mol/L) caused an increase in 45Ca2+ influx that was greater in NS/ET (27.9+/-1.7) than in NS (20.1+/-1.8) rats and further enhanced in HS/ET (35.2+/-1.8) compared with HS rats (21.8+/-1.9 micromol/kg/min). The Phe-induced 45Ca2+ influx-stress relation was not different between NS and HS rats, but was enhanced in ET-infused rats particularly those on HS. The enhancement of the 45Ca2+ influx-active stress relation in ET-infused rats was not observed in vascular strips treated with the protein kinase C inhibitor GF109203X or calphostin C (10(-6) mol/L). Thus, low-dose infusion of ET, particularly during HS, is associated with increased vascular reactivity that involves Ca2+ entry from the extracellular space, but not Ca2+ release from the intracellular stores. The ET-induced enhancement of the Ca2+ influx-stress relation particularly during HS suggests activation of other mechanisms in addition to Ca2+ entry, possibly involving protein kinase C. The results suggest that ET increases the sensitivity of the mechanisms of vascular smooth muscle contraction to high dietary salt intake and may, in part, explain the possible role of ET in salt-sensitive hypertension.

Gender differences in vascular smooth muscle reactivity to increases in extracellular sodium salt

Hypertension is more common in men and postmenopausal women than in premenopausal women, and gender differences in sensitivity to high dietary Na(+) salt have been suggested; however, the vascular mechanisms involved are unclear. We investigated whether increases in the extracellular concentration of Na(+) ([Na(+)](e)) enhance the mechanisms of vascular smooth muscle contraction and whether the vascular effects of [Na(+)](e) exhibit gender differences. Isometric contraction and (45)Ca(2+) influx were measured in endothelium-denuded aortic strips that were isolated from intact male, intact female, castrated male, and ovariectomized (OVX) female Sprague-Dawley rats and incubated in Krebs' solution (2.5 mmol/L Ca(2+)) containing increasing [Na(+)](e) by the addition of 1, 3, 6, 10, 20, and 30 mmol/L NaCl. Increasing [Na(+)](e) for 30 minutes did not increase the resting tone or (45)Ca(2+) influx in any group of rats. Phenylephrine (Phe) caused concentration-dependent increases in contraction and (45)Ca(2+) influx. In vascular strips from intact males, increasing [Na(+)](e) by the addition of 1 to 6 mmol/L NaCl significantly increased the magnitude of Phe contraction and (45)Ca(2+) influx. Further increases in [Na(+)](e) by the addition of 10, 20, and 30 mmol/L NaCl increased Phe-induced (45)Ca(2+) influx but inhibited Phe contraction, possibly because of excessive increases in ionic strength. Preincubation with 2,4-dichlorobenzamil (10(-5) mol/L), inhibitor of the Na(+)-Ca(2+) exchanger, or KB-R7943 (10(-5) mol/L), selective inhibitor of the reverse mode of the Na(+)-Ca(2+) exchanger, abolished the increases in Phe contraction and (45)Ca(2+) influx at increasing [Na(+)](e) obtained by the addition of 1 to 6 mmol/L NaCl. Preincubation in Krebs' solution containing control [Na(+)](e) plus 1 to 6 mmol/L LiCl or N-methyl-D-glucamine did not increase Phe contraction. In intact females, the Phe contraction and Ca(2+) influx were less than those in intact males and were not enhanced with increases in [Na(+)](e). The enhancement of Phe contraction and Ca(2+) influx with increases in [Na(+)](e) were not significantly different between castrated male rats and intact male rats but were greater in OVX female rats than intact female rats. In OVX female rats or castrated male rats treated with 17beta-estradiol (but not 17alpha-estradiol) subcutaneous implants, no significant changes in Phe contraction or Ca(2+) influx with increases in [Na(+)](e) were observed. In OVX female or castrated male rats simultaneously treated with 17beta-estradiol plus the estrogen receptor antagonist ICI 182,780, the Phe contraction and Ca(2+) influx were enhanced with increases in [Na(+)](e). Thus, in intact male rats, small physiological increases in [Na(+)](e) enhance smooth muscle contraction to Phe by a mechanism involving Ca(2+) entry, possibly via the reverse mode of the Na(+)-Ca(2+) exchanger. This mechanism appears to be reduced in the presence of endogenous or exogenous estrogen and thereby protects female rats against excessive increases in vascular reactivity during high dietary Na(+) intake.

Role of weight loss and polyunsaturated fatty acids in improving metabolic fitness in moderately obese, moderately hypertensive subjects

OBJECTIVE

While the exact regulatory interactions between blood pressure (BP) and obesity are not completely understood, weight loss provides an alternative to pharmacological treatment of hypertension. The intent of this repeated measures study of mild-moderate hypertensive, moderately obese subjects (34 females/18 males) was to determine if the reduction in BP following weight loss could be further affected by modifying the fatty acid (FA) composition of the hypocaloric diet.

METHODS

BP, insulin sensitivity (Si), and lipid parameters were assessed before and after a 10-week calorie-restricted period. Subjects were randomized to one of three dietary groups differing in FA composition. Reduced body weight was maintained for a further 4 weeks and body composition assessment, BP and heart rate measurements were repeated.

RESULTS

Weight loss (10%) in obese hypertensive subjects resulted in substantial improvements in BP, Si and lipid profile. There was no additional effect on the reduction in BP by the type of FA consumed in the diet. Following weight loss, there was a trend for omega-3 FAs to have a protective effect on fat-free mass loss (compared to omega-6 FA Group and saturated FA Group) and a trend to further enhance Si. There were significant improvements in circulating lipid profiles independent of the dietary FA intervention following the weight loss. The improvements in BP and body composition were maintained during the weight-loss maintenance period. The type of fat consumed had minor differential effects on some of the measured metabolic outcomes.

CONCLUSION

These results provide strong support for modest weight loss as a treatment for hypertension.

A comparison of dietary and non-dietary factors of hypertension and normal blood pressure in a Chinese population

The aim of this study was to compare the differences of dietary and non-dietary factors in hypertension and normal blood pressure (BP) of Chinese urban people. Two cross-sectional population surveys were carried out in Tianjin, one of the three largest cities in China. A total of 2068 subjects aged 35-64 years were selected by a random stratified cluster sampling, 367 men and 395 women were hypertensive, and 623 men and 683 women had normal BP. The diet was assessed by food weighing plus consecutive individual 3-day food records. Health status, health behaviours and anthropomentry were assessed. The whole population had a high sodium and low potassium consumption level. Hypertensive men and women had significantly higher daily dietary sodium intake (P < 0.05) and hypertensive women had higher dietary sodium-to-potassium ratio (P < 0.01) than men and women with normal BP. Age, body mass index, overweight and family history of hypertension were positively related to high BP. dietary sodium intake and dietary sodium-to-potassium ratio were positively associated with high BP. Education level in women and commuting physical activity in men were inversely associated with high BP.

Dietary beliefs in the Baltic republics

OBJECTIVES

As beliefs and knowledge about the possible effects of foods on health can influence food behaviours, this study examined selected dietary beliefs in the Baltic countries and the association of beliefs related to salt intake and to types of fat with food behaviours.

DESIGN

A cross-sectional study.

SETTING

Data from three surveys conducted in Estonia, Latvia and Lithuania in the summer of 1997 were used to describe the prevalence of dietary beliefs in these countries and to investigate the association between beliefs and behaviours (using logistic regression).

SUBJECTS

Representative national samples of adults were selected in each country (Estonia, n = 2018; Latvia, n = 2308; Lithuania, n = 2153).

RESULTS

Misunderstood concepts (myths) related to dietary salt, types of fat, meat consumption and bread and potatoes were observed in high proportions of the population. Education level was an important correlate of beliefs related to salt intake and types of fat, people with a higher education level being more likely to be familiar with these issues. Correct beliefs were not consistently associated with healthier behaviours (e.g. less frequent use of salt at the table and use of non-animal fats for cooking), except for salt intake in Estonia.

CONCLUSIONS

Several misunderstood dietary concepts (myths) are still prevalent in the Baltic countries. Correct beliefs related to salt intake and types of fat were not consistent predictors of healthier food behaviours. In-depth qualitative investigations are needed to better describe and understand dietary beliefs and attitudes in the Baltic countries, and to identify barriers to the adoption of healthy food habits.

Role of endothelin B receptors in enhancing endothelium-dependent nitric oxide-mediated vascular relaxation during high salt diet

High salt diet is often associated with increases in blood pressure, and the state of activation of endothelium-dependent vascular relaxation pathways is critical under these conditions. Basal activation of endothelial endothelin B (ET(B)) receptors by endothelin has been suggested to stimulate the release of factors that promote vascular relaxation. However, whether ET(B) receptors play a role in enhancing endothelium-dependent vascular relaxation during high salt diet is unclear. In this study, we investigated whether chronic treatment with an ET(B) receptor antagonist is associated with impaired endothelium-dependent vascular relaxation and enhanced vascular reactivity particularly during high salt diet. Isometric contraction was measured in aortic strips isolated from male Sprague-Dawley rats on normal sodium (NS, 1%) and high sodium diet (HS, 8%) for 7 days and untreated or treated with the ET(B) receptor antagonist A-192621 (30 mg/kg per day) for 5 days. The mean arterial pressure was (in mm Hg) 122+/-3 in NS, 132+/-3 in HS, 144+/-2 in NS/ET(B) antagonist, and 171+/-12 in HS/ET(B) antagonist rats. In endothelium-intact strips, phenylephrine (Phe, 10(-5) mol/L) increased active stress to 7.6+/-1.0x10(3)N/m(2) in NS rats and 8.2+/-0.9x10(3)N/m(2) in HS rats. Phe (10(-5) mol/L) -induced stress was significantly greater in NS/ET(B) antagonist (11.3+/-0.9x10(3)N/m(2)) than NS and far greater in HS/ET(B) antagonist (14.1+/-0.1.2x10(3)N/m(2)) than HS rats. Also, Phe was more potent in NS/ET(B) antagonist and HS/ET(B) antagonist rats (ED(50)=0.3x10(-7) and 0.15x10(-7) mol/L) than in NS and HS rats (ED(50)=0.8x10(-7) and 0.7x10(-7) mol/L). Removal of the endothelium enhanced Phe-induced contraction significantly in NS and to a greater extent in HS, but not in NS/ET(B) antagonist or HS/ET(B) antagonist rats. In endothelium-intact strips, acetylcholine (ACh) caused relaxation of Phe contraction that was less in NS/ET(B) antagonist than NS and far less in HS/ET(B) antagonist than HS rats. Pretreatment of endothelium-intact strips with L-NAME (10(-4) mol/L), to inhibit nitric oxide (NO) synthase, or with methylene blue (10(-5) mol/L) or 1H-[1,2,4]oxadiazolo[4,3]-quinoxalin-1-one (ODQ, 10(-6) mol/L), to inhibit cGMP production in smooth muscle, inhibited ACh-induced relaxation and enhanced Phe-induced contraction significantly in NS and HS, slightly in NS/ET(B) antagonist, but not in HS/ET(B) antagonist rats. Measurement of basal and ACh-induced nitrite/nitrate production from aortic strips showed a significant reduction in NS/ET(B) antagonist compared with NS, and a greater reduction in HS/ET(B) antagonist compared with HS rats. Relaxation of Phe contraction with sodium nitroprusside was not significantly different among the different groups of rats. Thus, an endothelial ET(B) receptor-mediated pathway of vascular relaxation involving release of NO seems to be active under basal conditions and may protect against excessive vasoconstriction and increased blood pressure particularly during high salt diet.

Alpha-lactorphin lowers blood pressure measured by radiotelemetry in normotensive and spontaneously hypertensive rats

Cardiovascular effects of subcutaneous administration of synthetic alpha-lactorphin, a tetrapeptide (Tyr-Gly-Leu-Phe) originally derived from milk alpha-lactalbumin, were studied in conscious spontaneously hypertensive rats (SHR) and in normotensive Wistar Kyoto rats (WKY) with continuous radiotelemetric monitoring. Alpha-lactorphin dose-dependently lowered blood pressure (BP) without affecting heart rate in SHR and WKY. The lowest dose which reduced BP was 10 microg/kg, and the maximal reductions in systolic and diastolic BP (by 23+/-4 and 17+/-4 mm Hg, respectively) were observed at 100 microg/kg dose in SHR. No further reductions were obtained at a higher dose of 1 mg/kg. There were no significant differences in the BP responses to alpha-lactorphin between SHR and WKY. Naloxone (1 and 3 mg/kg s.c.), a specific opioid receptor antagonist, abolished the alpha-lactorphin-induced reduction in BP and reversed it into a pressor response, which provides evidence for an involvement of opioid receptors in the depressor action of the tetrapeptide.