Albumin Clearance Research Articles

Documentation of pulmonary capillary permeability in the adult respiratory distress syndrome accompanying human sepsis.

Current evidence suggests that pulmonary edema accompanying human sepsis may result either from changes in the serum oncotic and hydrostatic pressures or an increase in the permeability of the pulmonary microvasculature. In this study, we compared the "clearance" of injected 131I-labeled human serum albumin from blood to bronchoalveolar secretions in intubated patients with pulmonary edema secondary to sepsis or myocardial infarction. A significantly increased mean +/- SE clearance of the radionuclide was seen in patients with sepsis (0.34 +/- 0.03 ml per hour) compared to those with myocardial infarction (0.043 +/- 0.008 ml per hour) (P less than 0.001), although both groups had similar degrees of edema on chest radiographs. Because the patients with sepsis had no severe decrease in serum oncotic pressure (18.4 +/- 5.0 mm Hg) or evidence of left heart failure, as determined by the pulmonary wedge pressure (11.0 +/- 6.8 mm Hg), we concluded that the genesis of the pulmonary edema in sepsis was due to an increase in pulmonary microvascular permeability, as measured by the increased clearance of 131I-labeled human serum albumin.

Prevalence of sleep disorders among ESRD patients

Sleep disorders are common among the patients undergoing dialysis in end stage renal disease (ESRD). Although variable, their prevalence has been reported to be higher when compared to the general population. The most frequently reported complaints are insomnia, restless leg syndrome (RLS), sleep-disordered breathing and excessive daytime sleepiness (EDS). The aim of this study was to assess the prevalence of sleep disorders in end stage renal disease patients on regular hemodialysis (group I with 30 patients) and CKD patients (group II with 30 patients) in comparison to 30 normal population (control group). In addition to laboratory investigations which included creatinine clearance using Cockroft and Gault formula, hemoglobin level (Hb), blood urea, serum creatinine, serum albumin, serum calcium and phosphorus and lipid profile, all subjects underwent one night of laboratory-based polysomnography (PSG) consisting of a standard montage of electroencephalography (EEG) (C3/A1 and O2/C3 or O1/C4), monopolar left and right electrooculography (EOG) referenced to the opposite mastoid, surface mentalis electromyography (EMG), respiratory airflow (measured by thermistor) and effort (piezoelectric sensors), electrocardiography (ECG), anterior tibialis EMG and pulse oximetry. For hemodialysis subjects, this study was performed on a night immediately following hemodialysis treatment. The results showed that patients on hemodialysis have sleep disorders, and that sleep disorders are common in group I and II than control group. The percentage of sleep disorders in hemodialysis patients were as follows: insomnia (69%), followed by obstructive sleep apnea syndrome OSAS (24%), RLS and periodic limb movement PLM (18%), nightmares (13%), EDS (12%), sleepwalking (2%), possible rapid eye movement behavior disorders RED (2%), possible narcolepsy (1.4%). While the percentage of sleep disorders in CKD patients were as follows: insomnia (54%), followed by RLS (19%), PLM (12%), OSAS (16%), nightmares (15%), EDS (15%), sleepwalking (4%), possible RBD (3%), possible narcolepsy (1%). There was inverse correlation between sleep disorders and Hb, albumin and creatinine clearance; also there was positive correlation between sleep disorder and phosphorus. We concluded that the sleep disorders are common in CKD patients either on conservative management or on regular hemodialysis. Treatment of anemia, hyperphosphatemia and hypoalbuminemia may improve sleep disorders among those patients.

Study of renal and hepatic toxicity in rats supplemented with creatine

To evaluate the renal and hepatic function, through biochemical analysis after 14 days of creatine supplementation in physically inactive rats. Twenty four male, adult, Wistar rats were used which were kept in individual metabolic cages and were distributed into four groups, and received the following treatments by gavage:1) CONTROL: distilled water; 2)Creatine 0.5g/Kg/day; 3) Creatine 1g/Kg/day; 4) Creatine 2g/Kg/day. Their urinary outputs as well as food and water intake were daily measured. At the end of the experiment, the animals were euthanized and serum samples were stored for biochemical analysis. Creatine supplementation at the doses given produced no significant changes in plasma levels of aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase, total protein, albumin, total cholesterol, HDL cholesterol, LDL cholesterol, VLDL cholesterol, triglycerides, glucose, creatinine, urea, and creatinine clearance, compared to control group (p> 0.05) Similarly, water and food intake, as well as urinary output, did not show significant changes among the four groups studied. At the doses used, oral creatine supplementation did not result in renal and/or hepatic toxicity.

A Multidrug, Antiproteinuric Approach to Alport Syndrome: A Ten-Year Cohort Study

Background/Aims: Combined ACE inhibitor, angiotensin-receptor-blocker, non-dihydropyridine calcium-channel-blocker, and statin therapy (Remission Clinic) reduced proteinuria and halted progression in non-diabetic nephropathies, but their efficacy in Alport syndrome (AS) nephropathy is unknown. Methods: From February 2004 to September 2007, we included nine albuminuric AS adults with creatinine clearance >20 ml/min/1.73 m² in a single-center, open-label, prospective, off-on-off academic study. After the 1-month wash-out from RAS inhibition (Run-in), patients entered the 4-month, add-on, treatment period with benazepril (10-20 mg/day), valsartan (80-160 mg/day), diltiazem (60-120 mg/day), and fluvastatin (40-80 mg/day) followed by the 1-month wash-out (Recovery). The primary outcome was albuminuria at month 4. After recovery, patients were kept on the Remission Clinic protocol and followed until July 2014 (Extension). Results: The median (IQR) albuminuria progressively declined from 657.7 (292.7-1,089.6) μg/min at baseline to 71.4 (21.7-504.9) μg/min at treatment end (p = 0.009) and raised to 404.3 (167.9-446.8) μg/min after recovery. Albumin and IgG fractional clearances significantly (p ≤ 0.005) decreased from 66.9 (53.6-80.8) to 9.4 (4.6-26.0) and from 5.1 (3.0-8.4) to 1.1 (0.6-3.2), and then recovered toward baseline. Blood pressure and lipids significantly decreased on treatment, without changes in inulin-measured GFR or para-aminohippuric-measured RPF. After recovery, one patient refused to enter the extension, one with severe renal insufficiency at baseline reached ESRD, and seven retained normal serum creatinine until the end of the study. At the final visit, three were microalbuminuric and one was normoalbuminuric. Treatment was well tolerated. Conclusion: The Remission Clinic approach safely ameliorated albuminuria, blood pressure, lipids, and glomerular selectivity in AS patients and halted long-term progression in those without renal insufficiency to start with.

Association of ABCG2 polymorphism with clinical efficacy of imatinib in patients with gastrointestinal stromal tumor.

Imatinib is a substrate of drug transporters and metabolizing enzymes, including members of the cytochrome P450 (CYP) system. Differences in imatinib pharmacokinetics among individuals might be influenced by genetic polymorphisms and be associated with variable clinical imatinib efficacy. This study sought to test how genetic polymorphisms can affect the clinical efficacy of imatinib and its blood levels in GIST patients. A total of 209 GIST patients who had received imatinib 400 mg daily were genotyped for six single-nucleotide polymorphisms in three genes (CYP3A5 6986A>G; ABCB1 1236C>T, 2677G>A/T, and 3435C>T; and ABCG2 34G>A and 421C>A) via blood samples. Progression-free survival (PFS) and imatinib plasma trough levels were evaluated and compared according to genotypes. With a median follow-up of 39.6 months (range 16.7-97.5 months), the estimated 5-year PFS rate was 67.5 % (95 % CI 59.9-75.1). Among the CYP3A5, ABCB1, and ABCG2 genotypes, ABCG2 421C>A was associated with PFS. The 5-year PFS rate in patients with the AA variant of ABCG2 421C>A (92.3 %; 95 % CI 77.8-100.0) was significantly superior to that of patients with CC/CA genotypes (65.0 %; 95 % CI 56.9-73.1; p = 0.047). For the imatinib trough levels, there were no statistically significant differences when comparing polymorphisms among all genotypes, even after adjusting for clinical factors, including sex, age, body surface area, hemoglobin, albumin, and creatinine clearance. The ABCG2 421C>A genetic variation could influence clinical efficacy in terms of PFS in patients with advanced GIST undergoing imatinib therapy.

Flavonoid rich fraction of Punica granatum improves early diabetic nephropathy by ameliorating proteinuria and disturbed glucose homeostasis in experimental animals

Context: Different parts of Punica granatum Linn. (Punicaceae) are traditionally used as renal protective agents in the Indian system of medicine. However, there is paucity of information regarding its role in diabetic nephropathy.Objective: The present study investigates the nephroprotective potential of flavonoid-rich fraction of P. granatum leaves in streptozotocin (STZ)-induced early diabetic nephropathy in experimental animals.Materials and methods: Experimental diabetic nephropathy was induced in Wistar rats by single intraperitonial injection of STZ (65 mg/kg) dissolved in ice cold citrophosphate buffer (pH 4.3). After induction rats were divided into five groups (6 normal; 24 diabetic) and administered with glibenclamide (5 mg/kg) and three dose levels of flavonoid-rich fraction of P. granatum leaves (PGFF), i.e. 50, 100, and 200 mg/kg body weight/day for 28 d. Fasting blood glucose, lipid profile, serum albumin, serum total protein, serum creatinine, blood urea nitrogen (BUN) glycosylated hemoglobin, and biomarkers of kidney oxidative stress were assessed at the end of the treatment period. Urine was analyzed for the measurement of total protein, albumin, and creatinine clearance. Kidney sections were subjected to histopathological study.Results: Daily oral administration of variable dose levels of PGFF for 28 d normalized various biochemical, metabolic, and histopathological changes in the diabetic rats. PGFF significantly (p < 0.01 and p < 0.05) improved the glycemic status and renal function in diabetic rats as compared with diabetic control rats.Discussion and conclusion: The results of our study thus prove the protective effect of PGFF in early diabetic nephropathy by ameliorating proteinuria and disturbed glucose homeostasis in experimental animals.

Role of transient receptor potential vanilloid type 1 and C-C chemokine receptor 2 in renal injury induced by salt-sensitive hype

To determine the effects of transient receptor potential vanilloid type 1 (TRPV1) channel ablation and a chemokine receptor 2 (CCR2) antagonist on salt-sensitive hypertension-induced renal injury. Wild-type (WT) and TRPV1-null mutant (TRPV1(-/-)) mice were subjected to uninephrectomy and deoxycorticosterone acetate (DOCA)-salt treatment for 4 weeks with or without a CCR2 antagonist, RS504393 (n=8 for all the 4 groups). Sham WT and TRPV1(-/-) mice (both n=7) underwent uninephrectomy without receiving DOCA and saline. Systolic blood pressure, urinary excretion of albumin, 8-isoprostane and creatinine clearance for 24 hours were assayed during the experimental period and at the end of the 4-week treatment. The morphological analysis was performed in renal histological sections, including glomerulosclerosis, tubulointerstitial injury, and monocyte/macrophage infiltration. Compared to the corresponding control mice, DOCA-salt treatment in both WT and TRPV1(-/-) mice led to increased systolic blood pressure (SBP), enhanced urinary excretion of albumin and 8-isoprostane, decreased creatinine clearance, increased glomerulosclerosis and tubulointerstitial injury associated with enhanced monocyte/macrophage infiltration (all P<0.05), all of which were much more severe in TRPV1(-/-) mice compared to WT mice with the exception of blood pressure (all P<0.05). RS5043943 attenuated DOCA-salt-induced changes in renal function and morphology in WT and TRPV1(-/-) mice (all P<0.05). There was no difference in blood pressure among DOCA-salt WT and TRPV1(-/-) mice with or without RS505393 with the exception of sham WT and TRPV1(-/-) mice (all P>0.05). CCR2 antagonist inhibits DOCA-salt-induced renal injury and monocyte/macrophage infiltration in WT and TRPV1(-/-) mice with the greater in the latter strain. Activation of TRPV1 attenuates salt-sensitive hypertension-induced renal injury possibly via inhibition of CCR2-induced monocyte/macrophage infiltration.

Visual acuity and increased mortality: the role of allostatic load and functional status.

Poor vision may detrimentally impact functional status and affect allostatic load (AL), a measure of cumulative physiological wear and tear on the body's regulatory systems. We examined the direct effects of visual acuity (VA) on mortality and its indirect effect on mortality through its impact on functional status and AL in older adults. Data from 4981 participants (age ≥ 60 years) from the 1999-2004 National Health and Nutrition Examination Survey (NHANES) with mortality linkage through 2006 were analyzed. Functional status was assessed by activities of daily living (ADL) and instrumental activities of daily living (IADL). The AL index was composed of 10 biomarkers: systolic and diastolic blood pressures, body mass index (BMI), glycosylated hemoglobin, total cholesterol, triglycerides, albumin, C-reactive protein, homocysteine, and creatinine clearance. Visual acuity was categorized as no (20/20-20/25), mild (20/30-20/40), moderate (20/50-20/80), or severe (≥20/200) visual impairment. Structural equation modeling using three mediating variables representing ADL, IADL, and AL examined the effects of VA on all-cause and cardiovascular disease (CVD)-related mortality. Adjusting for all covariates, a one-unit change in VA category increased mortality risk (hazard ratio [HR] = 1.17; 95% confidence interval [CI] 1.05, 1.32); IADL and AL predicted mortality (HR = 1.15; CI 1.10, 1.20 and HR = 1.13; CI 1.06, 1.20, respectively). Activities of daily living did not predict mortality (HR = 0.98; CI 0.91, 1.05). Worse VA was associated with increased AL (β = 0.11; P = 0.013) and worse IADL (β = 1.06; P < 0.001). Worse VA increased mortality risk indirectly through AL (HR = 1.01; CI 1.00, 1.03) and IADL (HR = 1.16; CI 1.09, 1.23). The total effect of VA on mortality including through IADL and AL was HR = 1.38 (CI 1.23, 1.54). Similar but slightly stronger patterns of association were found when examining CVD-related mortality, but not cancer-related mortality. Allostatic load and particularly IADL may function as mediators between VA impairment and mortality. Older adults with VA impairment could potentially benefit from interventions designed to prevent IADL functional status decline to reduce the risk of mortality.

THU0055 Elevated Cfdna is Associated with Active Lupus Nephritis and May Mainly Derive from Netosis in Systemic Lupus Erythematosus

BackgroundAbnormal formation and insufficient clearance of neutrophil extracellular traps (NETs) has been involved in lupus nephritis (LN). The residual NETs is one potential source of circulating cell-free DNA (cfDNA). However,...

A flavonoid fraction purified from Rutaceae aurantiae (DaflonR) inhibiting AGE formation, reduces urinary albumin clearance and corrects hypoalbuminemia in normotensive and hypertensive diabetic rats

AimAdvanced glycation endproducts (AGEs) have been shown to contribute to alteration of glomerular permselectivity to proteins in diabetes. Oxidative stress is required for AGE formation. Therefore we studied the effect of an antioxidant micronized purified flavonoid fraction (MPFF, DaflonR 500mg), on urinary albumin clearance in diabetic rats. MethodsHyperglycaemia was induced by streptozotocin 55mg/kg IM at days 0 and 7 in normotensive Wistar rats (NWR, diabetes duration 5 months) or hypertensive Wistar Kyoto rats (SHR, diabetes duration 2 months). MPFF was administered at 300mg/kg/day, from day −2 until sacrifice. ResultsAfter 5 months of diabetes in NWR, MPFF reduced albumin clearance from 729±92 to 392±60nl/min/kg, p<0.01, and restored albuminemia from 20.4±0.9 to 24.0±1g/l, p<0.05; albumin fractional clearance was significantly diminished in the flavonoid-treated diabetic rats (0.360±0.037‰ versus 1.335±0.430‰ in the diabetic controls, p<0.001); MPFF did not significantly modify blood glucose and plasma fructosamine levels. After 2 months of diabetes in SHR, MPFF reduced albumin clearance from 243±121 to 101±47nl/min/kg, p<0.05, and restored albuminemia from 21.1±1.6 to 26.7±2.2g/l (p<0.05); MPFF also decreased plasma fluorescence characteristic of AGEs (p<0.02). Besides hesperetin, a main metabolite of MPFF recovered in plasma, inhibited in vitro the formation of the crosslinking AGE pentosidine in collagen incubated with high glucose (p<0.001). ConclusionOur results confirm the role of glycoxidative stress in diabetic nephropathy. MPFF might be useful as complementary treatment for preventing diabetic microangiopathy.

Glycosaminoglycan Regulation by VEGFA and VEGFC of the Glomerular Microvascular Endothelial Cell Glycocalyx in Vitro

Damage to endothelial glycocalyx impairs vascular barrier function and may contribute to progression of chronic vascular disease. An early indicator is microalbuminuria resulting from glomerular filtration barrier damage. We investigated the contributions of hyaluronic acid (HA) and chondroitin sulfate (CS) to glomerular microvascular endothelial cell (GEnC) glycocalyx and examined whether these are modified by vascular endothelial growth factors A and C (VEGFA and VEGFC). HA and CS were imaged on GEnCs and their resynthesis was examined. The effect of HA and CS on transendothelial electrical resistance (TEER) and labeled albumin flux across monolayers was assessed. Effects of VEGFA and VEGFC on production and charge characteristics of glycosaminoglycan (GAG) were examined via metabolic labeling and liquid chromatography. GAG shedding was quantified using Alcian Blue. NDST2 expression was examined using real-time PCR. GEnCs expressed HA and CS in the glycocalyx. CS contributed to the barrier to both ion (TEER) and protein flux across the monolayer; HA had only a limited effect. VEGFC promoted HA synthesis and increased the charge density of synthesized GAGs. In contrast, VEGFA induced shedding of charged GAGs. CS plays a role in restriction of macromolecular flux across GEnC monolayers, and VEGFA and VEGFC differentially regulate synthesis, charge, and shedding of GAGs in GEnCs. These observations have important implications for endothelial barrier regulation in glomerular and other microvascular beds.

Dual activation of p38MAPK and SFK pathways is required to induce endothelial permeability

We previously showed that activation of endogenous Src family kinases (SFK) by expression of a dominant negative form of Csk (DN‐Csk) is not sufficient to induce changes in endothelial monolayer permeability, but allows low doses of TNF to increase endothelial permeability. This increase induced by joint SFK activation and TNF treatment is attenuated by addition of p38 inhibitors. Thus, we hypothesized that p38MAPK activation may induce an increase in permeability of ECs already primed by activation of SFKs. To test this, we constructed a lentiviral vector to express a flag tagged constitutively active form of MKK6 under the control of a tetracycline‐regulated promoter (iMKK6E). Addition of doxycyclin (dox) to infected cells induced a dose‐dependent increase in MKK6E expression resulting in the phosphorylation and nuclear translocation of p38 as well as HSP27 phosphorylation. This treatment did not induce any change in permeability. In contrast, MKK6E expression resulted in a large drop in TEER and an increase in albumin clearance in cells with SFK activation. This was accompanied by the formation of large gaps in the monolayer but no change in actin fibers. Our results support a model in which dual activation of SFKs and p38 are required for the induction of endothelial permeability. This model could explain the tight spatio‐temporal response to inflammatory mediators during an inflammatory response.

Vibration Enhances Clearance of Solutes With Varying Molecular Weights During In Vitro Hemodialysis

This proof of concept pilot study was performed to determine whether vibration can increase solute clearance when applied to an in vitro dialysis model. Urea, creatinine, gentamicin, and vancomycin transmembrane clearances were calculated at a blood flow rate of 200 ml/min, dialysate flow rates of 2 and 8 L/hr, and no concurrent ultrafiltration at various vibration intensities. Dialyzer integrity was determined by measuring transmembrane pressure, filter drop pressure, and albumin clearance, and by visually inspecting the dialysate. Comparing the highest vibration modality with no vibration, the median percentage increase in urea, creatinine, gentamicin, and vancomycin clearance was 18% (all p < 0.005). The transmembrane clearance of albumin was negligible for all experiments. When measuring transmembrane pressure and filter drop pressure, no significant differences were found between nonvibration and vibration dialysis. The addition of vibration during dialysis increased transmembrane clearance for solutes with molecular weights of 60-1450 Daltons.

Treatment with oral paricalcitol in daily clinical practice for patients with chronic kidney disease stage 3-4: a preliminary study.

BackgroundActive vitamin D is an effective treatment for secondary hyperparathyroidism (SHPT) in chronic kidney disease (CKD) patients often complicated by hypercalcaemia and hyperphosphataemia. Treatment with paricalcitol, a selective vitamin D receptor activator, has shown benefits by adequately reducing parathyroid hormone (PTH) levels with minimal changes in serum calcium (Ca) and phosphorus (P). The purpose of this study is to present data on the use of oral paricalcitol in real-life clinical practice in patients with CKD stage 3–4 and SHPT.MethodsWe studied 43 patients, M/F: 25/18, median age: 74 years (47–87), CKD stage 3/4: 16/27, with SHPT, who were prescribed oral paricalcitol at recommended doses for 6 months. Monthly measurements of serum intact PTH (iPTH), Ca, P, alkaline phosphatase (ALP), haemoglobin, albumin (ALB), lipid profile, proteinuria and 24-h urine creatinine clearance were performed 3 months before and 6 months after treatment initiation.ResultsParicalcitol induced a significant, early and sustained, through the end of follow-up period, decrease in iPTH and ALP levels and an increase in serum ALB. No significant increase in Ca and P levels as well as in Ca × P product was observed during the study period. No significant changes were found in protein excretion, kidney function and the other measured parameters between baseline and last evaluation. Paricalcitol final median dose was 5 μg/week ranging between 3 and 7 μg/week.ConclusionsIn the context of real-life clinical practice, oral paricalcitol for 6 months is an effective, well-tolerated treatment of SHPT in CKD stage 3–4 with minimal effects on calcium and phosphorus metabolism.

Enhancing Effect of Poly(amino acid)s on Albumin Uptake in Human Lung Epithelial A549 Cells

The clearance of albumin from the alveolar space is a critical process in the recovery from edema. In this study, we investigated the effect of poly(amino acid)s such as poly-l-ornithine (PLO) on albumin uptake in the cultured lung epithelial cell line A549. FITC-albumin uptake as well as cell surface binding was markedly stimulated by co-incubation with PLO, and there was a good correlation between them. After being taken up by A549 cells, FITC-albumin was predominantly targeted to lysosomes. Interestingly, pretreatment of A549 cells with PLO further stimulated FITC-albumin uptake, even in the absence of PLO in the uptake buffer. FITC-albumin uptake in the presence of PLO was inhibited by a metabolic inhibitor, clathrin-mediated endocytosis inhibitors, and a macropinocytosis inhibitor, indicating the involvement of clathrin-mediated endocytosis and/or macropinocytosis. The effect of PLO on FITC-albumin clearance was also examined in an in vivo pulmonary administration method in rats, and co-administration of PLO enhanced fluorescence elimination from the lungs. These findings suggest that pulmonary administration of poly(amino acid)s such as PLO is a possible strategy for enhancing albumin clearance from the alveolar space, and thereby facilitating the recovery from pulmonary edema.

Risk factors associated with brachial–ankle pulse wave velocity among peritoneal dialysis patients in Macao

BackgroundCardiovascular disease is the leading cause of mortality among peritoneal dialysis (PD) patients in Macao. Increased arterial stiffness determined by pulse wave velocity (PWV) has been established as an independent predictor of cardiovascular mortality in end-stage renal disease patients. The present study aims to investigate the relationship between arterial stiffness and its associated risk factors in chronic PD patients.MethodsA total of 96 chronic PD patients (48 males/48 females) were included in the cross-sectional study. Arterial stiffness was assessed by brachial-ankle PWV (baPWV). Patients were divided into two subgroups according to mean baPWV value. On enrollment, clinical characteristics and biochemical parameters were collected.ResultsCompared with low baPWV group patients, high baPWV group patients were significant older (p<0.001) and more likely to have a high proportion of female gender (p=0.004) as well as previous CVD history (p=0.008). Serum albumin, pre-albumin levels and residual renal creatinine clearance (CCr) were significantly lower but the serum ferritin level was significantly higher in high baPWV group patients than in low baPWV group patients (all p<0.01). BaPWV was positively associated with age (r=0.534, p<0.001), Charlson comorbidity index (r=0.350, p<0.001) and serum ferritin level (r=0.340, p=0.001). Meanwhile, baPWV negatively correlated with serum albumin (r=−0.479, p<0.001), pre-albumin levels (r=−0.320, p=0.003) and residual renal CCr (r=−0.177, p=0.048). Age-adjusted partial correlation test found a significant correlation between baPWV and CRP (r=0.462, p<0.001). Multivariate regression analysis showed that baPWV was independently associated with age (p<0.001), serum albumin level (p=0.015), CRP (p=0.019) and residual renal CCr (p=0.045).ConclusionArterial stiffness, assessed by baPWV, had an independent correlation with age, serum albumin level, CRP level and residual renal CCr among PD patients in Macao.

Megalin mediates transepithelial albumin clearance from the alveolar space of intact rabbit lungs

The alveolo-capillary barrier is effectively impermeable to large solutes such as proteins. A hallmark of acute lung injury/acute respiratory distress syndrome is the accumulation of protein-rich oedema fluid in the distal airspaces. Excess protein must be cleared from the alveolar space for recovery; however, the mechanisms of protein clearance remain incompletely understood. In intact rabbit lungs 29.8 ± 2.2% of the radio-labelled alveolar albumin was transported to the vascular compartment at 37°C within 120 min, as assessed by real-time measurement of 125I-albumin clearance from the alveolar space. At 4°C or 22°C significantly lower albumin clearance (3.7 ± 0.4 or 16.2 ± 1.1%, respectively) was observed. Deposition of a 1000-fold molar excess of unlabelled albumin into the alveolar space or inhibition of cytoskeletal rearrangement or clathrin-dependent endocytosis largely inhibited the transport of 125I-albumin to the vasculature, while administration of unlabelled albumin to the vascular space had no effect on albumin clearance. Furthermore, albumin uptake capacity was measured as about 0.37 mg ml−1 in cultured rat lung epithelial monolayers, further highlighting the (patho)physiological relevance of active alveolar epithelial protein transport. Moreover, gene silencing and pharmacological inhibition of the multi-ligand receptor megalin resulted in significantly decreased albumin binding and uptake in monolayers of primary alveolar type II and type I-like and cultured lung epithelial cells. Our data indicate that clearance of albumin from the distal air spaces is facilitated by an active, high-capacity, megalin-mediated transport process across the alveolar epithelium. Further understanding of this mechanism is of clinical importance, since an inability to clear excess protein from the alveolar space is associated with poor outcome in patients with acute lung injury/acute respiratory distress syndrome.

Microvascular permeability in the absence of Epac1 activity

Epac1 is a cAMP binding protein which through intrinsic guanine nucleotide exchange factor activity couples cAMP production to activation of Rap. Epac1 is abundant in blood vessel endothelium, and may contribute in the cAMP mediated attenuation of inflammatory leakage by stabilizing the endothelial barrier. To establish how basal vascular permeability is affected in the absence of Epac1 in vivo we measured blood‐to‐tissue albumin clearance and plasma volumes with a dual‐label isotope technique in isofluorane anesthetized Epac1 knockout (KO) and wt mice. Albumin permeability, calculated as the ratio of albumin clearance to local vascular volume, was significantly increased in back skin, quadriceps muscle, inguinal fat and brown fat of Epac1 KO compared to wt mice. Furthermore, there was a significant increase in water content in inguinal fat of Epac1 KO mice and with a similar tendency observed in back skin. We conclude that intact signaling through Epac1 may be of importance to maintain the basal endothelial barrier integrity in vivo and thus prevent excessive protein leakage into the interstitium of skin, muscle and fat under steady‐state conditions.The work was supported by The Research Council of Norway and The Western Norway Health Authority. The following have contributed to produce and characterize the Epac1 KO mouse: C. Krakstad, K. Kristiansen, and L. Madsen.

Experimentally induced puromycine aminonucleoside nephrosis (PAN) in rats: evaluation of angiogenic protein platelet-derived endothelial cell growth factor (PD-ECGF) expression in glomeruli.

BackgroundIn experimentally induced puromycine aminonucleoside nephrosis (PAN) animal models, nephrotic syndrome with minimal change disease and focal and segmental sclerosis-like nephritis similar to that in human is demonstrated; however, the real mechanism of PAN is not yet elucidated. Platelet derived endothelial cell growth factor (PD-ECGF), an endothelial mitogen protein, is believed to take part in microvessel formation and in stimulation of angiogenesis and its expression has not been totally demonstrated in PAN rats yet. In this study, we aimed to examine PD-ECGF expression in acute and chronic PAN induced in rats and find out the association between its expression and the stages of angiogenesis in kidney.MethodsFor the experiment, twenty-four Male Wistar Albino rats were used and divided into four groups; control group (n = 6), pre-proteinuria group (n = 6), acute group (n = 6) and chronic group (n = 6). We compared statistically all data by One-way ANOVA Test followed by Dunn Multiple Comparison Test.ResultsProteinurea levels in control and pre-proteinuria groups were not statistically different; however, it was remarkably higher in the acute nephrosis group and significantly greater in the chronic nephrosis group than control group (p < 0.0025). In pre-proteinuria group, the serum albumin and creatinine clearances also did not significantly differ from the control group. On the other hand, in the acute and chronic nephrosis groups, serum albumin and creatinine clearances progressively decreased (p < 0.05). In our immunohistochemical studies, we showed elevated PD-ECGF expression in glomeruli of acute and chronic PAN rats. Microscopic and ultrastructural appearances of the glomeruli of acute and chronic PAN showed various sequential steps of angiogenesis, macrophages and immature capillaries with primitive lumens and apoptotic endothelial cells in the increased mesangial matrix.ConclusionsIt is reported that acute and chronic PAN progressively increase PD-ECGF expression and following induction of angiogenesis in the affected glomeruli.

Phosphodiesterase 4 inhibition attenuates plasma volume loss and transvascular exchange in volume‐expanded mice

We tested the hypothesis that inhibition of phosphodiesterase 4 (PDE4) with rolipram to increase vascular endothelial cAMP and stabilize the endothelial barrier would attenuate the action of endogenous atrial natriuretic peptide (ANP) to increase vascular permeability to the plasma protein albumin after an acute plasma volume expansion. After rolipram pretreatment (8 mg (kg body wt)(-1), intraperitoneal, 30 min) more than 95% of the peak increase in plasma volume after volume expansion (4.5% bovine serum albumin, 114 μl (g body wt)(-1) h(-1), 15 min) remained in the vascular space 75 min after the end of infusion, whereas only 67% of the fluid was retained in volume-expanded animals with no rolipram pretreatment. Rolipram significantly decreased 30 min fluorescently labelled albumin clearance (μl (g dry wt)(-1)) relative to untreated volume-expanded controls in skin (e.g. back, 10.4 ± 1.6 vs. 19.5 ± 3.6, P = 0.04), muscle (e.g. hamstring, 15.0 ± 1.9 vs. 20.8 ± 1.4, P = 0.04) and in colon, caecum, and rectum (average reduction close to 50%). The mass of muscle and skin tissue accounted for 70% of volume-expansion-dependent albumin shifts from plasma to interstitium. The results are consistent with observations that the PDE4 inhibitor rolipram attenuates ANP-induced increases in vascular permeability after infusion of exogenous ANP and observations of elevated central venous pressure after a similar volume expansion in mice with selective deletion of the endothelial ANP receptor. These observations may form the basis for new strategies to retain intravenous fluid containing macromolecules.