Exploratory study on the relationship between urinary sodium/potassium ratio, salt intake, and the antihypertensive effect of esaxerenone: the ENaK Study.

Excessive salt intake is one of the causes of hypertension, and reducing salt intake is important for managing the risk of hypertension and subsequent cardiovascular events. Esaxerenone, a mineralocorticoid receptor blocker, has the potential to exert an antihypertensive effect in hypertensive patients with excessive salt intake, but evidence is still lacking, especially in clinical settings. We aimed to determine if baseline sodium/potassium ratio and baseline estimated 24-h urinary sodium excretion can predict the antihypertensive effect of esaxerenone in patients with essential hypertension inadequately controlled with an angiotensin receptor blocker (ARB) or a calcium channel blocker (CCB). This was an exploratory, open-label, interventional study with a 4-week observation period and a 12-week treatment period. Esaxerenone was orally administered once daily in accordance with the Japanese package insert. In total, 126 patients met the eligibility criteria and were enrolled (ARB subcohort, 67; CCB subcohort, 59); all were included in the full analysis set (FAS) and safety analysis. In the FAS, morning home systolic blood pressure (SBP)/diastolic blood pressure (DBP) significantly decreased from baseline to end of treatment (primary efficacy endpoint) (-11.9 ± 10.9/ - 6.4 ± 6.8 mmHg, both p < 0.001); a similar trend was observed in both subcohorts. Significant reductions were also shown in bedtime home and office SBP/DBP (all p < 0.001). Each BP change was consistent regardless of the urinary sodium/potassium ratio or estimated 24-h urinary sodium excretion at baseline. The urinary albumin-creatinine ratio (UACR) and N-terminal pro-brain natriuretic peptide (NT-proBNP) significantly decreased from baseline to Week 12 in the total population and both subcohorts. No new safety concerns were raised. Esaxerenone significantly decreased morning home, bedtime home, and office BP; UACR; and NT-proBNP in this patient population, regardless of concomitant ARB or CCB use. The antihypertensive effect of esaxerenone was independent of the urinary sodium/potassium ratio and estimated 24-h urinary sodium excretion at baseline.

Efficacy and Safety of Esaxerenone in Hypertensive Patients with Diabetes Mellitus Undergoing Treatment with Sodium-Glucose Cotransporter 2 Inhibitors (EAGLE-DH).

INTRODUCTION: The EAGLE-DH study assessed the efficacy and safety of esaxerenone in hypertensive patients with diabetes mellitus receiving sodium-glucose cotransporter 2 (SGLT2) inhibitors. METHODS: In this multicenter, open-label, prospective, interventional study, esaxerenone was started at 1.25 or 2.5 mg/day and could be gradually increased to 5 mg/day on the basis of blood pressure (BP) and serum potassium levels. Oral hypoglycemic or antihypertensive medications prior to obtaining consent was continued. Data were evaluated in the total population and creatinine-based estimated glomerular filtration rate (eGFR) subcohorts (eGFR ≥ 60 mL/min/1.73 m2 [G1-G2 subcohort] and 30 to < 60 mL/min/1.73 m2 [G3 subcohort]). RESULTS: In total, 93 patients were evaluated (G1-G2, n = 49; G3, n = 44). Morning home systolic/diastolic BP values (SBP/DBP) were significantly reduced from baseline to week 12 (- 11.8 ± 10.8/- 5.1 ± 6.3 mmHg, both P < 0.001) and week 24 (- 12.9 ± 10.5/- 5.7 ± 6.3 mmHg, both P < 0.001). Similar results were observed in both eGFR subcohorts. The urinary albumin-to-creatinine ratio significantly decreased from baseline to week 24 in the total population (geometric percentage change, - 49.1%, P < 0.001) and in both eGFR subcohorts. The incidences of treatment-emergent adverse events (TEAEs) and drug-related TEAEs were 45.2% and 12.9%, respectively; most were mild or moderate. Serum potassium levels increased over the first 2 weeks of esaxerenone treatment, gradually decreased by week 12, and remained constant to week 24. One patient in the G1-G2 subcohort had serum potassium levels ≥ 5.5 mEq/L. No patients had serum potassium ≥ 6.0 mEq/L. CONCLUSION: Esaxerenone effectively lowered BP, was safe, and showed renoprotective effects in hypertensive patients with diabetes mellitus receiving treatment with SGLT2 inhibitors. Esaxerenone and SGLT2 inhibitors did not interfere with either drug's efficacy and may reduce the frequency of serum potassium elevations, suggesting they are a compatible combination. CLINICAL TRIAL REGISTRATION: jRCTs031200273.

Associated Factors and Comorbidities of Airflow Limitation in Subjects Undergoing Comprehensive Health Examination in Japan - Survey of Chronic Obstructive Pulmonary Disease Patients Epidemiology in Japan (SCOPE- J).

Purpose: To identify associated factors of having at least one of the airflow limitation, chronic cough/phlegm, and currently treated respiratory diseases in health examinees, and to describe the characteristics of each subgroup classified by comorbidities. Subjects and Methods: This was an observational cross-sectional survey carried out in multiple regions of Japan. Subjects aged 40 years older, undergoing comprehensive health examination, were recruited. Airflow limitation was defined as having forced expiratory volume in 1 s/forced vital capacity lower than 70%. Associated factors of having at least one of the airflow limitation, chronic cough/phlegm, and currently treated respiratory diseases were examined by logistic regression analysis. Subgroup classification by comorbidity patterns was conducted by hierarchical cluster analysis. Results: In a total of 22,293 subjects, 1520 (6.8%) had at least one of the airflow limitation, chronic cough/phlegm, and currently treated respiratory diseases. With this objective variable, the following explanatory variables were significantly associated: older age, higher total score in the chronic obstructive pulmonary disease assessment test (CAT) and coexistence of lung cancer (common in ever-smokers and never-smokers), higher pack-years, lower body mass index, higher C-reactive protein, without coexistence of diabetes mellitus (specific in ever-smokers), male sex, coexistence of anxiety, and sleep disorder (specific in never-smokers). Among the 1520 subjects, 1512 subjects with smoking history data were classified by comorbidity patterns into subgroups of "no comorbidities," "mixed comorbidities," "inflammatory comorbidities," "overweight," "underweight," and "chronic kidney disease." "Inflammatory comorbidities" were specific in ever-smokers, and "underweight" was specific in never-smokers. Conclusion: Several factors were identified as associated factors of having at least one of airflow limitation, chronic cough/phlegm, and currently treated respiratory diseases and they were different between ever-smokers and never-smokers. Different comorbidity patterns were observed by smoking history. These findings could provide information to assist the management of subjects with COPD or at risk for COPD in the general population.

Chronic Cough and Phlegm in Subjects Undergoing Comprehensive Health Examination in Japan - Survey of Chronic Obstructive Pulmonary Disease Patients Epidemiology in Japan (SCOPE-J).

Purpose: The purpose of this study was to estimate the prevalence of subjects with chronic cough and phlegm and describe their characteristics including the presence or absence of airflow limitation among the general population in Japan. Subjects and Methods: This was an observational cross-sectional survey targeting multiple regions of Japan. Subjects aged 40 years or above who were undergoing comprehensive health examination were recruited. The existence of chronic cough and phlegm, airflow limitation, and treatment for respiratory diseases were examined. Chronic cough and phlegm were defined as having both symptoms for at least 3 months of the year and for at least 2 consecutive years, or as receiving any treatment for chronic bronchitis at the time of recruitment. Airflow limitation was defined as forced expiratory volume in 1 s/forced vital capacity (FEV1/FVC) less than 0.7. Results: In a total of 22,293 subjects, 380 subjects (1.7%) had chronic cough and phlegm. Among these 380 subjects, 21.8% received treatment for a respiratory disease, and 11.6% had airflow limitation. Compared to subjects without both chronic cough and phlegm but with airflow limitation, subjects with chronic cough and phlegm without airflow limitation were younger, more likely to be current smokers (39.6%), and had higher total scores on a chronic obstructive pulmonary disease (COPD) assessment test (CAT). Scores of CAT questions 1-4 (cough, phlegm, chest tightness, breathlessness, respectively) were higher in subjects with chronic cough and phlegm regardless of airflow limitation. Conclusion: This study demonstrated that subjects identified to have chronic cough and phlegm in comprehensive health examination settings were symptomatic, while most of them did not receive any treatment for respiratory diseases and did not have airflow limitation. Screening subjects for chronic cough and phlegm in a comprehensive health examination followed by a detailed examination of screened subjects could be an effective approach for better management of chronic cough and phlegm. Smoking cessation should be included in the management, in consideration that around 40% of subjects with chronic cough and phlegm were current smokers.

Short-Term Efficacy (at 12 Weeks) and Long-Term Safety (up to 52 Weeks) of Omega-3 Free Fatty Acids (AZD0585) for the Treatment of Japanese Patients With Dyslipidemia　- A Randomized, Double-Blind, Placebo-Controlled, Phase III Study.

BACKGROUND: This study is the first to evaluate the short-term efficacy and long-term safety of AZD0585, a mixture of omega-3 free fatty acids, in Japanese patients with dyslipidemia.Methods and Results:In this randomized double-blind placebo-controlled Phase III study, 383 patients were randomized to 2 g AZD0585, 4 g AZD0585, or placebo once daily for 52 weeks. Eligible patients had low-density lipoprotein cholesterol (LDL-C) levels controlled regardless of statin use, and triglyceride levels between 150 and 499 mg/dL. The least-squares (LS) mean percentage changes in triglyceride concentrations from baseline to the 12-week endpoint (mean of measurements at Weeks 10 and 12) in the 2 and 4 g AZD0585 and placebo groups were -15.57%, -21.75%, and 11.15% respectively (P<0.0001 for both AZD0585 doses vs. placebo). No clinically significant changes from baseline to the 12-week endpoint in total cholesterol, LDL-C, and LDL-C/apolipoprotein (Apo) B were found with AZD0585. High-density lipoprotein cholesterol (HDL-C) was slightly increased and very low-density lipoprotein cholesterol, non-HDL-C, ApoC-II, and ApoC-III were decreased with AZD0585 compared with placebo at the 12-week endpoint. Lipid profiles up to Week 52 were consistent with those up to the 12-week endpoint. No clinically important safety concerns were raised. CONCLUSIONS: AZD0585 significantly decreased serum triglyceride levels compared with placebo at the 12-week endpoint and was generally safe and well tolerated in Japanese patients with dyslipidemia.

Early diagnosis of type 2 diabetes based on multiple biomarkers and non-invasive indices.

We previously reported that type 2 diabetes risk, early impaired glucose tolerance and insulin resistance can be predicted by measuring the fasting levels of certain biomarkers. Here we validated these findings in randomly recruited healthy volunteers (n = 101) based on biomarker expression as well as various non-invasive indices. Weight, body mass index, waist circumference and visceral fat differed between individuals with impaired fasting glucose and/or impaired glucose tolerance, and normal subjects. Fasting plasma levels of glycated hemoglobin, leptin, pro-insulin and retinol binding protein 4 differed between impaired fasting glucose/impaired glucose tolerance and normal subjects group and between newly detected diabetes and normal subjects group. Insulin resistance was correlated with fasting levels of insulin and leptin/adiponectin (r = 0.913); of insulin, retinol binding protein 4 and leptin/adiponectin (r = 0.903); and of insulin, glycated albumin, and leptin/adiponectin (r = 0.913). Type 2 diabetes risk, early impaired glucose tolerance and insulin resistance were predicted with >98% specificity and sensitivity by comparing fasting glucose levels to the estimated Matsuda Index based on fasting levels of insulin, adiponectin and leptin with or without oxidative lineolate metabolites. Non-invasive indices are slightly correlated with glucose tolerance and insulin resistance but do not increase the accuracy of predicting type 2 diabetes risk.

The impact of theaflavins on systemic-and microcirculation alterations: The murine and randomized feasibility trials.

Theaflavins are polyphenols found in black tea; their physiological activities were not well investigated. The present study in rats evaluated the influence of theaflavins on circulation. In addition, an intervention pilot study examined the influence of a theaflavin drink on postprandial hemodynamic change. In an animal study, a single oral dose of theaflavin rich fraction (TF, 10mg/kg) caused transient increase in mean blood pressure (MBP) and heart rate (HR). TF also elevated cremastric blood flow significantly, and the magnitude of this effect was in this order: theaflavin 3'-O-gallate (TF2B) >>theaflavin-3-O-gallate (TF2A) >>theaflavin (TF1)=theaflavin-3, 3'-di-O-gallate (TF3). In addition, these hemodynamic alterations in mammals totally disappeared when pretreated with carvedilol as an adrenaline blocker. We also treated 10-mg/kg/day TF to the rats for 2 weeks. At the end of the ingestion period, MBP was reduced significantly, and aortic eNOS level was elevated by the repeated ingestion of TF compared with distilled water. In the intervention trial, blood pressure of the volunteers was increased significantly 2 and 4h after ingestion of the TF drink (45mg/drink) compared with before treatment. A significant difference was observed in FMD between the placebo and theaflavin groups 4h after ingestion. These results suggested that theaflavin has potent activity to alter hemodynamics in both murine and healthy subjects. Further studies is needed to elucidate the details; however, the results of animal study suggested that the possible involvement of sympathetic nervous system in the hemodynamic changes caused by TF.

Effects of Febuxostat on Oxidative Stress.

PURPOSE: We previously examined factors that affect the measured derivatives of reactive oxygen metabolites (d-ROMs), an indicator of reactive oxygen species production, and biological antioxidant potential (BAP), an indicator of antioxidant capacity, in typical health checkup examinees and reported the usefulness of measuring both indicators simultaneously. In addition, a positive correlation reportedly exists between d-ROMs and the visceral fat area measured by using computed tomography. A recent study of the relationship between uric acid levels and various obesity-related factors found that visceral fat was the factor most strongly related to uric acid levels. Uric acid is itself a potent endogenous antioxidant, but because reactive oxygen species are produced during uric acid generation, it is suggested that uric acid may have opposing effects. The objective of this study was to analyze the effect of febuxostat, a novel xanthine oxidase inhibitor, on oxidative stress. METHODS: Study subjects were 43 hyperuricemia outpatients receiving care in the internal medicine department of our institution. The subjects were divided into a new administration group (29 patients) and a switched administration group (14 patients); the latter were allopurinol-treated patients with hyperuricemia who were switched to febuxostat. In addition to measuring the patients' uric acid and creatinine levels and estimated glomerular filtration rate before and after treatment, their d-ROMs and BAP as well as the BAP/d-ROMs ratio were also measured. FINDINGS: Both groups exhibited significant decreases in uric acid levels, as well as significant decreases in d-ROMs and BAP. No significant changes were observed in the BAP/dROMs ratio or renal function, including creatinine levels and estimated glomerular filtration rate. IMPLICATIONS: Febuxostat could significantly reduce d-ROMs. However, BAP levels were also significantly reduced concurrently. No changes were observed in the BAP/d-ROMs ratios. This regulatory mechanism is believed to have counteracted changes in the in vivo oxidative stress balance caused by febuxostat administration.

Reduction of visceral fat correlates with the decrease in the number of obesity-related cardiovascular risk factors in Japanese with Abdominal Obesity (VACATION-J Study).

AIM: Visceral fat accumulation is associated with obesity-related cardiovascular risk factor accumulation and atherosclerosis. The present study investigated whether one-year reduction of the visceral fat area (VFA) correlates with a decrease in the number of such factors in Japanese with or without visceral fat accumulation. METHODS: The study subjects comprised 5,347 Japanese, who underwent health check-ups in 2007 and 2008, including measurements of VFA and subcutaneous fat area (SFA) by computed tomography at 9 centers in Japan. Subjects with one or more such factor(s) were categorized into tertiles based on the one-year change in VFA. We investigated the multivariate age, sex, and one-year change in SFA-adjusted odds ratios (ORs) and 95% confidence intervals (CI) for reductions in the number of risk factors in each of the three categories based on the one-year change in VFA, in subjects with one or more such factors (n= 3,648). RESULTS: In the entire group (n=3,648), the OR and 95%CI for reductions in the number of risk factors in the first tertile were 0.804 (0.673-0.962, p=0.0172), compared with the second tertile set at 1.0. Subjects with VFA <100cm(2) showed no reduction in the number of risk factors. In subjects with VFA≥100 cm(2), OR in the first tertile was 0.788 (0.639-0.972, p=0.0257) relative to the second tertile set at 1.0. CONCLUSIONS: In subjects with multiple cardiovascular risk factors, visceral fat reduction correlated with a decrease in the number of such factors in subjects with VFA≥100cm(2), but not in those with VFA<100cm(2).

Absolute value of visceral fat area measured on computed tomography scans and obesity-related cardiovascular risk factors in large-scale Japanese general population (the VACATION-J study).

BACKGROUND: The management of cardiovascular risk factors is important for prevention of atherosclerotic cardiovascular diseases (ACVD). Visceral fat accumulation plays an important role in the clustering of cardiovascular risk factors, leading to ACVD. The present study investigated the gender- and age-specific relationship between obesity-related cardiovascular risk factor accumulation and computed tomography (CT)-measured fat distribution in a large-scale Japanese general population. METHODS AND RESULTS: Fat distribution was measured on CT scans in 12,443 subjects (males/females = 10,080/2,363), who underwent medical health check-up at 9 centers in Japan. The investigated obesity-related cardiovascular risk factors were hyperglycemia, dyslipidemia, and elevated blood pressure. Visceral fat area (VFA) for all males and old females showed almost symmetric distribution, while that of young females showed skewed distribution with a marked left shift. Only a small proportion of young females had large visceral fat and cardiovascular risk accumulation. The mean number of risk factors exceeded 1.0 at around 100 cm(2) for VFA in all groups, irrespective of gender, age (cut-off age 55), and BMI (cut-off BMI 25 kg/m(2)). CONCLUSIONS: In this large-scale Japan-wide general population study, an absolute VFA value of about 100 cm(2) equated with obesity-related cardiovascular risk factor accumulation, irrespective of gender, age, and BMI.

Roles of central renin-angiotensin system and afferent renal nerve in the control of systemic hemodynamics in rats.

Afferent renal nerves (ARNs) convey signals generated by physiological changes in the kidney to the central nervous system. The aim of this study was to determine whether ARNs contribute to cardiovascular regulation through central renin-angiotensin system (RAS)-dependent pathways. Blood pressure and renal sympathetic nerve activity (RSNA) were monitored during elevations in pelvic pressure in anesthetized Wistar-Kyoto Izm (WKY) rats and spontaneously hypertensive Izm rats (SHRs). In both groups of rats, blood pressure and RSNA were significantly increased in response to elevations in renal pelvic pressure in a pressure-dependent fashion, which were prevented by renal denervation. Injection of an angiotensin II type I receptor blocker (CV-11974, 10 µg) into the intracerebroventricular region significantly suppressed the vasopressor and sympathoexcitatory responses to the increases in pelvic pressure in both WKY rats and SHRs, although these inhibitory effects of CV-11974 in SHRs appeared to be weaker than in WKY rats. These results indicate that signals transmitted by ARNs have an important role in the control of systemic hemodynamics through regulating central RAS-mediated changes in sympathetic nerve activity.

Significance of measuring oxidative stress in lifestyle-related diseases from the viewpoint of correlation between d-ROMs and BAP in Japanese subjects.

In recent years, oxidative stress has been postulated to be an important factor in the pathogenesis and development of lifestyle-related diseases. In this study, we investigated the association between the derivatives of reactive oxygen metabolites (d-ROMs), as an index of products of reactive oxygen species (ROS), and biological antioxidant potential (BAP), as an index of antioxidant potential. We also investigated the associations between d-ROMs or BAP and the risk factors for lifestyle-related diseases or metabolic syndrome-associated factors to evaluate their usefulness in preventive medicine. There were 442 subjects who underwent health checkup examination in our facilities. In addition to standard medical checkup items, we analyzed d-ROMs, BAP, brachial-ankle pulse wave velocity, high-sensitivity C-reactive protein level and visceral fat area (VFA) visualized on a computed tomography scan. The mean d-ROM value in females was significantly higher than that in males. There was a positive correlation between the d-ROM and VFA levels. On correlation analysis, there was a negative correlation between the d-ROM and creatinine levels. As factors that influence d-ROMs, the level of VFA was selected, suggesting the significance of oxidative stress measurement with d-ROMs. In addition, there was a positive correlation between d-ROMs and BAP values. Further research is required to resolve whether increased production of ROS or the antioxidant potential that can compensate for such an increase of ROS is more important in vivo.

Synergistic effect of mechanical stretch and angiotensin II on superoxide production via NADPH oxidase in vascular smooth muscle cells.

OBJECTIVE: Mechanical forces and angiotensin II influence the structure and function of vascular cells, and play an important role in reactive oxygen species production. In this study, we examined the effects of mechanical stretch and angiotensin II on the expression of p22-phox and Nox-1, essential membrane components of NADPH oxidase, and superoxide production in rat vascular smooth muscle cells (VSMCs). METHODS AND RESULTS: Neither a stretch force nor angiotensin II alone altered p22-phox and Nox-1 expression in VSMCs. Combined stimulation markedly increased p22-phox and Nox-1 mRNA, however, which was associated with increased NADPH oxidase activity, superoxide production and total 8-iso-prostaglandin F2alpha concentration. The increases in p22-phox mRNA levels induced by a stretch force in combination with angiotensin II were prevented by treatment with an angiotensin type I (AT1) receptor antagonist, RNH-6270 (100 nmol/l). Protein expression of the AT1 receptor was upregulated by a stretch force. CONCLUSIONS: These data indicate that mechanical stretch and angiotensin II synergistically increase NADPH oxidase expression in VSMCs, and suggest that part of this mechanism is mediated through an upregulation of the AT1 receptor induced by mechanical stretch. The combined effects of mechanical strain and angiotensin II might promote vascular damage through the production of superoxide in a hypertensive state.

Role of angiotensin II and reactive oxygen species in cyclosporine A-dependent hypertension.

Treatment with cyclosporine A (CysA), a potent immunosuppressive agent, is associated with systemic and renal vasoconstriction, leading to hypertension. The present study was conducted to elucidate the contribution of angiotensin II (Ang II) to CysA-induced hypertension and reactive oxygen species (ROS) generation. CysA (30 mg/kg per day SC), given for 3 weeks in rats, increased systolic blood pressure (SBP) from 119+/-2 to 145+/-3 mm Hg (n=7). Plasma and kidney Ang II levels were significantly higher in CysA-treated rats (136+/-10 fmol/mL and 516+/-70 fmol/g) than in vehicle-treated (1 mL olive oil) rats (76+/-10 fmol/mL and 222+/-21 fmol/g, n=7). CysA treatment increased AT1 receptor protein expression in the aorta (by 251+/-35%), whereas it was reduced in the kidney (by -32+/-4%). Superoxide anion production in aortic segments and kidney thiobarbituric acid-reactive substance (TBARS) contents were higher in CysA-treated rats (26+/-2 counts/min per milligram and 37+/-3 nmol/g) than in vehicle-treated rats (17+/-1 counts/min per milligram and 24+/-3 nmol/g). Concurrent administration of an AT1 receptor antagonist, valsartan (30 mg/kg per day, in drinking water), to CysA-treated rats (n=7) significantly decreased SBP (113+/-4 mm Hg) and prevented increases in vascular superoxide (16+/-2 counts/min per milligram) and kidney TBARS contents (21+/-3 nmol/g). Similarly, treatment with a superoxide dismutase mimetic, 4-hydroxy-2,2,6,6,-tetramethylpiperidine-N-oxyl (Tempol; 3 mmol/L in drinking water, n=7), prevented CysA-induced increases in SBP (115+/-3 mm Hg), vascular superoxide (16+/-1 counts/min per milligram), and kidney TBARS contents (19+/-2 nmol/g). These data suggest that ROS generation induced by augmented Ang II levels contributes to the development of CysA-induced hypertension.

Effects of angiotensin II on the renal interstitial concentrations of NO2/NO3 and cyclic GMP in anesthetized rats.

The present study was conducted to determine whether exogenous angiotensin II (Ang II) may increase the renal interstitial fluid concentrations of NO2/NO3 (NOx) and cyclic guanosine monophosphate (cGMP) concomitantly and which Ang II receptor subtypes may induce these changes in anesthetized rats, using a microdialysis method. Ang II (50 ng/kg per min, i.v.) significantly increased mean blood pressure (MBP), extraction rates of renal interstitial NOx from 23.9+/-1.0 to 31.2+/-1.9 pmol/min, and cGMP from 4.1+/-0.3 to 6.4+/-0.5 fmol/min, and decreased renal blood flow (RBF). The AT1-receptor antagonist CV11974 alone significantly increased RBF, but did not alter MBP, renal interstitial concentrations of NOx and cGMP. A superimposition of Ang II on CV11974 did not affect MBP and RBF, but significantly increased renal interstitial concentrations of NOx and cGMP. The AT2-receptor antagonist PD123319 alone did not change any of the parameters. However, superimposition of Ang II on PD123319 increased MBP and decreased RBF without any effects on renal interstitial concentrations of NOx and cGMP. These results suggest that Ang II stimulates NO production via the AT2-receptor in the kidney.

Blood flow-dependent changes in renal interstitial guanosine 3',5'-cyclic monophosphate in rabbits.

We examined responses of renal interstitial guanosine 3',5'-cyclic monophosphate (cGMP) to changes in renal perfusion pressure (RPP) within and below the range of renal blood flow (RBF) autoregulation. A microdialysis method was used to monitor renal cortical and medullary interstitial cGMP levels in anesthetized rabbits. RPP was reduced in two steps: from ambient pressure (89 +/- 3 mmHg) to 70 +/- 2 mmHg (step 1) and then to 48 +/- 3 mmHg (step 2). RBF was maintained in step 1 but was significantly decreased in step 2 from 2.94 +/- 0.23 to 1.47 +/- 0.08 ml x min(-1) x g(-1). Basal interstitial concentrations of cGMP were significantly lower in the cortex than in the medulla (12.1 +/- 1.4 and 19.9 +/- 0.4 nmol/l, respectively). Cortical and medullary cGMP did not change in step 1 but were significantly decreased in step 2, with significantly less reduction in cGMP concentrations in the medulla than in the cortex (-25 +/- 3 and -44 +/- 3%, respectively). Over this pressure range, changes in cortical and medullary cGMP were highly correlated with changes in RBF (r = 0.94, P < 0.005 for cortex; r = 0.82, P < 0.01 for medulla). Renal interstitial nitrate/nitrite was not changed in step 1 but was significantly decreased in step 2 (-38 +/- 2% in cortex and -20 +/- 2% in medulla). Nitric oxide synthase inhibition with N(G)-nitro-L-arginine methyl ester (L-NAME, 30 mg/kg bolus, 50 mg x kg(-1) x h(-1) i.v. infusion) significantly decreased RBF (by -46 +/- 4%) and interstitial concentrations of cGMP (-27 +/- 4% in cortex and -22 +/- 4% in medulla, respectively). During L-NAME treatment, renal interstitial concentrations of cGMP in the cortex and medulla were similarly not altered in step 1. However, L-NAME significantly attenuated cGMP responses to a reduction in RPP in step 2. These results indicate that acute changes in RBF result in alterations in nitric oxide-dependent renal interstitial cGMP levels, with differential effects in the medulla compared with the cortex.

Systemic and Regional Hemodynamic Responses to Tempol in Angiotensin II-Infused Hypertensive Rats.

-Recent studies have indicated that angiotensin II (Ang II) can stimulate oxidative stress. The present study was conducted to assess the contribution of oxygen radicals to hypertension and regional circulation during Ang II-induced hypertension. With radioactive microspheres, the responses of systemic and regional hemodynamics to the membrane-permeable, metal-independent superoxide dismutase mimetic 4-hydroxy-2,2,6,6-tetramethyl piperidinoxyl (tempol) were assessed in conscious Ang II-infused hypertensive rats. Ang II-infused rats (80 ng/min SC for 12 days: n=25) showed higher mean arterial pressure (MAP: 161+/-4 mm Hg) and total peripheral resistance (TPR: 1.59+/-0.08 mm Hg. min(-1). mL(-1)) than vehicle-infused normotensive rats (116+/-3 mm Hg and 0.95+/-0.04 mm Hg. min(-1). mL(-1), respectively; n=23). The blood flow rates in the brain, spleen, large intestine, and skin were significantly reduced in Ang II-infused rats compared with vehicle-infused rats, whereas rates in the lung, heart, liver, kidney, stomach, small intestine, mesenterium, skeletal muscle, and testis were similar. Vascular resistance was significantly increased in every organ studied except the lung, in which the resistance was similar. Tempol (216 µmol/kg IV) significantly reduced MAP by 30+/-4% from 158+/-7 to 114+/-5 mm Hg and TPR by 35+/-6% from 1.57+/-0.17 to 0.95+/-0.04 mm Hg. min(-1). g(-1) in Ang II-infused rats (n=9) but had no effect on these parameters in vehicle-infused rats (n=8). In Ang II-infused rats, tempol did not affect regional blood flow but significantly decreased vascular resistance in the brain (29+/-6%), heart (31+/-6%), liver (37+/-7%), kidney (30+/-7%), small intestine (38+/-6%), and large intestine (47+/-7%). Ang II-infused hypertensive rats showed doubled vascular superoxide production (assessed with lucigenin chemiluminescence), which was normalized by treatment with tempol (3 mmol/L, n=7). Further studies showed that the NO synthase inhibitor, N:(omega)-nitro-L-arginine methyl ester (11 µmol. kg(-1). min(-1) IV, n=11) markedly attenuated the systemic and regional hemodynamic responses of tempol in Ang II-infused rats. These results suggest that in this model of hypertension, oxidative stress may have contributed to the alterations in systemic blood pressure and regional vascular resistance through inactivation of NO.