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ELife May 2022Internephron interaction is fundamental for kidney function. Earlier studies have shown that nephrons signal to each other, synchronize over short distances, and...
Internephron interaction is fundamental for kidney function. Earlier studies have shown that nephrons signal to each other, synchronize over short distances, and potentially form large synchronized clusters. Such clusters would play an important role in renal autoregulation, but due to the technological limitations, their presence is yet to be confirmed. In the present study, we introduce an approach for high-resolution laser speckle imaging of renal blood flow and apply it to estimate the frequency and phase differences in rat kidney microcirculation under different conditions. The analysis unveiled the spatial and temporal evolution of synchronized blood flow clusters of various sizes, including the formation of large (>90 vessels) and long-lived clusters (>10 periods) locked at the frequency of the tubular glomerular feedback mechanism. Administration of vasoactive agents caused significant changes in the synchronization patterns and, thus, in nephrons' co-operative dynamics. Specifically, infusion of vasoconstrictor angiotensin II promoted stronger synchronization, while acetylcholine caused complete desynchronization. The results confirm the presence of the local synchronization in the renal microcirculatory blood flow and that it changes depending on the condition of the vascular network and the blood pressure, which will have further implications for the role of such synchronization in pathologies development.
Topics: Animals; Kidney; Kidney Glomerulus; Microcirculation; Nephrons; Rats; Renal Circulation
PubMed: 35522041
DOI: 10.7554/eLife.75284 -
PloS One 2019Intrarenal Doppler ultrasonography is a non-invasive method to evaluate the renal blood flow in patients with renal arterial stenosis as well as chronic kidney diseases...
Intrarenal Doppler ultrasonography is a non-invasive method to evaluate the renal blood flow in patients with renal arterial stenosis as well as chronic kidney diseases (CKD). Until recently, the relationship between ultrasonography findings and CKD stage has not been fully understood. Overall, 162 patients with CKD without apparent renal arterial stenosis were included in this study, and the pulsed-wave Doppler ultrasonography findings were evaluated in terms of the following parameters: peak systolic velocity (PSV), end-diastolic velocity (EDV), and resistive index (RI) at the renal arterial trunk, hilum, segmental, and interlobar regions. Age showed a significant negative correlation with the estimated glomerular filtration rate (eGFR), kidney size, and aortic PSV. Additionally, age showed a significant positive correlation with RI in all 4 regions. The eGFR showed a positive correlation with the aortic PSV and kidney size, but a negative correlation with RI. Both age and eGFR were found to be independently associated with aortic blood flow. On the intrarenal ultrasound, EDV and RI showed stronger correlations with eGFR than PSV, suggesting that the former indices would be better markers of renal function. In particular, the interlobar EDV was found to be the best index that reflects renal function. Although the RI is also a good marker of renal function, it is confounded by age; thus, its utility would be weaker than that of the EDV. In conclusion, intrarenal pulsed-wave Doppler ultrasonography is a useful tool to estimate and evaluate the renal function; the interlobar EDV may be the best index to estimate the effective perfusion and filtration of the kidneys.
Topics: Blood Flow Velocity; Female; Glomerular Filtration Rate; Heart Function Tests; Hemodynamics; Humans; Kidney; Male; Middle Aged; Renal Circulation; Renal Insufficiency, Chronic; Ultrasonography, Doppler; Vascular Resistance
PubMed: 31454365
DOI: 10.1371/journal.pone.0221244 -
Scientific Reports Dec 2021The aim of this study was to evaluate renal hemodynamics, routine clinical and laboratory parameters used to estimate renal function, and clinical evolution during six...
The aim of this study was to evaluate renal hemodynamics, routine clinical and laboratory parameters used to estimate renal function, and clinical evolution during six months in bitches with mammary carcinomas that underwent mastectomy and were treated (TG) or not (CG) with carprofen for three months after surgery. Twenty-six bitches with mammary carcinoma were equally distributed into TG that received carprofen 4.4 mg/kg/day for 90 days and CG that did not receive anti-inflammatory medication. Renal artery Doppler flowmetry, contrast-enhanced ultrasound (CEUS) of renal parenchyma, haematological, biochemical and clinical analyses were obtained once a month. These data were compared between groups and time via analysis of variance (ANOVA) in a completely randomized design with repeated measures (P < 0.05). On B-mode ultrasound, the area of the renal artery was greater (P = 0.0003) in the TG. Regarding laboratory findings, haematocrit and haemoglobin were similar in both groups, showing a significant and gradual increase after three months of treatment; MCV, MHC, and MCHC were increased (P < 0.05) and lymphocyte and band counts decreased (P < 0.05) in the TG. Regarding biochemical tests, ALT was the only parameter with a significant difference, being higher (P = 0.0272) in the treated group. It can be concluded that the use of carprofen for 90 days causes minimal changes in renal perfusion, erythrocyte parameters and ALT activity, and reduces the proportion of blood inflammatory cells. Therefore, use of this medication can be carried out safely in patients who require auxiliary cancer treatment.
Topics: Animals; Carbazoles; Carcinoma; Dog Diseases; Dogs; Female; Kidney; Mammary Glands, Animal; Mammary Neoplasms, Animal; Renal Circulation; Time Factors; Ultrasonography, Doppler
PubMed: 34857853
DOI: 10.1038/s41598-021-02781-3 -
Journal of Applied Physiology... Apr 2023The sympathetic nervous system (SNS) has a critical role in continuously coordinating responses to stimuli internal and external to the human body by appropriately... (Review)
Review
The sympathetic nervous system (SNS) has a critical role in continuously coordinating responses to stimuli internal and external to the human body by appropriately modulating the activity of the organs it innervates. The SNS is activated in response to various physiological stressors, including exercise, which can involve a significant increase in SNS activity. An increase in SNS activity directed toward the kidneys causes vasoconstriction of afferent arterioles within the kidneys. This sympathetically mediated renal vasoconstriction decreases renal blood flow (RBF), causing significant blood flow redistribution toward active skeletal muscles during exercise. In research studies, different modes, intensities, and durations of exercise have been used to investigate the sympathetically mediated RBF response to exercise, and several methodological approaches have been used to quantify RBF. Doppler ultrasound provides noninvasive, continuous, real-time measurements of RBF and has emerged as a valid and reliable technique to quantify RBF during exercise. This innovative methodology has been applied in studies in which the RBF response to exercise has been examined in healthy young and older adults and patient populations such as those with heart failure and peripheral arterial disease. This valuable tool has enabled researchers to produce clinically relevant findings that have furthered our understanding of the effect of SNS activation on RBF in populations of health and disease. Therefore, the focus of this narrative review is to highlight the use of Doppler ultrasound in research studies that have provided important findings furthering our knowledge of the impact of SNS activation on RBF regulation in humans.
Topics: Humans; Aged; Renal Circulation; Exercise; Kidney; Hemodynamics; Vasoconstriction; Ultrasonography, Doppler
PubMed: 36892892
DOI: 10.1152/japplphysiol.00392.2022 -
Experimental Physiology Apr 2015What is the topic of this review? This review describes the role of renal nerves as the key carrier of signals from the kidneys to the CNS and vice versa; the brain and... (Review)
Review
What is the topic of this review? This review describes the role of renal nerves as the key carrier of signals from the kidneys to the CNS and vice versa; the brain and kidneys communicate through this carrier to maintain homeostasis in the body. What advances does it highlight? Whether renal or autonomic dysfunction is the predominant contributor to systemic hypertension is still debated. In this review, we focus on the role of the renal nerves in a model of renovascular hypertension. The sympathetic nervous system influences the renal regulation of arterial pressure and body fluid composition. Anatomical and physiological evidence has shown that sympathetic nerves mediate changes in urinary sodium and water excretion by regulating the renal tubular water and sodium reabsorption throughout the nephron, changes in the renal blood flow and the glomerular filtration rate by regulating the constriction of renal vasculature, and changes in the activity of the renin-angiotensin system by regulating the renin release from juxtaglomerular cells. Additionally, renal sensory afferent fibres project to the autonomic central nuclei that regulate blood pressure. Hence, renal nerves play a key role in the crosstalk between the kidneys and the CNS to maintain homeostasis in the body. Therefore, the increased sympathetic nerve activity to the kidney and the renal afferent nerve activity to the CNS may contribute to the outcome of diseases, such as hypertension.
Topics: Animals; Blood Pressure; Central Nervous System; Humans; Hypertension; Kidney; Renal Circulation; Renin-Angiotensin System
PubMed: 25599970
DOI: 10.1113/expphysiol.2014.079889 -
Kidney & Blood Pressure Research 2018Blood oxygen level-dependent magnetic resonance imaging (BOLD MRI) has recently been utilized as a noninvasive tool for evaluating renal oxygenation. Several methods... (Review)
Review
Blood oxygen level-dependent magnetic resonance imaging (BOLD MRI) has recently been utilized as a noninvasive tool for evaluating renal oxygenation. Several methods have been proposed for analyzing BOLD images. Regional ROI selection is the earliest and most widely used method for BOLD analysis. In the last 20 years, many investigators have used this method to evaluate cortical and medullary oxygenation in patients with ischemic nephropathy, hypertensive nephropathy, diabetic nephropathy, chronic kidney disease (CKD), acute kidney injury and renal allograft rejection. However, clinical trials of BOLD MRI using regional ROI selection revealed that it was difficult to distinguish the renal cortico-medullary zones with this method, and that it was susceptible to observer variability. To overcome these deficiencies, several new methods were proposed for analyzing BOLD images, including the compartmental approach, fractional hypoxia method, concentric objects (CO) method and twelve-layer concentric objects (TLCO) method. The compartmental approach provides an algorithm to judge whether the pixel belongs to the cortex or medulla. Fractional kidney hypoxia, measured by using BOLD MRI, was negatively correlated with renal blood flow, tissue perfusion and glomerular filtration rate (GFR) in patients with atherosclerotic renal artery stenosis. The CO method divides the renal parenchyma into six or twelve layers of thickness in each coronal slice of BOLD images and provides a R2* radial profile curve. The slope of the R2* curve associated positively with eGFR in CKD patients. Indeed, each method invariably has advantages and disadvantages, and there is generally no consensus method so far. Undoubtedly, analytic approaches for BOLD MRI with better reproducibility would assist clinicians in monitoring the degree of kidney hypoxia and thus facilitating timely reversal of tissue hypoxia.
Topics: Animals; Humans; Hypoxia; Magnetic Resonance Imaging; Oxygen; Renal Circulation; Renal Insufficiency, Chronic
PubMed: 29539614
DOI: 10.1159/000488072 -
Critical Care (London, England) Dec 2016The effects of blood transfusion on renal microcirculation during sepsis are unknown. This study aimed to investigate the effect of blood transfusion on renal...
BACKGROUND
The effects of blood transfusion on renal microcirculation during sepsis are unknown. This study aimed to investigate the effect of blood transfusion on renal microvascular oxygenation and renal function during sepsis-induced acute kidney injury.
METHODS
Twenty-seven Wistar albino rats were randomized into four groups: a sham group (n = 6), a lipopolysaccharide (LPS) group (n = 7), a LPS group that received fluid resuscitation (n = 7), and a LPS group that received blood transfusion (n = 7). The mean arterial blood pressure, renal blood flow, and renal microvascular oxygenation within the kidney cortex were recorded. Acute kidney injury was assessed using the serum creatinine levels, metabolic cost, and histopathological lesions. Nitrosative stress (expression of endothelial (eNOS) and inducible nitric oxide synthase (iNOS)) within the kidney was assessed by immunohistochemistry. Hemoglobin levels, pH, serum lactate levels, and liver enzymes were measured.
RESULTS
Fluid resuscitation and blood transfusion both significantly improved the mean arterial pressure and renal blood flow after LPS infusion. Renal microvascular oxygenation, serum creatinine levels, and tubular damage significantly improved in the LPS group that received blood transfusion compared to the group that received fluids. Moreover, the renal expression of eNOS was markedly suppressed under endotoxin challenge. Blood transfusion, but not fluid resuscitation, was able to restore the renal expression of eNOS. However, there were no significant differences in lactic acidosis or liver function between the two groups.
CONCLUSIONS
Blood transfusion significantly improved renal function in endotoxemic rats. The specific beneficial effect of blood transfusion on the kidney could have been mediated in part by the improvements in renal microvascular oxygenation and sepsis-induced endothelial dysfunction via the restoration of eNOS expression within the kidney.
Topics: Acute Kidney Injury; Animals; Blood Transfusion; Kidney; Oxygen Consumption; Random Allocation; Rats; Rats, Wistar; Renal Circulation; Sepsis
PubMed: 27993148
DOI: 10.1186/s13054-016-1581-1 -
Transplantation Jun 2017The aim of this study is to demonstrate the usefulness of adding 3-dimensional (3D) ultrasound in evaluation of renal transplant vasculature compared to 2-dimensional... (Comparative Study)
Comparative Study
BACKGROUND
The aim of this study is to demonstrate the usefulness of adding 3-dimensional (3D) ultrasound in evaluation of renal transplant vasculature compared to 2-dimensional (2D) Duplex ultrasound.
METHODS
One hundred thirteen consecutive renal transplant 2D and 3D ultrasound examinations were performed and retrospectively reviewed by 2 board-certified radiologists and a radiology resident individually; each reviewed 2D and then 3D images, including color and spectral Doppler. They recorded ability to visualize the surgical anastomosis and rated visualization on a subjective scale. Interobserver agreement was evaluated. Variant anastomosis anatomy was recorded. Tortuosity or stenosis was evaluated if localized Doppler velocity elevation was present.
RESULTS
The reviewers directly visualized the anastomosis more often with 3D ultrasound ((Equation is included in full-text article.)=97.5%) compared with 2D ((Equation is included in full-text article.)=54.5%) [difference in means (DM) = 43% (95% confidence interval (CI) = 36%-50%) (P < 0.001)]. The reviewers visualized the anastomosis more clearly with 3D ultrasound (P < 0.001) [difference in medians = 0.5, 1.0, and 1.0, (95% CI = 0.5-1.0, 0.5-1.0, and 1.0-1.5)]. Detection of variant anatomy improved with 3D ultrasound by 2 reviewers [DM = 7.1% and 8.9% (95% CI = 1%-13% and 4%-14%, respectively) (P < 0.05)]. There was high interobserver agreement [(Equation is included in full-text article.)= 95.3%, (95% CI = 91.9%-98.7%) regarding anastomosis visualization among reviewers with wide-ranging experience.
CONCLUSIONS
Direct visualization of the entire anastomosis was improved with 3D ultrasound. Three-dimensional evaluation improved detection of anatomic variants and identified tortuosity as the likely cause of borderline localized elevation in Doppler velocity. The data added by 3D ultrasound may obviate confirmatory testing with magnetic resonance angiography or computed tomographic angiography after equivocal 2D ultrasound results.
Topics: Adult; Aged; Angiography, Digital Subtraction; Blood Flow Velocity; Female; Humans; Image Interpretation, Computer-Assisted; Imaging, Three-Dimensional; Kidney; Kidney Transplantation; Male; Middle Aged; Observer Variation; Postoperative Complications; Predictive Value of Tests; Renal Artery; Renal Circulation; Renal Veins; Reproducibility of Results; Retrospective Studies; Time Factors; Treatment Outcome; Ultrasonography, Doppler, Color
PubMed: 28291767
DOI: 10.1097/TP.0000000000001206 -
American Journal of Physiology. Renal... Dec 2018Renal segmental metabolism is reflected by the complex distribution of the main energy pathways along the nephron, with fatty acid oxidation preferentially used in the... (Review)
Review
Renal segmental metabolism is reflected by the complex distribution of the main energy pathways along the nephron, with fatty acid oxidation preferentially used in the cortex area. Ischemia/reperfusion injury (IRI) is due to the restriction of renal blood flow, rapidly leading to a metabolic switch toward anaerobic conditions. Subsequent unbalance between energy demand and oxygen/nutrient delivery compromises kidney cell functions, resulting in a complex inflammatory cascade including the production of reactive oxygen species (ROS). Renal IRI especially involves lipid accumulation. Lipid peroxidation is one of the major events of ROS-associated tissue injury. Here, we briefly review the current knowledge of renal cell lipid metabolism in normal and ischemic conditions. Next, we focus on renal lipid-associated injury, with emphasis on its mechanisms and consequences during the course of IRI. Finally, we discuss preclinical observations aiming at preventing and/or attenuating lipid-associated IRI.
Topics: Acute Kidney Injury; Animals; Anti-Inflammatory Agents; Antioxidants; Humans; Iron Chelating Agents; Kidney; Lipid Metabolism; Lipid Peroxidation; Oxidative Stress; Reactive Oxygen Species; Renal Circulation; Reperfusion Injury; Signal Transduction
PubMed: 30332314
DOI: 10.1152/ajprenal.00322.2018 -
Journal of the American Heart... Jul 2020Background The sodium/glucose cotransporter 2 inhibitor empagliflozin has cardiorenal protective properties through mechanisms beyond glucose control. In this study we... (Randomized Controlled Trial)
Randomized Controlled Trial
Acute and Chronic Effects of SGLT2 Inhibitor Empagliflozin on Renal Oxygenation and Blood Pressure Control in Nondiabetic Normotensive Subjects: A Randomized, Placebo-Controlled Trial.
Background The sodium/glucose cotransporter 2 inhibitor empagliflozin has cardiorenal protective properties through mechanisms beyond glucose control. In this study we assessed whether empagliflozin modifies renal oxygenation as a possible mechanism of renal protection, and determined the metabolic, renal, and hemodynamic effects of empagliflozin in nondiabetic subjects. Methods and Results In this double-blind, randomized, placebo-controlled study, 45 healthy volunteers underwent blood and urine sampling, renal ultrasound, and blood-oxygenation-level-dependent magnetic resonance imaging before and 180 minutes after administration of 10 mg empagliflozin (n=30) or placebo (n=15). These examinations were repeated after 1 month of daily intake. Cortical and medullary renal oxygenation were not affected by the acute or chronic administration of empagliflozin, as determined by 148 renal blood-oxygenation-level-dependent magnetic resonance imaging examinations. Empagliflozin increased glucosuria (24-hour glucosuria at 1 month: +50.1±16.3 g). The acute decrease in proximal sodium reabsorption, as determined by endogenous fractional excretion of lithium (-34.6% versus placebo), was compensated at 1 month by a rise in plasma renin activity (+28.6%) and aldosterone (+55.7%). The 24-hour systolic and diastolic ambulatory blood pressures decreased significantly after 1 month of empagliflozin administration (-5.1 and -2.0 mm Hg, respectively). Serum uric acid levels decreased (-28.4%), hemoglobin increased (+1.7%), and erythropoietin remained the same. Conclusions Empagliflozin has a rapid and significant effect on tubular function, with sustained glucosuria and transient natriuresis in nondiabetic normotensive subjects. These effects favor blood pressure reduction. No acute or sustained changes were found in renal cortical or medullary tissue oxygenation. It remains to be determined whether this is the case in nondiabetic or diabetic patients with congestive heart failure or kidney disease. : URL: https://www.clinicaltrials.gov; Unique identifier: NCT03093103.
Topics: Adolescent; Adult; Benzhydryl Compounds; Biomarkers; Blood Pressure; Double-Blind Method; Female; Glucosides; Healthy Volunteers; Humans; Kidney; Male; Middle Aged; Natriuresis; Oxygen; Oxygen Consumption; Renal Circulation; Sodium-Glucose Transporter 2 Inhibitors; Switzerland; Time Factors; Young Adult
PubMed: 32567439
DOI: 10.1161/JAHA.119.016173