Glomerular Markers Research Articles

Urinary protein excretion profile: A contribution for subclinical renal damage identification among environmental heavy metals exposure in Southeast Brazil

In Southeast Brazil. Ribeira Valley region has been a major public health concern due to the environmental heavy metals contamination indexes of vegetation, rocks and aquifers. caused by local mining in the past. Human contamination by low levels of heavy metals doesn't cause acute intoxication but in chronic exposure. renal damage may occur with progressive tubulointerstitial changes evolving to glomerular lesion. In this study we investigated the relationship between the profile of urinary excreted proteins (glomerular or tubular origin) of arsenic and mercury and blood lead concentration in children and adults from highly exposed regions of the Ribeira Valley. The subjects were classified as GROUP 1 (G1; higher environmental risk, n=333) and GROUP 2 (G2; lower risk of contamination. n=104) In order to determine the urinary excretion of total protein, albumin (MA. glomerular marker) and alpha 1 microglobulin (A1M, tubular marker) and the blood lead concentrations, random urine and blood samples were obtained. Plasmatic lead levels were assessed by atomic absorption spectrometry with graphite furnace. Total protein concentration (PROT) was assessed on a biochemical analyzer (pyrogallol red method). MA and AIM were determined by nephelometric method. Group 1 showed a higher frequency of altered urinary excretion of PROT (G1=34%; G2=1.0%), MA (G1=9.0%; G2=51%) and AIM (G1=7.5%; G2=3.8%), without significant differences between both groups. Elevated arsenic levels were more prevalent among subjects from Group 1 (28.8%) and demonstrated a significant correlation with abnormal urinary excretion of albumin and alpha-1-micrglobulin (p -0.019). Lead and mercury levels showed no difference among the groups and no correlation with MA and/or Al M. Our data suggests that abnormal urinary protein excretion is relatively frequent in this population independently of the plasmatic or urinary heavy metal levels. The early detection of possible renal damage become necessary for effective measures can be taken to prevent clinical nephropothies.

Cytoskeletal protein expression and regenerative markers in schistosomal nephropathy.

Progression of renal diseases is related to the abnormal regulation of cellular and extracellular matrix turnover. Other factors in addition to schistosomal antigens may be relevant to the progression of schistosomal nephropathy (SN). The validity of markers of fibroblastic differentiation, alpha smooth muscle actin (alphaSMA), and vimentin, as well as the regenerative activity (PCNA/apoptosis index) in determination of progression of SN in comparison to other forms of non-schistosomal nephropathy (non-SN) is investigated. Three groups were included; group I pure SN (n=16), group II a diverse group of non-schistosomal patients with comparable pathologic changes on renal biopsy (n=40) and a control group (n=5). Immunohistochemical staining of myofibroblasts (alphaSMA and vimentin) and proliferating cells (PCNA) and histomorphometric analysis was done. In situ end labelling (ISEL) of DNA was used to evaluate apoptosis. No differences in the patterns of distribution of positivity of the different studied markers were observed between the different nephropathy groups. Both alphaSMA and vimentin were detected in glomerular mesangial, tubular epithelial, interstitial inflammatory fibroblast-like cells and occasionally endothelial cells. PCNA and apoptotic cells were detected in tubular epithelial and interstitial cells with paucity of positive cells in the glomerulus. Significant positive correlations were detected in group I between glomerular sclerosis and interstitial markers including interstitial alphaSMA (r=0.609, P=0.001), interstitial vimentin (r=0.812, P=0.00) and interstitial apoptosis (r=0.733, P=0.001). On the other hand, glomerulosclerosis in group II showed significant positive correlations with predominantly the glomerular markers; glomerular alphaSMA (r=0.475, P=0.002), glomerular apoptosis (r=0.684, P=0.00) and glomerular PCNA (r=0.691, P=0.00). Interstitial fibrosis correlated significantly with interstitial markers in group I including interstitial alphaSMA (r=0.837, P=0.00) interstitial vimentin (r=0.929, P=0.00), interstitial apoptosis (r=0.807, P=0.00) and interstitial PCNA (r=0.617, P=0.01), while in group II it correlated with both interstitial and glomerular markers. In addition, the tubulo-interstitial ratio was significantly higher in group I in comparison with group II (P=0.024), with no difference between groups II and III. Although SN may start as glomerulopathy associated with increased mesangial cellularity, the interstitial rather than the glomerular markers of myofibroblastic differentiation and those of cell turnover are playing a crucial role in late stages of schistosomal, but not in non-schistosomal nephropathies.

Early diagnosis of endemic nephropathy

Urinary α 1-microglobulin as a tubular marker and albumin as a glomerular marker were measured in 373 subjects living in a typical endemic village of Kaniža, Croatia, previously classified as diseased, suspect, ‘at risk’ and others according to the criteria used for the diagnosis of endemic nephropathy. Based on the excretion pattern of α 1-microglobulin and albumin and its extent, significant tubular with significant glomerular proteinuria was found in seven diseased subjects. Significant tubular proteinuria with slight glomerular proteinuria was found in one diseased subject, while another diseased subject had slight tubular with significant glomerular proteinuria. Significant tubular with significant glomerular proteinuria was found in only one suspect subject. Also, significant tubular proteinuria was established in one other subject.

Risk Assessment of Nephrotoxicity of Cadmium

Cadmium as an environmental or occupational toxin has been well studied. Exposure can fairly easily be detected by analysis of cadmium in biological material. Different routes of cadmium uptake, such as via airborne particles, cigarette smoke or contaminated food, have been identified. Urinary concentrations associated with renal effects vary, depending on urinary marker of effect, and are as low as 2 μg cadmium/g creatinine. Different segments of the nephron are affected by cadmium. Urinary enzymes and serum derived proteins, mainly low-molecular weight proteins, as well as eicosanoids or glycosaminoglycans are among the tubular or glomerular markers of effect. Predisposing factors, such as smoking, dietary habits and low body iron stores have been described. It is concluded that even for low level cadmium exposure effects can be detected with sensitive diagnostic tools.

Urinary Excretion of Thromboxane and Markers for Renal Injury in Patients Undergoing Cardiopulmonary Bypass

Urinary excretion of selected markers for renal injury, as well as urinary excretion rates of the thromboxane metabolite, 11-keto-thromboxane B2 (11k-TXB2), was studied in 36 male patients undergoing coronary bypass surgery using cardiopulmonary bypass (CPB). In all patients, excretion of both tubular (N-acetyl-beta-D-glucosaminidase [beta NAG]; alpha 1-microglobulin [alpha 1-MG]) and glomerular markers (albumin [Alb]; transferrin [Trf]; immunoglobulin G [IgG]) sharply increased on Day 1 after CPB, and they remained elevated throughout the observation period of 5 days. Urinary excretion rates of 11k-TXB2 markedly increased on Day 1 after surgery, and they rapidly decreased thereafter. In 12 of the 36 patients, a temporary increase of serum creatinine levels (> 1.30 mg/dl) was noted following surgery. A positive correlation was found between serum creatinine levels and excretion of the tubular enzyme beta NAG (r = 0.36; p < 0.05), but not between creatinine levels and alpha 1-MG or the glomerular markers. Furthermore, no correlation between urinary excretion of 11k-TXB2 and any of the urinary markers for renal injury could be detected. Our data do not strengthen the hypothesis that acute renal injury observed during CPB is related to exaggerated thromboxane biosynthesis in these patients. Monitoring of urinary markers for incipient renal damage, particularly excretion of beta NAG, might be of additional diagnostic value for detection of otherwise subclinical renal injury in patients undergoing CPB.

Quantitative assessment of urinary protein and enzyme excretion--a diagnostic programme for the detection of renal involvement in type I diabetes mellitus.

In an effort to establish a reliable programme for the clinical monitoring of renal involvement in patients with type-I diabetes mellitus, we quantified the urinary excretion of immunoglobulin G (IgG), transferrin (Tf), albumin (Alb), alpha 1-microglobulin (alpha 1MG), N-acetyl-beta-D-glucosaminidase (NAG), and total protein in 130 dipstick negative children and young adults with type-I diabetes. Eighty-five sex- and age-matched healthy persons served as a control group for the definition of the upper reference limits (95th centiles; micrograms min-1 1.73 m2): transferrin 1.4; albumin 16.6; total protein 27.1; NAG: 2.0 mU min-1 1.73 m2. Sex-related differences were detected for IgG (men: 3.8; women: 1.7) and alpha 1 MG (men: 6.0; women: 4.0 micrograms min-1 1.73 m2). The urinary excretion of IgG, Tf, alpha 1MG, NAG, and total protein was significantly higher in subjects with diabetes when compared to healthy controls (p < 0.01). Furthermore, 20 patients (15%) showed an elevated excretion of tubular markers (alpha 1MG and NAG), and 3 patients (2%) of at least two glomerular markers (Alb and/or Tf and/or IgG). Additionally, 18 individuals (14%) presented a mixed excretion pattern of both tubular and glomerular markers. These data suggest that the quantitation of both glomerular and tubular proteinuria provides a sensitive and cost-effective instrument for the non-invasive screening for renal involvement in patients with diabetes mellitus.

Beta2-microglobulinuria as an early sign of cytomegalovirus infection following renal transplantation.

The frequency of cytomegalovirus infection was studied in a prospective study of 106 kidney recipients. The detection of cytomegalovirus-immediate-early-antigen and cytomegalovirus-immunoglobulin (IgM) antibodies in serum was used as the reference method and showed that 23.6% (25/106) of all patients were infected. In addition, four urinary proteins (IgG and transferrin as glomerular markers and alpha1-microglobulin and beta2-microglobulin as tubular markers) were quantitatively measured in 24-h urine samples from all of the patients using an immunoluminometric assay (ILMA). In all cytomegalovirus infection cases a pronounced but isolated increase of urinary beta2-microglobulin excretion was observed. In 20 of 25 infected patients, the beta2-microglobulinuria occurred 1-21 days (median 5.0) earlier than the appearance of the cytomegalovirus-immediate-early-antigen in blood. Thus, it can be seen that the quantitative measurement of beta2-microglobulin in urine is useful for the early detection of cytomegalovirus infection following renal transplantation.

Unchanged extraction of atrial natriuretic factor across the chronic ischemic human kidney

The extractions of atrial natriuretic factor (EANF) and the glomerular filtration marker 51Cr-ethylenediamine tetraacetic acid (EEDTA) were determined before and after intravenous injection of furosemide across each of the two kidneys during renal vein catheterization in hypertensive patients with unilateral or bilateral renovascular disease. Before administration of furosemide, EANF was approximately 55% across both the more and the less affected kidney while EEDTA was significantly decreased across the more affected kidney. Significant lateralization of renin secretion to the more affected kidney was found, demonstrating an enhanced ipsilateral formation of renin. Administration of furosemide caused a significant decrease in EEDTA across the less affected kidney while the ipsilateral EANF did not change. Furosemide caused no change in EEDTA or EANF across the more affected kidney. No significant correlations were found between EANF and EEDTA. These results demonstrate that the extraction of ANF is unchanged across the chronic ischemic human kidney. Furthermore, in the single kidney, changes in EEDTA, as induced by furosemide, are not related to changes in ipsilateral EANF. Since the relation between simultaneously determined single kidney extractions of ANF and 51Cr-EDTA reflects the relation between the single kidney clearance of ANF and the ipsilateral glomerular filtration rate, our data indicate a dissociation between changes in the single kidney glomerular filtration rate and the ipsilateral total renal clearance of ANF.

Measurement of glomerular filtration rate in conscious unrestrained rats with inulin infused by implanted osmotic pumps.

A method is described for determining glomerular filtration rate (GFR) in conscious unrestrained rats without extracellular volume expansion. The glomerular marker used was 14C-labeled inulin infused in the minimal fluid volume of 1 microliter/h by intraperitoneally implanted osmotic minipumps. The workability, reproducibility, and precision of the technique was evaluated in sham-operated (sham) and uninephrectomized (UNI-NX) rats for 6 days. In six sham-operated rats the clearance of [14C]-inulin calculated from the plasma value obtained in a blood sample taken at 10 A.M. before food consumption was (means +/- SE): day 1 after pump implantation: 1.38 +/- 0.05; day 2: 1.27 +/- 0.05; day 3: 1.46 +/- 0.16; day 4: 1.45 +/- 0.15; day 5: 1.33 +/- 0.08; day 6: 1.38 +/- 0.11 ml/min. In six UNI-NX rats the corresponding values were: day 1: 0.88 +/- 0.04; day 2: 0.79 +/- 0.05; day 3: 0.91 +/- 0.03; day 4: 0.91 +/- 0.03; day 5: 0.83 +/- 0.06; day 6: 0.87 +/- 0.05 ml/min. When determined on day 2, 3, or 6 at 6 P.M., i.e., at the end of the food consumption period, [14C]inulin clearance was increased in all animals compared with the value determined at 10 A.M. in the fasted state. The use of implanted osmotic minipumps for delivering a glomerular marker such as [14C]inulin allows the determination of GFR in conscious unrestrained rats with normal fluid balance conditions. This method appears to be particularly appropriate for studying the influence of the intake and composition of food on GFR in physiological conditions.

Vitamin B12 uptake in dog kidney: its use as an extracellular reference marker

The renal handling of [3H]cyanocobalamin has been investigated in dogs in vivo using the pulse injection multiple-indicator dilution technique. Simultaneous renal vein and urine outflow curves were obtained for [3H]cyanocobalamin relative to T-1824-albumin (plasma reference) and creatinine (extracellular reference). The renal vein recovery of [3H]cyanocobalamin relative to creatinine was significantly less than unity and increased with increasing intraarterial dose. This indicates a saturable postglomerular uptake mechanism. The urine recovery of [3H]cyanocobalamin relative to simultaneously filtered creatinine is also less than unity and increases with increasing intra-arterial doses. This indicates a saturable interaction at the luminal surface of the nephron. Saturation interaction at the luminal surface of the nephron. Saturation of postglomerular and luminal interactions can also be achieved by systemic preloading with unlabeled vitamin B12. After saturation the renal vein and urine recoveries for [3H]cyanocobalamin and creatinine become equal. However, significant differences can be observed between their renal vein mean transit times, depending on experimental conditions. During hydropenia [3H]cyanocobalamin behaves as a true extracellular marker and emerges in renal vein and urine outflows, superimposing on creatinine. During mannitol diuresis vitamin B12 still behaves as a glomerular marker, but its renal vein mean transit time is now significantly less than that of creatinine and its calculated postglomerular volume of distribution is reduced by approximately 15% of the available interstitial space.

Renal Elimination Kinetics and Plasma Half-Life of Oxalate in Man

The renal handling of oxalate was studied by the injection of 14C-oxalate together with inulin as a glomerular marker into the renal artery in 6 patients. From the recovered amounts of the injected substances in the urine, time-concentration curves were constructed. Oxalate was excreted into urine 2.31 +/- 0.05 (SE) fold when compared to inulin. The maximal concentration of oxalate occurred at the same time as inulin, and there was no urinary precession of oxalate in comparison to inulin. From this part of the study we conclude that oxalate in addition to its filtered amount can probably enter the early part of nephron. In a second type of study, plasma levels of oxalate and inulin were observed over a period of 180 min, following intravenous injections in 7 volunteers. The decline of oxalate plasma concentrations followed first-order kinetics. Calculation of the rate constants of elimination assuming the 'one compartment open' model resulted in an oxalate to inulin ratio of 1.21 +/- 0.05. The oxalate half-life of elimination was 92 +/- 8 min, whereas that of inulin amounted to 112 +/- 9 min. The higher value of the calculated volume of distribution of oxalate compared to that of inulin indicates that oxalate enters a larger space than the extracellular fluid volume. The urinary recovery of intravenously injected oxalate was 97.2 +/- 1.4%, indicating that oxalate is excreted exclusively by the kidney. The observed differences of oxalate excretion, obtained with these two methods, could be attributed to the higher amount of ionized oxalate in the disequilibrium technique (rapid injections), entering the urine in a higher rate. Such a mechanism could explain the hyperoxaluria in calcium oxalate stone-forming patients.

The Usefulness of125I-sodium lothalamate as a GFR-indicator in Single Intravenous Injection Tests

Clearance of sodium iothalamate was estimated from plasma elimination curves obtained from 90 patients having varying renal function, after a single intravenous injection of 125I-sodium iothalamate. The usefulness of sodium iothalamate as a GFR-indicator with this technique was tested by a strict statistical comparison with conventional inulin clearance as a reference. The regression line, covering the clearance range 2-163 ml min-1, Clinulin = 1.08.Clsodiumiothalamate-3.7, (n = 84, r = 0.85, SEE = 2.3 ml.min-1) was not significantly different from the identity line, which means (i) that extrarenal elimination could not be detected, and (ii) that I125-sodium iothalamate should be regarded as a useful glomerular marker for single intravenous injection studies. An open two-compartment model of mamillary type was found to give an adequate representation of the plasma disappearance curve. The results are not critically dependent on the choice of approximating function. The method by Sapirstein et al., the method by Nosslin and a power-law method were used for comparison and were found to give the same results. However, the present type of curve fitting analyses requires frequent blood sampling or external counting over a long period in order to give reliable estimates of GFR. This circumstance makes these methods less attractive for clinical use.

The early phase of experimental acute renal failure. II. tubular leakage and the reliability of glomerular markers.

Experiments were designed to determine whether leakage of substances across the tubular epithelium, which are impermeant in the normal kidney, falsifies the measurement of glomerular filtration rate in acute renal failure. Permeability to those substances most commonly used for filtration rate determination, polyfructosan, inulin and ferrocyanide, was estimated by measuring their recoveries following perfusion through various nephron segments in haeme pigment, ischaemic and nephrotoxic models of acute renal failure. Late proximal recovery of 14C ferrocyanide was only marginally decreased compared to controls, by a maximum of 6%. Distal recovery of polyfructosan, 14C and 3H inulin were depressed somewhat more, by a maximum of 11%. Urinary recovery of 14C inulin was reduced by only 15% in kidneys showing severely restricted renal function. It is concluded that tubular leakage is not a feature of significance in the early phase of moderate acute renal failure, that ferrocyanide and inulin are reliable markers for the determination of nephron filtration rate and water reabsorption, and that the reduction in whole kidney inulin or polyfructosan clearance reflects primarily a reduction in glomerular filtration rate.

The unreliability of mammalian glomerular markers in teleostean renal studies

1. The assumption that (3H) methoxy inulin, (14C) polyethylene glycol (PEG) and (125) iothalamate (glofil) are reliable volume and glomerular markers in teleosts was tested. 2. PEG occupied smaller volumes than inulin and glofil in sea-water-adapted Salmo gairdneri. Ureteral clearances of PEG were about 22% higher than those of inulin and glofil, and urine-to-plasma ratios were significantly greater for PEG than for the other two markers. 3. After introduction into the urinary bladder the three macro-molecules appeared in the plasma, PEG at the lowest rates. 4. These observations indicate that mammalian glomerular markers can penetrate the bladder and possibly the ureters and renal tubules. Therefore, their clearances may not give a true measure of glomerular filtration rates in teleosts.

The in vivo localization of high-affinity phlorizin receptors to the brush border surface of the proximal tubule in dog kidney

The interaction of [ 3H]phlorizin (spec. act. 5 Ci/mmole) with canine renal tubular surfaces has been investigated in vivo, using the multiple indicator dilution technique. 1. 1. Over short observation periods there is no observable interaction between tracer phlorizin and the antiluminal (peritubular) surface. Instead, phlorizin appears to have a limited volume of distribution relative to the extracellular reference (creatinine), from the postglomerular circulation. 2. 2. Phlorizin and creatinine are filtered to the same degree at the glomerulus however the urine recovery of [ 3H]phlorizin is 5–10% of the glomerular marker (plasma glucose concentration 60–124 mg/100 ml). 3. 3. The remaining 90–95% can be “washed off” and recovered in the urine within minutes after the systemic administration of a pulse of unlabelled phlorizin or glucose. Preloading of animals with phlorizin or glucose also increases the urine recovery of [ 3H]phlorizin relative to control conditions. In contrast the urine recovery of [ 3H]phlorizin is unaffected by phloretin infusion. 4. 4. It is concluded that only one set of high-affinity phlorizin receptors is present in dog kidney, and that these are located along the brush border of the proximal tubule, in close association with the glucose-transport mechanism.

Kinetics of ammonia production and excretion in the acidotic dog.

The Chinard technique of rapid injection into one renal artery of a glomerular marker (creatinine) and a compound whose utilization or excretion is under investigation has been employed in a study of the time courses of production and excretion of ammonia. Following the injection of N15H4 Cl or amide-N15-labeled glutamine, the label appeared in the urinary ammonia within a partially corrected time interval of 11 sec or less, suggesting that, in both instances, the labeled ammonia entered the urine as far along the nephron as the convoluted portion of distal tubules and cortical collecting ducts. Creatinine appeared in the urine after a delay of 60–100 sec. Following injections of amino-N15-labeled glutamine, appearance of label in urinary ammonia was delayed about 20 sec relative to that observed following injection of amide-N15-labeled glutamine. The time course of disappearance of label from the urine suggests that deamidation of glutamine is not rate-limiting for ammonia production and excretion, whereas deamination of glutamine may well be.