Elevated plasma catecholamines in hypertensives with primary glomerular diseases

Bridging the gap-Rethinking the role of the adrenal gland in chronic kidney disease from the feline perspective

Chronic kidney disease (CKD) is the most common metabolic disease in domestic cats. Unlike humans and dogs, CKD in cats seems to have a highly complex and multifactorial etiology. Despite great effort being poured into research trying to elucidate possible pathways for the pathogenesis of CKD, there is still a lack of understanding regarding its initiating and progression factors. There is also a lack of therapeutic options for these patients, with most treatment plans relying on a low-phosphate diet, dietary protein modification and medical management of complications (e.g. hypertension) as they arise. In this review, we propose the hypothalamic-pituitary-adrenal (HPA) axis plays a central role in the development, pathophysiology and progression of feline chronic kidney disease. The adrenal glands and the hormones they secrete, in particular, may act as lynchpins in chronic kidney disease, mediating virtually every aspect of the disease: from the establishment of fibrosis and kidney damage to the development of hypertension and a pro-inflammatory status. By compiling the available research regarding the influence of adrenal hormones and the HPA axis, we hope to highlight possible future areas of scientific interest regarding feline CKD as well as possible aspects in which the cat may act as a model for research in human medicine.

The impact of anticoagulation therapy on kidney function in patients with atrial fibrillation and chronic kidney disease

INTRODUCTION

Atrial fibrillation (AF) and chronic kidney disease (CKD) are closely related. These diseases share common risk factors and are associated with increased risk of thromboembolic events. Choosing the appropriate oral anticoagulant therapy (OAC) in patients with AF and CKD is challenging. Deterioration of renal function is common in patients with AF treated with OACs, although not all OACs affect the kidneys equally.

AREAS COVERED

In this review, we aim to summarize the current knowledge of the prevention of thromboembolic events in patients with AF and CKD, focusing on the impact of specific OAC agents on renal function.

EXPERT OPINION

Consideration of OAC use is mandatory in patients with AF and CKD who are at increased risk of stroke or systemic embolism. Available evidence suggests that the use of non-vitamin K antagonist oral anticoagulants (NOACs) is associated with slower deterioration of renal function in comparison to Vitamin K antagonists (VKAs). Hence, a NOAC should be used in preference to VKAs in all NOAC-eligible patients with AF and CKD. Regarding patients with end-stage renal dysfunction and those on dialysis or renal replacement therapy, the use of NOAC should be considered in line with locally relevant formal recommendations.

Exercise modulates sympathetic and vascular function in chronic kidney disease

BACKGROUNDChronic kidney disease (CKD) is characterized by chronic overactivation of the sympathetic nervous system (SNS), which increases the risk of cardiovascular (CV) disease and mortality. SNS overactivity increases CV risk by multiple mechanisms, including vascular stiffness. We tested the hypothesis that aerobic exercise training would reduce resting SNS activity and vascular stiffness in patients with CKD.METHODSIn this randomized controlled trial, sedentary older adults with CKD underwent 12 weeks of exercise (cycling, n = 32) or stretching (an active control group, n = 26). Exercise and stretching interventions were performed 20-45 minutes/session at 3 days/week and were matched for duration. Primary endpoints include resting muscle sympathetic nerve activity (MSNA) via microneurography, arterial stiffness by central pulse wave velocity (PWV), and aortic wave reflection by augmentation index (AIx).RESULTSThere was a significant group × time interaction in MSNA and AIx with no change in the exercise group but with an increase in the stretching group after 12 weeks. The magnitude of change in MSNA was inversely associated with baseline MSNA in the exercise group. There was no change in PWV in either group over the study period.CONCLUSIONOur data demonstrate that 12 weeks of cycling exercise has beneficial neurovascular effects in patients with CKD. Specifically, exercise training safely and effectively ameliorated the increase in MSNA and AIx observed over time in the control group. This sympathoinhibitory effect of exercise training showed greater magnitude in patients with CKD with higher resting MSNA.TRIAL REGISTRATIONClinicalTrials.gov, NCT02947750.FUNDINGNIH R01HL135183; NIH R61AT10457; NIH NCATS KL2TR002381; and NIH T32 DK00756; NIH F32HL147547; and VA Merit I01CX001065.

Sympathetic activation and heart rate thresholds for cardiovascular risk in chronic kidney disease

AIM

The current study was designed at assessing whether the sympathetic cardiovascular drive (SNS) is differently activated in chronic kidney disease (CKD) patients displaying less or more elevated resting heart rate (HR) values. It was also designed at determining at which HR cutoff value the SNS displays a greater activation.

METHODS

In 95 CKD middle-age patients we evaluated muscle sympathetic nerve activity (MSNA, microneurography) and venous plasma norepinephrine (HPLC assay), subdividing the patients in different groups according to their resting clinic and 24-h HR.

RESULTS

In CKD progressively greater values of clinic or 24-h HR were associated with a progressive increase in both MSNA and norepinephrine. HR cutoff values indicated by large-scale clinical trials for determining cardiorenal risk, that is more than 80 bpm, were associated with MSNA values significantly greater than the ones detected in patients with lower HR, this being the case also for norepinephrine. Both MSNA and norepinephrine were significantly related to clinic ( r  = 0.47, P  < 0.0001 and r  = 0.26, P  < 0.0001, respectively) and 24-h ( r  = 0.42, P  < 0.0001 and r  = 0.27, P  < 0.0001, respectively) HR. MSNA, norepinephrine, but not HR, were significantly and inversely related to estimated glomerular filtration rate (eGFR) values ( r  = -0.47, r  = -0.23, P  < 0.0001 and P  < 0.02, respectively).

CONCLUSION

In CKD both clinic and 24-h HR values greater than 80 bpm are associated with an enhanced sympathetic activation, which parallelles for magnitude the HR elevations. The sensitivity of HR as sympathetic marker is limited; however, no significant relationship being detected between HR and eGFR or left ventricular mass index.

Autonomic Cardiovascular Alterations in Chronic Kidney Disease: Effects of Dialysis, Kidney Transplantation, and Renal Denervation

PURPOSE OF REVIEW

To review the results of studies of the effects of dialysis and kidney transplantation on the autonomic nervous system alterations that occur in chronic kidney disease.

RECENT FINDINGS

Vagal control of the heart mediated by arterial baroreceptors is altered early in the course of the renal disease. Sympathetic activation occurs, with increases in resting heart rate, venous plasma norepinephrine levels, muscle sympathetic nerve traffic, and other indirect indices of adrenergic drive. The magnitude of the changes reflects the clinical severity of the kidney disease. Both the sympathetic and parasympathetic alterations have a reflex origin, depending on the impairment in baroreflex and cardiopulmonary reflex control of the cardiovascular system. These alterations are partially reversed during acute hemodialysis, but the responses are variable depending on the specific type of dialytic treatment that is employed. Renal transplantation improves reflex cardiovascular control, resulting in sympathoinhibition following renal transplantation if the native kidneys are removed. Sympathoinhibitory effects have been also reported in renal failure patients after bilateral renal denervation. Assessment of autonomic nervous system responses to dialysis and renal transplantation provides information of clinical interest, given the evidence that autonomic alterations are involved in the development and progression of cardiovascular complications, as well as in the prognosis of chronic kidney disease.

Limited reliability of heart rate as a sympathetic marker in chronic kidney disease

BACKGROUND

Chronic kidney disease (CKD) is characterized by a pronounced sympathetic overactivity as documented by the marked increase in muscle sympathetic nerve traffic (MSNA) and in plasma norepinephrine reported in this condition. Whether and to what extent in CKD heart rate (HR) reflects the adrenergic overdrive remains undefined. It is also undefined the relative validity of the different adrenergic markers in reflecting renal dysfunction.

MATERIALS AND METHODS

In 82 CKD patients, aged 58.4 ± 1.1 years (mean ± SEM), we measured resting clinic blood pressure, HR (EKG), venous NE (HPLC) and MSNA (microneurography). The same measurements were made in 24 age-matched healthy controls.

RESULTS

HR was significantly greater in CKD than in controls (74.0 ± 1.1 versus 68.2 ± 1.8 bpm, P < 0.02) and significantly directly related to the elevated plasma norepinephrine and MSNA values (r = 0.22 and 0.39, P < 0.05 and <0.0003, respectively). Both MSNA and plasma norepinephrine were significantly and inversely related to the estimated glomerular filtration rate. The correlation did not achieve statistical significance for HR. Similar results were obtained examining the relationships with left ventricular mass index.

CONCLUSION

Our data show that in CKD not only peripheral but also cardiac sympathetic drive is markedly enhanced and HR can be regarded as a marker of the adrenergic overdrive characterizing this condition. The reliability of HR as sympathetic marker appears to be limited, however, this variable being unable to closely reflect, at variance from MSNA and plasma norepinephrine, the interindividual differences in renal dysfunction and the accompanying structural cardiovascular alterations.

Implications of Kidney Disease in the Cardiac Patient

Cardiovascular and renal diseases share common pathophysiological grounds, risk factors, and therapies. The 2 entities are closely interlinked and often coexist. The prevalence of kidney disease among cardiac patients is increasing. Patients have an atypical clinical presentation and variable disease manifestation versus the general population. Renal impairment limits therapeutic options and worsens prognosis. Meticulous treatment and close monitoring are required to ensure safety and avoid deterioration of kidney and heart functions. This review highlights recent advances in the diagnosis and treatment of cardiac pathologies, including coronary artery disease, arrhythmia, and heart failure, in patients with decreased renal function.

Vascular α1-adrenergic sensitivity is enhanced in chronic kidney disease

Chronic kidney disease (CKD) is often complicated by difficult-to-control hypertension, in part due to chronic overactivation of the sympathetic nervous system (SNS). CKD patients also exhibit a greater increase in arterial blood pressure for a given increase in sympathetic nerve activation, suggesting an augmented vasoconstrictive response to SNS activation (i.e., neurovascular transduction). One potential mechanism of increased sympathetic neurovascular transduction is heightened sensitivity of the vascular α₁-adrenergic receptors (α₁ARs), the major effectors of vasoconstriction in response to norepinephrine release at the sympathetic nerve terminals. Therefore, we hypothesized that patients with CKD have increased vascular α₁AR sensitivity. We studied 32 patients with CKD stages III and IV (age 59.9 ± 1.3 yr) and 19 age-matched controls (CON, age 63.2 ± 1.6 yr). Using a linear variable differential transformer (LVDT), we measured change in venoconstriction in response to exponentially increasing doses of the selective α₁AR agonist phenylephrine (PE) administered sequentially into a dorsal hand vein. Individual semilogarithmic PE dose-response curves were constructed for each participant to determine the PE dose at which 50% of maximum venoconstriction occurred (ED₅₀), reflecting α₁AR sensitivity. In support of our hypothesis, CKD patients had a lower PE ED₅₀ than CON (CKD = 2.23 ± 0.11 vs. CON = 2.63 ± 0.20, P = 0.023), demonstrating increased vascular α₁AR sensitivity. Additionally, CKD patients had a greater venoconstrictive capacity to PE than CON (P = 0.015). Augmented α₁AR sensitivity may contribute mechanistically to enhanced neurovascular transduction in CKD and may explain, in part, the greater blood pressure reactivity exhibited in these patients.

Predisposing factors to heart failure in diabetic nephropathy: a look at the sympathetic nervous system hyperactivity

Diabetes mellitus (DM) and heart failure (HF) are frequent comorbidities among elderly patients. HF, a leading cause of mortality and morbidity worldwide, is characterized by sympathetic nervous system hyperactivity. The prevalence of diabetes mellitus (DM) is rapidly growing and the risk of developing HF is higher among DM patients. DM is responsible for several macro- and micro-angiopathies that contribute to the development of coronary artery disease (CAD), peripheral artery disease, retinopathy, neuropathy and diabetic nephropathy (DN) as well. Independently of CAD, chronic kidney disease (CKD) and DM increase the risk of HF. Individuals with diabetic nephropathy are likely to present a distinct pathological condition, defined as diabetic cardiomyopathy, even in the absence of hypertension or CAD, whose pathogenesis is only partially known. However, several hypotheses have been proposed to explain the mechanism of diabetic cardiomyopathy: increased oxidative stress, altered substrate metabolism, mitochondrial dysfunction, activation of renin-angiotensin-aldosterone system (RAAS), insulin resistance, and autonomic dysfunction. In this review, we will focus on the involvement of sympathetic system hyperactivity in the diabetic nephropathy.

Association of B-Type Natriuretic Peptide Level With Residual Kidney Function in Incident Peritoneal Dialysis Patients

BACKGROUND

Residual kidney function (RKF) is an important factor influencing both technique and patient survival in peritoneal dialysis (PD) patients. B-type natriuretic peptide (BNP) is considered a marker of cardio-renal syndrome. The relationship between BNP and RKF in PD patients remains unclear.

METHODS

We conducted a prospective study of 89 patients who had started and continued PD for 6 months or more in Kyushu University Hospital between June 2006 and September 2015. Participants were divided into low BNP (≤ 102.1 ng/L) and high BNP (> 102.1 ng/L) groups according to median plasma BNP level at PD initiation. The primary outcome was RKF loss, defined as 24-hour urine volume less than 100 mL. We estimated the association between BNP and RKF loss using a Kaplan-Meier method and Cox proportional hazards model and compared the rate of RKF decline between the 2 groups. To evaluate the consistency of the association, we performed subgroup analysis stratified by baseline characteristics.

RESULTS

During the median follow-up of 30 months, 30 patients lost RKF. Participants in the high BNP group had a 5.87-fold increased risk for RKF loss compared with the low BNP group after adjustment for clinical and cardiac parameters. A high plasma BNP level was more clearly associated with RKF loss in younger participants compared with older participants in subgroup analysis.

CONCLUSIONS

B-type natriuretic peptide may be a useful risk marker for RKF loss in PD patients. The clinical importance of plasma BNP level as a marker of RKF loss might be affected by age.

Renalase in Children with Glomerular Kidney Diseases

Studies suggest that renalase, a renal catecholamine-inactivating enzyme, plays a major role in the pathogenesis of kidney and cardiovascular diseases in adults. This study seeks to determine the role of renalase in children with glomerular kidney diseases. We evaluated the serum renalase, arterial stiffness, intima-media thickness, blood pressure, and clinical and biochemical parameters in 78 children (11.9 ± 4.6 years of age) with glomerulopathies such as idiopathic nephrotic syndrome (40 cases), IgA nephropathy (12 cases), Henoch-Schönlein nephropathy (12 cases), and other glomerulopathies (14 cases). The control group consisted of 38 healthy children aged 11.8 ± 3.3 years. The mean renalase was 25.74 ± 8.94 μg/mL in the glomerulopathy group, which was not significantly different from the 27.22 ± 5.15 in the control group. The renalase level did not differ among various glomerulopathies either. However, proteinuric patients had a higher renalase level than those without proteinuria (28.43 ± 11.71 vs. 24.05 ± 6.23, respectively; p = 0.03). In proteinuric patients, renalase correlated with daily proteinuria. In the entire glomerulopathy group, renalase correlated with age, systolic central blood pressure (BP), diastolic peripheral and central BP, mean peripheral and central BP; peripheral diastolic BP Z-score, glomerular filtration rate, cholesterol, triglycerides, and pulse wave velocity. We conclude that in children with glomerulopathies renalase, although basically not enhanced, may underlie blood pressure elevation and arterial damage.

Uraemia: an unrecognized driver of central neurohumoral dysfunction in chronic kidney disease?

Chronic kidney disease (CKD) carries a large cardiovascular burden in part due to hypertension and neurohumoral dysfunction - manifesting as sympathetic overactivity, baroreflex dysfunction and chronically elevated circulating vasopressin. Alterations within the central nervous system (CNS) are necessary for the expression of neurohumoral dysfunction in CKD; however, the underlying mechanisms are poorly defined. Uraemic toxins are a diverse group of compounds that accumulate as a direct result of renal disease and drive dysfunction in multiple organs, including the brain. Intensive haemodialysis improves both sympathetic overactivity and cardiac baroreflex sensitivity in renal failure patients, indicating that uraemic toxins participate in the maintenance of autonomic dysfunction in CKD. In rodents exposed to uraemia, immediate early gene expression analysis suggests upregulated activity of not only pre-sympathetic but also vasopressin-secretory nuclei. We outline several potential mechanisms by which uraemia might drive neurohumoral dysfunction in CKD. These include superoxide-dependent effects on neural activity, depletion of nitric oxide and induction of low-grade systemic inflammation. Recent evidence has highlighted superoxide production as an intermediate for the depolarizing effect of some uraemic toxins on neuronal cells. We provide preliminary data indicating augmented superoxide production within the hypothalamic paraventricular nucleus in the Lewis polycystic kidney rat, which might be important for mediating the neurohumoral dysfunction exhibited in this CKD model. We speculate that the uraemic state might serve to sensitize the central actions of other sympathoexcitatory factors, including renal afferent nerve inputs to the CNS and angiotensin II, by way of recruiting convergent superoxide-dependent and pro-inflammatory pathways.

Resistant Hypertension and Renal Nerve Denervation

Patients with resistant hypertension are a subgroup of the hypertensive population that are at even greater risk of cardiovascular outcomes. Therapeutic options for these patients are limited to antihypertensive medications. However, renal denervation (RDN) is a novel nonpharmacologic intervention that involves a catheter-based ablation of the sympathetic nerves within the renal artery wall. The procedure initially showed promise with remarkable blood pressure reductions until the pivotal SYMPLICITY HTN-3 trial failed to demonstrate superiority of RDN over control. This trial was notable for a substantial placebo effect and an attenuated response to RDN. These findings, which contradicted those of prior studies, have raised numerous questions, including whether adequate RDN occurred in those patients. Further research is planned to resolve some of these questions and to clarify the role of RDN in treating patients with resistant hypertension.

Cardio-renal syndrome

Cardio-renal syndrome is a commonly encountered problem in clinical practice. Its pathogenesis is not fully understood. The purpose of this article is to highlight the interaction between the cardiovascular system and the renal system and how their interaction results in the complex syndrome of cardio-renal dysfunction. Additionally, we outline the available therapeutic strategies to manage this complex syndrome.

Catheter-based Renal Artery Denervation for Resistant Hypertension: Promise Unfulfilled or Unsettled?

Resistant hypertension affects approximately 10-15 % of the hypertensive population and is associated with an increased occurrence of adverse cardiovascular outcomes. Recently, renal denervation (RDN) has emerged as a novel, non-pharmacologic therapy for resistant hypertension that is designed to ablate the sympathetic nerves distributed around the renal arteries, thus diminishing sympathetic nervous system activity and its influence on hypertension. RDN appeared to have a powerful BP-lowering effect in early clinical trials. However, a pivotal follow-up trial, SYMPLICITY HTN-3, showed no additional benefit of the therapy when compared with a sham procedure. Various aspects of the trial have been examined to explain this inconsistency, including a potent placebo effect and uncertainty about whether RDN actually occurred. Further research is needed to clarify the role of RDN in the management of resistant hypertension.

Preeclampsia and future cardiovascular risk: A point of view from the clearance of plasma vasoactive amines

OBJECTIVE

To summarize the reported evidence on the relationship between vasoactive amines and preeclampsia.

METHODS

A literature search was conducted in MEDLINE/PubMed and EMBASE.

RESULTS

The summarized results are as follows: (1) Menstruation can effectively eliminate vasoactive amines norepinephrine, serotonin and histamine. (2) Pregnancy increases norepinephrine production due to fetal brain development and decreases vasoactive-amine elimination due to amenorrhea. (3) Preeclampsia is associated with a low renal and/or sweating capacity, or in rare cases, with increased norepinephrine production due to maternal pheochromocytoma and fetal neuroblastoma.

CONCLUSION

Preeclampsia is mainly due to decreased excretion of norepinephrine and other vasoactive amines.

Subcutaneous nerve activity and mechanisms of sudden death in a rat model of chronic kidney disease

BACKGROUND

The mechanisms of sudden death in chronic kidney disease (CKD) remain unclear.

OBJECTIVE

The purpose of this study was to test the hypotheses that subcutaneous nerve activity (SCNA) can be used to estimate sympathetic tone in ambulatory rats and that abrupt reduction of SCNA precedes the spontaneous arrhythmic death of Cy/+ rats.

METHODS

Radiotransmitters were implanted in ambulatory normal (N = 6) and Cy/+ (CKD; N = 6) rats to record electrocardiogram and SCNA. Two additional rats were studied before and after chemical sympathectomy with 6-hydroxydopamine.

RESULTS

In normal rats, the baseline heart rate (HR) and SCNA were 351 ± 29 bpm and 5.12 ± 2.97 mV·s, respectively. SCNA abruptly increased HR by 4.31% (95% confidence interval 4.15%-4.47%). In comparison, the CKD rats had reduced baseline HR (336 ± 21 bpm, P < .01) and SCNA (4.27 ± 3.19 mV·s, P < .01). When SCNA was observed, HR increased by only 2.48% (confidence interval 2.29%-2.67%, P < .01). All Cy/+ rats died suddenly, preceded by sinus bradycardia, advanced (second- and third-degree) AV block (N = 6), and/or ventricular tachycardia or fibrillation (N = 3). Sudden death was preceded by a further reduction of SCNA (3.22 ± 2.86 mV·s, P < .01) and sinus bradycardia (243 ± 55 bpm, P < .01). Histologic studies in CKD rats showed myocardial calcification that involved the conduction system. Chemical sympathectomy resulted in progressive reduction of SCNA over 7 days.

CONCLUSION

SCNA can be used to estimate sympathetic tone in ambulatory rats. CKD is associated with reduced HR response to SCNA and conduction system diseases. Abrupt reduction of sympathetic tone precedes AV block, ventricular arrhythmia, and sudden death of CKD rats.

Apparent treatment-resistant hypertension and chronic kidney disease: another cardiovascular-renal syndrome?

To identify patients at increased risk of cardiovascular (CV) outcomes, apparent treatment-resistant hypertension (aTRH) is defined as having a blood pressure above goal despite the use of 3 or more antihypertensive therapies of different classes at maximally tolerated doses, ideally including a diuretic. Recent epidemiologic studies in selected populations estimated the prevalence of aTRH as 10% to 15% among patients with hypertension and that aTRH is associated with elevated risk of CV and renal outcomes. Additionally, aTRH and CKD are associated. Although the pathogenesis of aTRH is multifactorial, the kidney is believed to play a significant role. Increased volume expansion, aldosterone concentration, mineralocorticoid receptor activity, arterial stiffness, and sympathetic nervous system activity are central to the pathogenesis of aTRH and are targets of therapies. Although diuretics form the basis of therapy in aTRH, pathophysiologic and clinical data suggest an important role for aldosterone antagonism. Interventional techniques, such as renal denervation and carotid baroreceptor activation, modulate the sympathetic nervous system and are currently in phase III trials for the treatment of aTRH. These technologies are as yet unproven and have not been investigated in relationship to CV outcomes or in patients with CKD.

Endovascular renal denervation: a novel sympatholytic with relevance to chronic kidney disease

Endovascular renal denervation (sympathectomy) is a novel procedure developed for the treatment of resistant hypertension. Evidence suggests that it reduces both afferent and efferent sympathetic nerve activity, which may offer clinical benefit over and above any blood pressure-lowering effect. Studies have shown objective improvements in left ventricular mass, ventricular function, central arterial stiffness, central haemodynamics, baroreflex sensitivity and arrhythmia frequency. Benefits have also been seen in insulin resistance, microalbuminuria and glomerular filtration rate. In chronic kidney disease, elevated sympathetic activity has been causally linked to disease progression and cardiovascular sequelae. Effecting a marked reduction in sympathetic hyperactivity may herald a significant step in the management of this and other conditions. In this in-depth review, the pathophysiology and clinical significance of the sympatholytic effects of endovascular renal denervation are discussed.

Renin-angiotensin-aldosterone system activity in hyperthyroid cats with and without concurrent hypertension

BACKGROUND

Hypertension is present in some hyperthyroid cats at diagnosis or can develop after treatment for hyperthyroidism. Activation of the renin-angiotensin-aldosterone system (RAAS) could be involved in the pathogenesis of hypertension.

HYPOTHESIS

Hyperthyroid cats that develop hypertension before or after treatment for hyperthyroidism will have greater RAAS activation than normotensive cats.

ANIMALS

Ninety-nine hyperthyroid cats.

METHODS

Retrospective case-control study. Plasma renin activity (PRA) and plasma aldosterone concentration (PAC) were measured in untreated hyperthyroid hypertensive cats (HT-Pre group), initially normotensive hyperthyroid cats that develop hypertension after treatment (HT-Post group), and hyperthyroid cats that are normotensive (NT group). Data are presented as median [25th, 75th percentile].

RESULTS

Baseline PRA was not significantly different among the 3 groups (HT-Pre group 1.50 [0.05, 2.37] ng/mL/h, HT-Post group 0.66 [0.17, 2.31] ng/mL/h, NT group 1.11 [0.57, 2.18] ng/mL/h; P = .44). PRA decreased significantly after treatment in the NT group (1.09 [0.53, 2.47] versus 0.22 [0.05, 0.76] ng/mL/h; P < .001) and the HT-Post group (0.71 [0.17, 2.33] versus 0.28 [0.07, 0.57] ng/mL/h; P = .006). Baseline PAC was not significantly different among the 3 groups (HT-Pre group 72.2 [40.0, 145.6] pg/mL, HT-Post group 69.7 [43.3, 142.6] pg/mL, NT group 109.0 [68.2, 184.6] pg/mL; P = .10). PAC decreased significantly after treatment in the NT group (114.4 [56.6, 204.1] versus 59.5 [32.4, 98.2] pg/mL; P < .001) but did not change significantly in the HT-Post group (61.2 [44.9, 124.0] versus 58.4 [42.0, 97.7] pg/mL; P = .59).

CONCLUSIONS AND CLINICAL IMPORTANCE

RAAS activation occurs in hyperthyroid cats, but is not associated with the development of hypertension. PAC is not influenced by changes in PRA in hyperthyroid cats that develop hypertension after treatment, perhaps indicating RAAS dysfunction in these cats.

The great East Japan earthquake: blood pressure control in patients with chronic kidney disease

BACKGROUND

At 1446 on 11 March 2011, northeastern Japan was struck by a major earthquake measuring 9.0 on the Richter scale. There have been several reports of transient blood pressure increases after a major earthquake, but the impact of a major earthquake on blood pressure in chronic kidney disease (CKD) patients has not been fully investigated.

METHODS

Changes in clinic blood pressure following the earthquake were investigated in 132 hypertensive patients with stage 3 and 4 CKD who were residents of Fukushima City.

RESULTS

Both systolic and diastolic blood pressures were significantly elevated 1-3 weeks after the earthquake compared with before the earthquake (134 ± 19 mm Hg vs. 138 ± 20 mm Hg, P = 0.02 for systolic; 76 ± 13 mm Hg vs. 79 ± 12 mm Hg, P = 0.01 for diastolic), and these values returned to baseline by 5-7 weeks after the earthquake. Multiple logistic regression analysis identified male sex (odds ratio (OR), 0.35; 95% confidence interval (CI), 0.14-0.86; P = 0.02), mean blood pressure at baseline (OR, 0.92; 95% CI, 0.86-0.96; P < 0.01), and sympatholytic medications, such as α-blockers, β-blockers, or central sympatholytics (OR, 0.23; 95% CI, 0.07-0.76; P = 0.01), as independent factors related to elevation of mean blood pressure 1-3 weeks after the earthquake in CKD patients.

CONCLUSIONS

Blood pressure was significantly increased after a major earthquake in hypertensive patients with stage 3 and 4 CKD. During the first 3 weeks after the earthquake, blood pressure control was associated with the use of sympatholytic medications.

Chronic Kidney Disease and Atrial Fibrillation: A Contemporary Overview

Chronic kidney disease (CKD) is associated with substantial cardiovascular morbidity, including myocardial infarction, heart failure and stroke. Similar to CKD, atrial fibrillation (AF) is a prevalent arrhythmia that increases risk for both stroke and overall mortality. Recent studies demonstrate that both prevalence and incidence of AF is higher in patient with versus without renal impairment and risk for developing AF increases as renal function worsens. Potential mechanisms for the higher burden of AF in CKD patients include but are not limited to augmented sympathetic tone, activation of the renin-angiotensin-aldosterone system and myocardial remodeling. Similar to the general population, AF confers an increased risk for both stroke and overall mortality in the CKD population. The safety and efficacy of antithrombotic therapy across the spectrum of CKD remains unknown, however, as patients with advanced renal failure are frequently excluded from randomized trials. While treatment with vitamin K antagonists appears to reduce ischemic complications without significant bleeding harm in patients with mild to moderate CKD and AF, the risk benefit ratio of anticoagulation among thosewith advanced renal failure on dialysis requires further investigation. Prospective, randomized trials are war ranted to define the impact of antithrombotic therapy on reducing stroke risk in patients with both AF and CKD.

Sympathoexcitation by brain oxidative stress mediates arterial pressure elevation in salt-induced chronic kidney disease

Hypertension is very prevalent in chronic kidney disease and critical for its prognosis. Sympathoexcitation and oxidative stress have been demonstrated to be involved in chronic kidney disease. We have shown previously that sympathoexcitation by brain oxidative stress mediates arterial pressure elevation in the salt-sensitive hypertension model, Dahl salt-sensitive rats. Thus, we investigated whether sympathoexcitation by excessive brain oxidative stress could contribute to arterial pressure elevation in salt-induced chronic kidney disease model rats. Young (3-week-old) male Sprague-Dawley rats were randomly assigned to a uninephrectomy or sham operation and then subjected to either a normal salt (0.5%) or high-salt (8.0%) diet for 4 weeks. The young salt-loaded uninephrectomized rats exhibited sympathoexcitation, hypertension, and renal injury, proteinuria and global glomerulosclerosis together with tubulointerstitial damage. Under urethane anesthesia and artificial ventilation, renal sympathetic nerve activity, arterial pressure, and heart rate decreased to a greater degree in the salt-loaded uninephrectomized rats than in the nonsalt-loaded uninephrectomized rats and the salt-loaded or nonsalt-loaded sham-operated rats, when Tempol, a membrane-permeable superoxide dismutase mimetic, was infused acutely into the lateral cerebral ventricle. Oxidative stress in the hypothalamus, measured by lucigenin chemiluminescence, was also significantly greater. Furthermore, in the salt-loaded uninephrectomized rats, antioxidant treatment with chronic intracerebroventricular Tempol decreased sympathetic nerve activity and arterial pressure, which, in turn, led to a decrease in renal damage. Similar effects were elicited by treatment with oral moxonidine, the central sympatholytic agent. In conclusion, sympathoexcitation by brain oxidative stress may mediate arterial pressure elevation in salt-induced chronic kidney disease.

Early sympathetic activation in the initial clinical stages of chronic renal failure

Direct and indirect indices of neuroadrenergic function have shown that end-stage renal disease is characterized by a marked sympathetic overdrive. It is unknown, however, whether this phenomenon represents a peculiar feature of end-stage renal disease or whether it is also detectable in the early clinical phases of the disease. The study has been performed in 73 hypertensive patients, of which there were 42 (age: 60.7±1.8 years, mean±SEM) with a stable moderate chronic renal failure (mean estimated glomerular filtration rate: 40.7 mL/min per 1.73 m2, MDRD formula) and 31 age-matched controls with a preserved renal function. Measurements included anthropometric variables, sphygmomanometric and beat-to-beat blood pressure, heart rate (ECG), venous plasma norepinephrine (high-performance liquid chromatography), and efferent postganglionic muscle sympathetic nerve activity (microneurography, peroneal nerve). For similar anthropometric and hemodynamic values, renal failure patients displayed muscle sympathetic nerve activity values significantly and markedly greater than controls (60.0±2.1 versus 45.7±2.0 bursts per 100 heartbeats; P<0.001). Muscle sympathetic nerve activity showed a progressive and significant increase from the first to the fourth quartile of the estimated glomerular filtration rate values (first: 41.0±2.7; second: 51.9±1.7; third: 59.8±3.0; fourth: 61.9±3.3 bursts per 100 heartbeats), the statistical significance (P<0.05) between groups being maintained after adjustment for confounders. In the population as a whole, muscle sympathetic nerve activity was significantly and inversely correlated with the estimated glomerular filtration rate (r=-0.59; P<0.0001). Thus, adrenergic activation is a phenomenon not confined to advanced renal failure but already detectable in the initial phases of the disease. The sympathetic overdrive parallels the severity of the renal failure, state and, thus, it might participate, in conjunction with other factors, at the disease progression.

Sympathetic activation in chronic renal failure

The potential involvement of sympathetic overactivity has been neglected in this population despite accumulating experimental and clinical evidence suggesting a crucial role of sympathetic activation for both progression of renal failure and the high rate of cardiovascular events in patients with chronic kidney disease. The contribution of sympathetic neural mechanisms to the occurrence of cardiac arrhythmias, the development of hypertension, and the progression of heart failure are well established; however, the exact mechanisms contributing to heightened sympathetic tone in patients with chronic kidney disease are unclear. This review analyses potential mechanisms underlying sympathetic activation in chronic kidney disease, the range of adverse consequences associated with this activation, and potential therapeutic implications resulting from this relationship.

Effects of nitric oxide synthase inhibition and l-arginine on renal haemodynamics in young patients at high cardiovascular risk

BACKGROUND

Aging and a variety of cardiovascular risk factors are associated with oxidative stress and impaired endothelial function. Whether such an association is already evident in the renal vascular bed in young patients at high cardiovascular risk has not yet been determined.

METHODS

We compared renal haemodynamics in 23 young (age 30+/-5 years) male patients at high cardiovascular risk with impaired lipid metabolism and elevated blood pressure with 23 matched, healthy control subjects (age 28+/-3 years) without cardiovascular risk factors at baseline and following infusions of the nitric oxide (NO) synthase inhibitor N(G)-monomethyl-L-arginine (L-NMMA: 4.25mg/kg), the substrate of NO synthase L-arginine (100mg/kg) and the antioxidant Vitamin C (3g, co-infused with L-arginine 100mg/kg).

RESULTS

Baseline renal haemodynamics did not differ between the two groups. Infusion of L-NMMA decreased renal plasma flow (RPF) in both groups to a similar extent (-113+/-95 ml/min versus -128+/-133 ml/min, p=NS). The response of RPF to infusion of L-arginine was more pronounced in high risk patients than in control subjects (+123+/-64.4 ml/min versus +75.6+/-60.2 ml/min, p=0.012) and further exaggerated during co-infusion of L-arginine and Vitamin C (+299+/-164 ml/min versus +175+/-148 ml/min, p=0.003).

CONCLUSIONS

Basal NO activity of the renal vasculature appears to be unaltered in young patients at high cardiovascular risk. However, the greater response of RPF to L-arginine and to Vitamin C co-infused with L-arginine in these young patients suggests that decreased substrate availability for NO synthase and oxidative stress are key factors for alterations in endothelium-dependent vasodilation of the renal vasculature in this young high risk group of patients.

Sympathetic hyperactivity in hypertensive chronic kidney disease patients is reduced during standard treatment

Standard treatment in chronic kidney disease (CKD) patients includes an angiotensin-converting enzyme inhibitor or angiotensin II receptor blocker. CKD is often characterized by sympathetic hyperactivity. This study investigates the prevalence of sympathetic hyperactivity (quantified by assessment of muscle sympathetic nerve activity [MSNA]) in a sizable group of patients with CKD and assessed whether chronic angiotensin-converting enzyme inhibitor or angiotensin II receptor blocker normalizes increased MSNA. In 74 CKD patients (creatinine clearance 54+/-31 mL/min), MSNA, blood pressure, and plasma renin activity were measured in the absence of antihypertensive drugs except for diuretics. In a subgroup of 31 patients, another set of measurements was obtained after > or =6 weeks of enalapril (10 mg PO), losartan (100 mg PO), or eprosartan (600 mg PO). Patients as compared with control subjects (n=82) had higher mean arterial pressure (113+/-13 versus 89+/-7 mm Hg), MSNA (31+/-13 versus 19+/-7 bursts per minute), and log plasma renin activity (2.67+/-036 versus 2.40+/-0.32 fmol/L per second; all P<0.001). During angiotensin-converting enzyme inhibitor or angiotensin II receptor blocker therapy (n=31), mean arterial pressure (115+/-11 to 100+/-9 mm Hg) and MSNA (33+/-11 to 25+/-9 bursts per minute) decreased (both P<0.01) but were still higher than in control subjects (both P<0.01). Multiple regression analysis identified age and plasma renin activity as predictive for MSNA. In conclusion, sympathetic hyperactivity occurs in a substantial proportion of hypertensive CKD patients. Angiotensin-converting enzyme inhibitor or angiotensin II receptor blocker treatment reduces but does not normalize MSNA.

Neurogenic factors in renal hypertension

Hypertension is very common in patients with chronic renal failure and contributes to cardiovascular morbidity and mortality. Several mechanisms may contribute to hypertension in these patients, but recently a large body of evidence supports the notion that activation of the sympathetic nervous system (SNS) may play a very important role. In rats with 5/6 nephrectomy, the turnover rate of norepinephrine was increased in brain nuclei involved in the noradrenergic control of blood pressure, and dorsal rhizotomy prevented hypertension. Studies in human subjects with chronic renal failure and hypertension have also shown increased peripheral SNS activity measured my microneurography in the peroneal nerve and normalization with nephrectomy. In all, these studies indicate that renal injuries may activate renal afferent pathways that connect with integrative brain structures in SNS activity and blood pressure. We have also shown that central SNS activity is modulated by local expression of nitric oxide, which, in turn, is regulated by interleukin-1b.

Adrenomedullin inhibits the pressor effects and decrease in renal blood flow induced by norepinephrine or angiotensin II in anesthetized rats

Adrenomedullin (AM), a hypotensive peptide originally isolated from human pheochromocytoma, has been reported to regulate renal functions. In patients with glomerulonephritis, the serum levels of AM are elevated as well as hypertensive agents norepinephrine (NE) and angiotensin II (AII). The effects of AM on the NE- or AII-induced pressor effects and renal blood flow responses, however, are not well clarified. We examined the effects of AM on blood pressure and renal blood flow induced by NE or AII in anesthetized rats. Arterial blood pressure and renal blood flow were measured using a calibrated pressure transducer and a laser Doppler flowmeter, respectively. Drugs were injected into the tail vein with a syringe. Intravenous administration of AM (1-3 nmol/kg) decreased the arterial blood pressure in anesthetized rats in a dose-dependent manner, whereas it did not affect the renal blood flow. NE or AII administration in anesthetized rats caused both increases in blood pressure and decreases in renal blood flow. Simultaneous administration of AM with NE or All prevented the increasing effects of blood pressure and inhibited the decreases in renal blood flow caused by NE or AII. These findings suggest that AM may have a protective role against the pressor effects and decrease in renal blood flow caused by NE or AII.

Complications of chronic renal insufficiency: beyond cardiovascular disease

The less rigorous attention to the management of the complications of chronic renal insufficiency (CRI) and its comorbid conditions has potentially tragic consequences. In fact, with early recognition and intervention, many of the complications of CRI and its comorbid conditions can be ameliorated or prevented. We review here the most prevalent, troublesome, and potentially preventable complications and comorbidities of CRI with a view toward developing high-quality, cost-effective strategies for delivering early interventional care. Complications of CRI include malnutrition, anemia, disorders of divalent ion metabolism and osteodystrophy, metabolic acidosis, and dyslipidemia. Important comorbid conditions of CRI are hypertension, diabetes mellitus, and cardiovascular disease. Clinical intuition suggests that early intervention will avert morbidity related to the hypoalbuminemia and other nutritional disorders of CRI, the metabolic acidosis, and the dyslipidemias, but prospective data are lacking at present. Correction of anemia, usually with recombinant human erythropoietin, may be key to the prevention of cardiac disease and other comorbidities of CRI. Incipient disorders of bone and mineral metabolism are managed prospectively using such measures as protein restriction to reduce phosphorus intake, phosphate binders, calcium supplementation, and vitamin D analogues. Hypertension, whatever its original etiology, is clearly an important risk factor for the progression of kidney failure and for the development of diffuse vascular disease; appropriate and aggressive treatment is essential. In patients with diabetic nephropathy, the principles of both primary and secondary prevention have been validated in several large trials of glycemic and blood pressure control. The seeds of these insidious, challenging, and costly comorbid conditions are sown very early in CRI, at a time when they are-in theory-most amenable to intervention. We therefore must be as proactive as possible in the timely implementation of relatively simple therapies that have the potential to prevent some of these adverse outcomes of CRI.

Ocular lesions associated with systemic hypertension in cats: 69 cases (1985-1998)

OBJECTIVE

To characterize clinical and clinicopathologic findings, response to treatment, and causes of systemic hypertension in cats with hypertensive retinopathy.

DESIGN

Retrospective study.

ANIMALS

69 cats with hypertensive retinopathy.

PROCEDURE

Medical records from cats with systemic hypertension and hypertensive retinopathy were reviewed.

RESULTS

Most cats (68.1%) were referred because of vision loss; retinal detachment, hemorrhage, edema, and degeneration were common findings. Cardiac abnormalities were detected in 37 cats, and neurologic signs were detected in 20 cats. Hypertension was diagnosed concurrently with chronic renal failure (n = 22), hyperthyroidism (5), diabetes mellitus (2), and hyperaldosteronism (1). A clearly identifiable cause for hypertension was not detected in 38 cats; 26 of these cats had mild azotemia, and 12 did not have renal abnormalities. Amlodipine decreased blood pressure in 31 of 32 cats and improved ocular signs in 18 of 26 cats.

CONCLUSIONS AND CLINICAL RELEVANCE

Retinal lesions, caused predominantly by choroidal injury, are common in cats with hypertension. Primary hypertension in cats may be more common than currently recognized. Hypertension should be considered in older cats with acute onset of blindness; retinal edema, hemorrhage, or detachment; cardiac disease; or neurologic abnormalities. Cats with hypertension-induced ocular disease should be evaluated for renal failure, hyperthyroidism, diabetes mellitus, and cardiac abnormalities. Blood pressure measurements and funduscopic evaluations should be performed routinely in cats at risk for hypertension (preexisting renal disease, hyperthyroidism, and age > 10 years). Amlodipine is an effective antihypertensive agent in cats.

Insulin resistance and hyperinsulinemia are already present in patients with incipient renal disease

In uremic patients resistance to the action of insulin has been documented, but it is not known at what stage of renal disease it appears. We therefore examined 29 patients with IgA glomerulonephritis (IgAGN) and 21 patients with adult polycystic kidney disease (ADPKD) in different stages of renal failure, and in addition, healthy age-matched subjects. Insulin sensitivity and other variables of glucose metabolism were assessed using a frequent sampling intravenous glucose tolerance test (minimal-model technique). Glomerular filtration rate (GFR) was assessed in renal patients using the inulin-clearance technique. Mean insulin sensitivity index (SI), that is, insulin sensitivity, was significantly lower (P < 0.001) in all patients combined than in matched healthy subjects (N = 16; 14 males, mean age 42 +/- 3 years; mean SI 8.6 +/- 0.8 min-1 uU/ml). The mean SI was not significantly different in patients with renal disease of immune (IgAGN) or non-immune (ADPKD) origin, and it was not correlated with GFR (r = 0.01, P < 0.52), intact PTH (r = -0.23, P < 0.11) or calcitriol concentration (r = -0.03, P < 0.82). Consequently, the mean SI was similar in renal patients with GFR within the normal range (N = 19; 17 males, mean age 41 +/- 2 years; mean GFR 119 +/- 5 ml/min/1.73 m2; 5.1 +/- 0.7 min-1 uU/ml), in patients with mild to moderate renal failure (N = 16; 15 males, 46 +/- 3 years; 67 +/- 4 ml/min/1.73 m2; 5.1 +/- 0.7 min-1 microU/ml) and in patients with advanced renal failure (N = 15; 13 males, 46 +/- 3 years; 25 +/- 2 ml/min/1.73 m2; 4.7 +/- 0.6 min-1 uU/ml). Mean fasted plasma insulin concentration, the area under the curve for plasma insulin concentration (AUC) and total insulin delivery (TID) during the glucose tolerance test were significantly higher in patients than in healthy subjects, reflecting hyperinsulinemia in renal patients. Further, fasted plasma insulin concentration (r = -0.32, P < 0.009), AUC (r = -0.62, P < 0.0001) and TID (r = -0.34, P < 0.004) in patients were significantly correlated with insulin sensitivity (SI). The present data document that insulin resistance and concomitant hyperinsulinemia are present early in the course of renal disease, that is, even in patients with GFR within the normal range, irrespective of the type of renal disease. This observation may have potential implications with respect to the high cardiovascular morbidity and mortality in patients with renal disease.

Neural control of renal function

The renal nerves are the communication link between the central nervous system and the kidney. In response to multiple peripheral and central inputs, efferent renal sympathetic nerve activity is altered so as to convey information to the major structural and functional components of the kidney, the vessels, glomeruli, and tubules, each of which is innervated. At the level of each of these individual components, information transfer occurs via interaction of the neurotransmitter released at the sympathetic nerve terminal-neuroeffector junction with specific postjunctional receptors coupled to defined intracellular signaling and effector systems. In response to normal physiological stimuli, changes in efferent renal sympathetic nerve activity contribute importantly to homeostatic regulation of renal blood flow, glomerular filtration rate, renal tubular epithelial cell solute and water transport, and hormonal release. Afferent input from sensory receptors located in the kidney participates in this reflex control system via renorenal reflexes that enable total renal function to be self-regulated and balanced between the two kidneys. In pathophysiological conditions, abnormal regulation of efferent renal sympathetic nerve activity contributes significantly to the associated abnormalities of renal function which, in turn, are of importance in the pathogenesis of the disease.

Secondary hypertension: evaluation and treatment

Most patients with hypertension in the United States have essential (primary) hypertension (95%), the cause of which is unknown. The remaining 5% of adults with hypertension have the secondary form of hypertension, the cause and pathophysiologic process of which are known. Internists and other primary care physicians refer to this as treatable or curable hypertension, because the hypertension can be managed or even controlled with medications. Similarly, the condition is called surgical hypertension by surgeons in the belief that once the cause is determined and identified, surgical intervention will result in cure of hypertension. Secondary causes of hypertension include renal parenchymal disease, renovascular diseases, coarctation of the aorta, Cushing's syndrome, primary hyperaldosteronism, pheochromocytoma, hyperthyroidism, and hyperparathyroidism. Occasionally included in this category are alcohol- and oral contraceptive-induced hypertension and hypothyroidism, but these conditions are not discussed herein. The evaluation of secondary hypertension is of interest and can bring together different facets of anatomy, physiology, pharmacology, and radiology in the medical and surgical treatment of these disorders. Despite enthusiasm that can be generated in the evaluation of these conditions, evaluation can be expensive and should not be conducted for all patients with hypertension. Features that aid in the diagnosis of secondary hypertension include the following: 1. Onset of hypertension before the age of 20 or after the age of 50 years. The presence of hypertension at a young age may suggest coarctation of the aorta, fibromuscular dysplasia, or an endocrine disorder. Hypertension found for the first time after the age of 50 years may suggest the presence of renovascular hypertension caused by atherosclerosis. 2. Markedly elevated blood pressure or hypertension with severe end-organ damage, as in grade III or IV retinopathy. These findings suggest the presence of renovascular hypertension or pheochromocytoma. 3. Specific body habitus and ancillary physical findings. For example, truncal obesity and purple striae occur with hypercortisolism, and exophthalmos is associated with hyperthyroidism. 4. Resistant or refractory hypertension (poor response to medical therapy usually necessitating use of more than three antihypertensive medications from three different classes). 5. Specific biochemical test that suggest the existence of certain disorders, such as hypercalcemia in hyperparathyroidism, hyperglycemia in Cushing's syndrome and pheochromocytoma, and unprovoked hypokalemia with renin-producing tumors, primary hyperaldosteronism, or renin-mediated renovascular hypertension. 6. Other characteristics that may suggest secondary hypertension such as abdominal diastolic bruits (renovascular hypertension), decreased femoral pulses (coarctation of the aorta), or bitemporal hemianopias (Cushing's disease). A combination of a good history and physical examination, astute observation, and accurate interpretation of available data usually are helpful in the diagnosis of a specific causation.

Age-related changes in muscle sympathetic nerve activity in essential hypertension

To investigate the pathophysiological role of the sympathetic nervous system in essential hypertension, this study recorded the muscle sympathetic nerve activity (MSNA) of the tibial nerve and examined the age-related changes in patients with essential hypertension and in normotensive persons. There were 43 normotensive subjects (16-69 years old) and 63 patients with essential hypertension (18-67 years old) in the study. The MSNA at rest, recorded by microneurography, was evaluated by burst rate (bursts/min), burst incidence (bursts/100 heart beats), and spike frequency (spikes/min). The MSNA recording showed a high reproducibility with a correlation coefficient of 0.86 (p less than 0.01) in repeated studies. The MSNA was significantly greater in the hypertensive patients than in the normotensive subjects, irrespective of activity units (p less than 0.01), and this finding was consistent in the young (30 years old or less), middle-aged (31-50 years old), and old groups (51 years old or more). Furthermore, MSNA showed a significant positive correlation with age both in the normotensive subjects (r = 0.43, p less than 0.01 for burst rate; r = 0.49, p less than 0.01 for burst incidence; and r = 0.50, p less than 0.01 for spike frequency) and in the hypertensive patients (r = 0.40, p less than 0.01 for burst rate; r = 0.44, p less than 0.01 for burst incidence; and r = 0.40, p less than 0.01 for spike frequency).(ABSTRACT TRUNCATED AT 250 WORDS)

Hypertension in chronic idiopathic glomerulonephritis: analysis of 311 biopsied patients

Prevalence of hypertension and relation of hypertension to renal function, type of glomerulonephritis or histological features were evaluated in 311 patients with idiopathic chronic glomerulonephritis. The overall prevalence of hypertension was 49.8%. At least in women, prevalence of hypertension was increased even at serum creatinine levels less than 1.1 mg dl-1 compared with the local general population. Prevalence of hypertension was 2.12 and 8.6 fold higher at serum creatinine 1.1-1.4 mg dl-1 in males and females respectively. In patients with untreated hypertension, a relation was found between mean blood pressure and subsequent decline of estimated GFR. Furthermore, in patients with arterial sclerosis, but not in patients without, a significant relation was found between blood pressure and subsequent increase in serum creatinine.

Renal and hormonal effects of alpha 1-adrenoceptor blockade by bunazosin in essential hypertension

The renal and hormonal effects of the alpha 1-adrenoceptor blocker bunazosin were examined in 6 patients with essential hypertension. Oral bunazosin for 4 to 12 weeks significantly decreased mean blood pressure by 10%, increased effective renal blood flow and creatinine clearance by 34% and 37%, respectively, the plasma norepinephrine concentration was elevated by 60%, and the plasma atrial natriuretic peptide level was lowered by 22%. The plasma renin activity and aldosterone concentration were unchanged. Thus, a moderate reduction in blood pressure was produced by bunazosin treatment while maintaining renal perfusion.

Hormonal and renal effects of atrial natriuretic peptide in patients with secondary hypertension

To investigate the involvement of atrial natriuretic peptide (ANP) in secondary hypertension, we examined hormonal and renal responses to ANP infusion (0.025 microgram/kg/min) in 27 patients with renal parenchymal hypertension, 10 with primary aldosteronism, 8 with renovascular hypertension, and 15 normotensive subjects. The preinfusion plasma concentration of ANP was significantly higher in patients with renal parenchymal hypertension (120 pg/ml, p less than 0.01) and in patients with primary aldosteronism (98 pg/ml, p less than 0.05) than in the normotensive subjects (40 pg/ml), but it was not greater than in the patients with renovascular hypertension (73 pg/ml, NS). In the patients with renal parenchymal hypertension, plasma ANP correlated negatively with creatinine clearance (r = -0.76, p less than 0.001). Mean blood pressure (-5%, p less than 0.01) and plasma aldosterone (-40%, p less than 0.001) decreased to a similar degree in the four groups during ANP infusion. However, an increase in urinary sodium excretion caused by ANP was higher in the hypertensive than in the normotensive patients (+250% vs. +70%, p less than 0.01) and correlated positively with mean blood pressure during ANP infusion (r = 0.47, p less than 0.001). The removal of adenomas in the patients with primary aldosteronism significantly lowered both plasma levels of ANP and cyclic guanosine 2',3'-monophosphate and reduced an increase in sodium excretion during ANP infusion, whereas the responses of blood pressure and plasma aldosterone to ANP infusion were not altered by the operation. Thus, these results suggest that elevated ANP secretion and increased natriuretic responses to ANP may modify the blood pressure and body fluid volume status in some types of secondary hypertension.

Plasma and urinary catecholamines as related to renal function in man

To assess the relationship between renal plasma flow (ERPF) or glomerular filtration rate (GFR) and the levels of norepinephrine (NE) or epinephrine (E) in plasma or urine in the presence of progressive degrees of non-oliguric renal functional impairment, these variables were assessed simultaneously in 18 normal subjects, 72 with parenchymal kidney disease and 14 with essential hypertension. ERPF and GFR were lower (P less than 0.01 to 0.001) in the groups with renal disease (mean +/- SD, 340 +/- 230 and 68 +/- 43 ml/min/1.73 m2, respectively) or essential hypertension (434 +/- 101 and 97 +/- 25 ml/min/1.73 m2) than normal subjects (597 +/- 133 and 118 +/- 14 ml/min/1.73 m2). Plasma and urinary NE and E did not differ significantly among groups and were unrelated with ERPF or GFR (range 4 to 160 ml/min/1.73 m2), except for reduced (P less than 0.001) urinary NE and E excretion in the presence of a GFR less than 20 ml/min. Subgroups with renal disease and a normal (N = 39) or high blood pressure (N = 33) also were comparable in their plasma and urinary NE and E, while ERPF and GFR tended to be lower in hypertensive patients. It is concluded that a chronic reduction in excretory kidney function may have no relevant impact on circulating levels of NE and E per se, although their urinary excretion falls distinctly at the stage of advanced renal failure. These aspects deserve consideration when pathogenetic or diagnostic studies of catecholamines are performed in normotensive or hypertensive patients with impaired kidney function.

High level of adrenal catecholamines in hypertensive subjects with impaired renal function

Contents of catecholamines were determined in 46 adrenal specimens removed from subjects without adrenal disease. These subjects were allocated in a retrospective conformation to two points: one for renal function and another for blood pressure. Based on the findings, elevated adrenal catecholamines associated with hypertension appear to impair renal function in man.

Relationship of angiotensin II, aldosterone, arginine vasopressin, adrenaline and noradrenaline in plasma, blood and extracellular volumes to blood pressure in chronic glomerulonephritis

Blood volume, extracellular volume, blood pressure and the plasma levels of angiotensin II, aldosterone, adrenaline, noradrenaline and arginine vasopressin were determined in sixteen normotensive (group 1) and thirteen hypertensive patients (group 2) with chronic glomerulonephritis and in eleven normotensive control subjects (group 3). Blood volume and extracellular volume did not differ between the groups and no significant differences were found in any of the hormones measured when comparing group 1 or group 2 with group 3. In the hypertensives but not in the normotensives or control subjects, a highly significant positive correlation was found between diastolic blood pressure and blood volume (rho = 0.75, P less than 0.01) and between diastolic blood pressure and extracellular volume (rho = 0.74, P less than 0.01). Blood volume and extracellular volume correlated (P less than 0.05) in each of the groups. In conclusion, although no expansion of either blood or extracellular volume was found in chronic glomerulonephritis, a positive volume-pressure relationship could be demonstrated in hypertensive patients suggesting a role of volume factors in the pathogenesis in early stage chronic glomerulonephritis. The study does not give support to a major role of either angiotensin II, arginine vasopressin or catecholamines in the maintenance of nonmalignant hypertension in early stage chronic glomerulonephritis.

Dissociation of renin and noradrenaline release in the renal circulation. Studies on patients with renal hypertension

Plasma renin activity (PRA) and noradrenaline concentration (NA) were measured in the renal veins (V) and arterial blood (A) in 30 patients investigated for renin-mediated hypertension. Both PRA and NA concentrations in arterial blood were above our reference limits and they were positively correlated. In 18 of the patients renin secretion was unilateral from the diseased side. Their renal vein NA concentration was always higher on that side, compared to the contralateral one, but there were V-A gradients for NA on both sides in all but two cases. In 15 of the patients with such lateralisation of renin secretion the changes of PRA and NA V-A gradients were determined 30-60 min after an i.v. injection of dihydralazine. Both PRA and NA increased more markedly in the renal vein on the affected side where the estimated renal plasma flow was lower than on the contralateral side. The NA gradients increased less than the PRA gradients when changes on the renin secreting side were compared in patients with proven increase of renin secretion. We conclude that patients with renal hypertension have a high sympathetic nervous activity as evidenced by increased plasma NA concentrations and (V-A) gradients for NA on both sides. The release of NA into the renal circulation in renin mediated hypertension is thus not invariably accompanied by renin release. The higher renal vein NA concentration on the involved renin secreting side is explained by reduced RPF on this side.