Urinary N-acetyl-beta-D-glucosaminidase Excretion Research Articles

The Role of Urinary N-acetyl-beta-glucosaminidase in Diagnosis of Kidney Diseases

N-acetyl-beta-D-glucosaminidase (NAG) is a lysosomal enzyme present in the proximal convoluted tubules of the kidneys that may be used as a marker of proximal tubular damage and nephrotoxicity. An abnormal urinary NAG excretion has been reported in different kinds of renal disorders such as acute kidney injury, urinary tract infection, vesicoureteral reflux; diabetes mellitus; nephrotic syndrome; glomerulonephritis; hypertension; perinatal asphyxia; heavy metals poisoning; drug nephrotoxicity, renal allograft rejection; and heart failure. This paper provides an overview of the diagnostic value of urinary NAG in the nephrourology field.Keywords: N-acetyl-beta-D-glucosaminidase; Acute Kidney Injury; Kidney Diseases; Pyelonephritis; Hypertension; Vesico-Ureteral Reflux.

Evaluation of urinary N-acetyl-beta-D-glucosaminidase as a marker of early renal damage in patients with type 2 diabetes mellitus

To evaluate the clinical usefulness of urinary N-acetyl-beta-D-glucosaminidase (NAG) excretion for the detection of early tubular damage in type 2 diabetes mellitus (T2DM). Thirty six patients with T2DM were divided into two groups based on urinary albumin to creatinine ratio (ACR): normoalbuminuria (ACR <30 mg/g; n=19) and microalbuminuria (ACR =30-300 mg/g; n=17). The following parameters were determined in both groups: urinary NAG and albumin, serum and urine creatinine, fasting plasma glucose and glycated hemoglobin (HbA1c). Urinary NAG levels [Units/g creatinine; median (range)] were significantly increased in microalbuminuria group [17.0 (5.9 - 23.3)] compared to normoalbuminuria group [4.4 (1.5 - 9.2)] (P<0.001). No differences between groups were observed in fasting glucose, HbA1c, serum creatinine levels and estimated glomerular filtration rates (eGFR). Urinary NAG positively correlated with ACR (r=0.628; p<0.0001), while no significant association was observed between NAG and glycemia, HbA1c, serum creatinine and eGFR. The increase of urinary NAG at the microalbuminuria stage of diabetic nephropathy (DN) suggests that tubular dysfunction is already present in this period. The significant positive association between urinary NAG excretion and ACR indicates the possible clinical application of urinary NAG as a complementary marker for early detection of DN in T2DM.

Association between Urinary N-Acetyl-Beta-D-Glucosaminidase and Microalbuminuria in Diabetic Black Africans

Diabetes mellitus is the commonest cause of ESRD worldwide and third most common cause in Nigeria. Recent reports from Nigeria indicate the prevalence of diabetic nephropathy as an aetiology of ESRD is increasing necessitating early diagnosis of diabetic nephropathy. We measured the urinary excretion of N-acetyl-beta-D-glucosaminidase (NAG), NAG/creatinine ratio, urinary protein-creatinine ratio and calculated eGFR in 30 recently diagnosed nonhypertensive diabetics and 67 controls. The age and sex distribution, systolic blood pressure, serum and urinary creatinine were similar for both groups. There was higher urinary excretion of NAG (304 versus 184 μmol/h/L, P < 0.001) and NAG/creatinine ratio (21.2 versus 15.7 μmol/h/L/mmolCr, P < 0.001) in the diabetics than controls. There was a strong correlation between NAG/creatinine ratio and albumin/creatinine ratio (r = 0.74, P < 0.001). A multivariate linear regression model showed a significant linear relationship between NAG/creatinine ratio and albumin/creatinine ratio after adjusting for the effect of blood pressure, age, sex, and serum creatinine. The strong association found between albumin/creatinine ratio and NAG/creatinine ratio perhaps indicates the need for further investigation of the clinical utility of NAG/creatinine ratio as a screening tool for early nephropathy in African diabetics.

Early Urinary Markers of Diabetic Kidney Disease: A Nested Case-Control Study From the Diabetes Control and Complications Trial (DCCT)

Urinary markers were tested as predictors of macroalbuminuria or microalbuminuria in patients with type 1 diabetes. Nested case-control of participants in the Diabetes Control and Complications Trial (DCCT). 87 cases of microalbuminuria were matched to 174 controls in a 1:2 ratio, while 4 cases were matched to 4 controls in a 1:1 ratio, resulting in 91 cases and 178 controls for microalbuminuria. 55 cases of macroalbuminuria were matched to 110 controls in a 1:2 ratio. Controls were free of micro-/macroalbuminuria when their matching case first developed micro-/macroalbuminuria. Urinary N-acetyl-beta-d-glucosaminidase (NAG), pentosidine, advanced glycation end product (AGE) fluorescence, and albumin excretion rate (AER). Incident microalbuminuria (2 consecutive annual AERs > 40 but < or = 300 mg/d) or macroalbuminuria (AER > 300 mg/d). Stored urine samples from DCCT entry and 1-9 years later when macro- or microalbuminuria occurred were measured for the lysosomal enzyme NAG and the AGE pentosidine and AGE fluorescence. AER and adjustor variables were obtained from the DCCT. Submicroalbuminuric AER levels at baseline independently predicted microalbuminuria (adjusted OR, 1.83; P < 0.001) and macroalbuminuria (adjusted OR, 1.82; P < 0.001). Baseline NAG excretion independently predicted macroalbuminuria (adjusted OR, 2.26; P < 0.001) and microalbuminuria (adjusted OR, 1.86; P < 0.001). Baseline pentosidine excretion predicted macroalbuminuria (adjusted OR, 6.89; P = 0.002). Baseline AGE fluorescence predicted microalbuminuria (adjusted OR, 1.68; P = 0.02). However, adjusted for NAG excretion, pentosidine excretion and AGE fluorescence lost the predictive association with macroalbuminuria and microalbuminuria, respectively. Use of angiotensin-converting enzyme inhibitors was not directly ascertained, although their use was proscribed during the DCCT. Early in type 1 diabetes, repeated measurements of AER and urinary NAG excretion may identify individuals susceptible to future diabetic nephropathy. Combining the 2 markers may yield a better predictive model than either one alone. Renal tubule stress may be more severe, reflecting abnormal renal tubule processing of AGE-modified proteins, in individuals susceptible to diabetic nephropathy.

Changes in the Urinary Excretion of .BETA.2-Microglobulin (.BETA.2MG) and N-acety-.BETA.-D-glucosaminidase (NAG) during Treatment for Lupus Nephritis

Tubulointerstitial involvement in the kidneys is frequently found but it is a less emphasized feature of lupus nephritis (LN). Recent studies have shown increases in the urinary excretion of beta2-microglobulin (beta 2MG) and N-acetyl-beta-D-glucosaminidase (NAG), which are considered to indicate the presence of tubulointerstitial damage, particularly in cases of LN. However, the changes in these urinary parameters during the clinical course of LN have not yet been fully clarified. In this report, we describe the changes in the urinary excretion of beta 2MG and NAG during immunosuppressive treatment combined with double filtration plasmapheresis in a case of LN.

Determination of urinary enzymes as a marker of early renal damage in diabetic patients

Diagnosis of diabetic nephropathy in the early stages is very important since there are no clinical signs or symptoms. Urinary N-acetyl-beta-D-glucosaminidase (NAG) excretion has been recommended as a tubular dysfunction marker that elevates before other markers, such as microalbuminuria and a decrease in creatinine clearance. In this study, we compared excretion of urinary enzymes with other markers that are used routinely in diabetic nephropathy assessment. Urinary NAG, lactate dehydrogenase (LDH), alkaline phosphatase (AP) activities, urea, creatinine, and albumin, with levels of serum glucose and creatinine and whole blood glycosylated hemoglobin (HbA1c) were measured in 32 diabetes mellitus patients and 25 healthy subjects (controls). Notably, urinary NAG, AP, LDH excretion, and microalbuminuria in the diabetic patients group were significantly increased compared to those in the control groups (P<0.001, P<0.05, P<0.01, and P<0.01, respectively). Meanwhile, our results showed that the urinary NAG excretion had the highest sensitivity and specificity (100% and 87.5%, respectively) compared to other markers. We showed that measuring urinary NAG excretion could be useful for the assessment of renal failure in diabetes mellitus patients and confirmed the use of NAG as a routine screening test.

Early markers of renal dysfunction in patients with sickle cell/β-thalassemia

Progressive renal failure is one of the main complications in HbS/beta-thalassemia (HbS/beta-thal). Early identification of patients at high risk of developing renal failure is of great importance as it may allow specific measures to delay the progression of renal damage and thus reduce the incidence of end-stage renal failure and mortality. Early predictors of renal impairment in HbS/beta-thal remain to explore. Within this context, we studied 87 compound HbS/beta-thal patients (36 males/51 females; median age 39 years) and 30 healthy controls. In addition to conventional renal biochemistries we measured serum cystatin-C (Cys-C), urine N-acetyl-beta-D-glucosaminidase (NAG) excretion and serum and urinary beta(2)-microglobulin (beta(2)-M). Cystatin-C, NAG and serum beta(2)-M levels were higher in patients than controls. The incidence of patients with high levels of Cys-C, NAG, and beta(2)-M was 32.1, 74.7, and 70.1% respectively, while only 6.8% of patients had increased serum creatinine levels. Cystatin-C and serum beta(2)-M showed a strong correlation with creatinine clearance and age, while NAG positively correlated with proteinuria. An inverse correlation was also shown between hemoglobin and beta(2)-M, NAG, and Cys-C levels. Seven patients with proteinuria received therapy with angiotensin-converting enzyme (ACE) inhibitors. Changes of poteinuria positively correlated with NAG levels. These results indicate that Cys-C is an accurate marker of renal dysfunction, and urinary NAG excretion can be considered as a reliable index of the tubular toxicity, and possible predictor of proteinuria and eventual renal impairment in HbS/beta-thal patients. Furthermore, NAG measurement may be used for monitoring ACE-inhibitors therapy in HbS/beta-thal patients with proteinuria.

MELATONIN REDUCES URINARY EXCRETION OF N‐ACETYL‐β‐d‐GLUCOSAMINIDASE, ALBUMIN AND RENAL OXIDATIVE MARKERS IN DIABETIC RATS

1. Increased oxidative stress has an important role in the pathogenesis of diabetic nephropathy. The aim of the present study was to evaluate diabetic nephropathy by determining markers of oxidative stress and the urinary excretion of N-acetyl-beta-D-glucosaminidase (NAG), albumin and to investigate the possible protective effects of in vivo melatonin on renal tubular oxidative damage in diabetic rats. 2. Twenty-six rats were randomly divided into three groups: (i) group I, control, non-diabetic rats (n = 9); (ii) group II, untreated diabetic rats (n = 8); and (iii) group III, melatonin-treated diabetic rats (n = 9). In groups II and III, diabetes developed 3 days after administration of a single dose of streptozotocin (35 mg/kg, i.p.). Thereafter, whereas the rats in group II received no treatment, rats in group III began to receive 10 mg/kg per day, i.p., melatonin for 8 weeks. Malondialdehyde (MDA), an index of lipid peroxidation, NAG and microalbumin in the urine, markers of renal tubular damage, were the parameters used for oxidative stress-induced renal injury. Superoxide dismutase (SOD), xanthine oxidase (XO) and glutathione peroxidase (GSH-Px) activities were determined to evaluate changes in the anti-oxidant status of kidney tissue. 3. In untreated diabetic rats, urinary NAG, albumin and renal MDA levels were markedly increased compared with control rats (P < 0.0001). However, these parameters were reduced in diabetic rats by melatonin treatment (P < 0.0001). Urinary excretion of NAG was positively correlated with the microalbuminuria and renal MDA levels (r = 0.8; P < 0.0001). The SOD and XO activities in the untreated diabetic group were found to be significantly higher than those of the control group (P < 0.0001). Superoxide dismutase and XO activities decreased in melatonin-treated rats compared with untreated diabetic rats (P < 0.002 and P < 0.023, respectively). However, the decrease did reach levels seen in control rats. There were no significant differences in GSH-Px activity between the three groups. 4. Therefore, on the basis of these data, we suggest that urinary NAG, albumin excretion, XO activity and MDA levels are more valuable parameters showing the degree of renal tubular injury than classical markers of oxidative stress, including SOD and GSH-Px, in diabetic rat kidneys. Melatonin has an ameliorating effect on oxidative stress-induced renal tubular damage via its anti-oxidant properties. Thus, it may be suggested that urinary NAG excretion and microalbuminuria may be important markers showing the degree of renal changes and the success of long-term treatment of renal impairment with melatonin.

Evaluation of Renal Functions in Asphyxiated Newborns

Renal injury due to perinatal asphyxia has not been systematically evaluated. The available studies have used variable definitions, incomplete investigations and none had a control group. The aim of this study was to evaluate systematically the renal functions in severely asphyxiated newborns and to find if abnormal renal function tests can predict adverse outcome (death or neurologic abnormality at discharge). In a prospective case-control design, 25 inborn babies>or=34 weeks gestation having asphyxia (5 min Apgar<or=6 or needing resuscitation>or=5 min) were enrolled as 'cases'. Simultaneously 25 gestation and weight matched babies with no asphyxia were enrolled as 'controls'. Renal function tests, calculated renal indices using timed urine collections and excretion of beta2-microglobulin and N-acetyl-beta-D-glucosaminidase (NAG) were monitored in both the groups for first 4 days of life. Fourteen (56 per cent) asphyxiated babies had acute renal failure (ARF) as compared to 1 (4 per cent) control (p=0.002). Blood urea and serum creatinine values were significantly higher in asphyxiated babies on day 4 but not on day 2. Renal failure index and FeNa were higher in asphyxiated babies on both day 2 and day 4, but creatinine clearance was not different. Urinary excretion of both beta2-microglobulin and NAG was higher in the asphyxiated babies on day 2 as well as day 4. Five minute Apgar<or=6 had the best sensitivity to predict renal failure. A combination of high serum creatinine and high blood urea had 100 per cent sensitivity and negative predictive value to predict adverse outcome while serum creatinine>1.5 mg/dl alone had the best specificity and positive predictive value. The renal parameters were however poorer predictors of adverse outcome in comparison to clinical markers like 5 min Apgar<or=3 and HIE stage II/III. Both glomerular and tubular involvement was seen commonly in babies with birth asphyxia. Clinical markers of asphyxia were better predictors of adverse outcome than renal function tests.

Time course study of oxidative and nitrosative stress and antioxidant enzymes in K2Cr2O7-induced nephrotoxicity

BackgroundPotassium dichromate (K2Cr2O7)-induced nephrotoxicity is associated with oxidative and nitrosative stress. In this study we investigated the relation between the time course of the oxidative and nitrosative stress with kidney damage and alterations in the following antioxidant enzymes: Cu, Zn superoxide dismutase (Cu, Zn-SOD), Mn-SOD, glutathione peroxidase (GPx), glutathione reductase (GR), and catalase (CAT).MethodsNephrotoxicity was induced in rats by a single injection of K2Cr2O7. Groups of animals were sacrificed on days 1,2,3,4,6,8,10, and 12. Nephrotoxicity was evaluated by histological studies and by measuring creatinine clearance, serum creatinine, blood urea nitrogen (BUN), and urinary excretion of N-acetyl-β-D-glucosaminidase (NAG) and total protein. Oxidative and nitrosative stress were measured by immunohistochemical localization of protein carbonyls and 3-nitrotyrosine, respectively. Cu, Zn-SOD, Mn-SOD, and CAT were studied by immunohistochemical localization. The activity of total SOD, CAT, GPx, and GR was also measured as well as serum and kidney content of chromium and urinary excretion of NO2 -/NO3-. Data were compared by two-way analysis of variance followed by a post hoc test.ResultsSerum and kidney chromium content increased reaching the highest value on day 1. Nephrotoxicity was made evident by the decrease in creatinine clearance (days 1–4) and by the increase in serum creatinine (days 1–4), BUN (days 1–6), urinary excretion of NAG (days 1–4), and total protein (day 1–6) and by the structural damage to the proximal tubules (days 1–6). Oxidative and nitrosative stress were clearly evident on days 1–8. Urinary excretion of NO2-/NO3- decreased on days 2–6. Mn-SOD and Cu, Zn-SOD, estimated by immunohistochemistry, and total SOD activity remained unchanged. Activity of GPx decreased on days 3–12 and those of GR and CAT on days 2–10. Similar findings were observed by immunohistochemistry of CAT.ConclusionThese data show the association between oxidative and nitrosative stress with functional and structural renal damage induced by K2Cr2O7. Renal antioxidant enzymes were regulated differentially and were not closely associated with oxidative or nitrosative stress or with kidney damage. In addition, the decrease in the urinary excretion of NO2-/NO3- was associated with the renal nitrosative stress suggesting that nitric oxide was derived to the formation of reactive nitrogen species involved in protein nitration.

Study of a rat model for calcium oxalate crystal formation without severe renal damage in selected conditions

Although nephrotoxic in high doses, ethylene glycol (EG) has been used with ammonium chloride (NH(4)Cl) or vitamin D(3) to study calcium oxalate stone formation in rat models. In the present study we used EG alone or with NH(4)Cl to study hyperoxaluria, crystaluria, and crystal attachment to renal epithelial cells in rats with minimal renal damage. Six-week-old male Sprague-Dawley (SD) rats were given food and special drinking water. In experiment 1 the drinking water contained 1.0% NH(4)Cl plus four different concentrations of EG (0.8%, 0.4%, 0.2%, 0.1%). In experiment 2 the drinking water contained EG alone (0.8%, 0.4%, 0.2%, 0.1%). Urine was collected for 24 h before the rats were sacrificed. In experiment 1 the rats were sacrificed 5-13 days after starting the special water. In experiment 2 the rats were sacrificed 7-21 days after starting the special water. Bladder urine was also obtained. Blood and urine were tested for calcium, phosphorus, and creatinine. In addition, urine was tested for pH, oxalate and N-acetyl-beta-D glucosaminidase (NAG). Kidney sections were stained with hematoxylin-eosin, von Kossa and Pizzolato stain. Crystal morphology was determined using polarizing microscopy, and composition was determined using high-resolution X-ray powder diffraction. Experiment 1: Aggravation of renal function, an increase in urinary oxalate and NAG excretion, and crystals observed in the kidneys all correlated with EG concentration and length of drinking time. In bladder urine, calcium oxalate monohydrate (COM) crystals exceeded calcium oxalate dihydrate (COD) crystals. Experiment 2: Renal function remained unchanged. Oxalate excretion increased and NAG increased slightly. Crystals occurred only in the papillary tip region. Crystals in bladder urine were mostly COD. In the current rat model, calcium oxalate crystaluria could be induced without severe renal damage in selected cases. Either and/or both COM and COD might form and interact with kidney epithelium. We propose different experimental conditions to study the various phases of calcium oxalate stone formation in young male SD rats.

A novel immunosuppressant FTY720 ameliorates proteinuria and alterations of intrarenal adrenomedullin in rats with autoimmune glomerulonephritis

FTY720 has been originally developed as a new immunosuppressive agent, which prolongs graft survival in organ transplantation. Adrenomedullin (AM) participates in the regulation of sodium homeostasis and has renoprotective effects. The possible involvement of renal AM in the pathophysiology of glomerulonephritis (GN) and the effect of FTY720 has been evaluated in rats. HgCl 2 (1 mg/kg body weight) was inoculated subcutaneously 3 times/week for a total of 2 weeks. FTY720 (3 or 10 mg/kg) was inoculated subcutaneously daily. The proteinuria, urinary N-acetyl-beta- d-glucosaminidase (NAG) excretion and serum total cholesterol levels were increased and serum albumin level was reduced in rats with HgCl 2-induced GN compared with controls. FTY720 reduced proteinuria (3 mg/kg: −25%; 10 mg/kg: −41%), urinary NAG excretion (−11%; −52%) and total cholesterol level (−21%; −55%) in a dose-dependent manner. Renal AM level and its mRNA expression were increased in rats with GN compared with controls (Peptide Cortex: +69%; Medulla: +82%; mRNA Cortex: +25%). Interestingly, FTY720 additionally increased these levels (Peptide Cortex: +38%; Medulla: +39%; mRNA Cortex: +20%). Renal AM levels correlated with urinary NAG excretion and creatinine clearance. These results suggest that FTY720 suppresses the renal damage in rats with GN and renal AM may participate in the pathophysiology of GN and the renoprotective effects of FTY720.

Relationship between Cisplatin or Nedaplatin-Induced Nephrotoxicity and Renal Accumulation

Nedaplatin is known to exhibit antitumor activity similar to that of cisplatin. However, concerning side effects, nedaplatin causes renal toxicity less frequently than cisplatin. In this study, we compared the incidence of renal toxicity between cisplatin and nedaplatin by investigating the difference in kidney tissue accumulation. Kidney tissue accumulation of cisplatin administered at 3.75 mg/kg was similar to that of nedaplatin administered at 24 mg/kg. At these doses, the plasma creatinine level and urinary excretion of glucose and N-acetyl-beta-D-glucosaminidase (NAG) similarly increased. There was a correlation between kidney accumulation of cisplatin and nedaplatin and the increases in plasma creatinine level and urinary excretion of NAG. Therefore, our results suggest that nedaplatin less frequently causes renal toxicity in comparison to cisplatin due to lower kidney accumulation.

Renal effects and erythrocyte oxidative stress in long-term low-level lead-exposed adolescent workers in auto repair workshops

Lead poisoning is an old but persistent public health problem in developing countries. The present study investigated blood lead levels and its effects on markers of renal function and parameters of erythrocyte oxidative stress in adolescent male auto repair workers in Turkey. Blood Pb level and the ALAD index (logarithm of activated delta-aminolaevulinic acid dehydratase/nonactivated delta-aminolaevulinic acid dehydratase) were measured as indicators of exposure to Pb. Markers of tubular damage urine N-acetyl-beta-D-glucosaminidase (NAG), beta2-microglobulin (beta-2 MG), creatinine (Cr), uric acid (UA), and calcium, markers of glomerular filtration blood urea nitrogen (BUN), serum Cr, UA, and parameters of oxidative damage in erythrocyte were studied in 79 Pb-exposed adolescent and 71 healthy control subjects. Blood lead levels and ALAD index were found significantly higher in the study group than that of normal control group. BUN, UA level, and glomerular filtration rates were detected in normal range in the lead-exposed group. Urinary NAG excretion and calciuria were higher in the study group than in controls. Urinary excretion of NAG was positively correlated with the blood lead levels (r=0.427). There was no relationship between blood lead levels and UA or beta-2 MG in urine. Malondialdehyde and glutathione peroxidase levels were significantly elevated in lead-exposed adolescents than controls, but changes in the catalase and superoxide dismutase activities in lead-exposed adolescents did not reach statistical significance. In conclusion, chronic low-dose lead exposure seems as a cause of subtle renal impacts in adolescent workers of auto repair workshops. Lead-induced oxidative stress in erythrocytes probably contributes to these subclinical renal effects.

Urinary PC-1 and N-acetyl-beta-D-glucosaminidase activity in patients with type 2 diabetes treated with metformin, gliclazide or glibenclamide.

Insulin resistance is a key feature of type 2 diabetes mellitus. Plasma cell differentiation antigen (PC-1) is an inhibitor of insulin receptor tyrosine kinase, and has been implicated in the pathogenesis of insulin resistance. Urinary excretion of PC-1 was determined in 45 newly detected, obese diabetic patients treated with metformin (16 patients), gliclazide (14 patients) or glibenclamide (15 patients). Urinary N-acetyl-beta-D-glucosaminidase (NAGA), a lysosomal enzyme, was determined as a marker of tubular damage in diabetes. Basal urinary PC-1 excretion in all three groups of diabetic patients was at the level of healthy controls. Treatment with oral hypoglycaemic drugs did not change significantly the group level or the number of patients in each group with increased PC-1 activity. Urinary excretion of NAGA in patients with type 2 diabetes was not statistically different from the control level. Metformin and gliclazide treatment did not change significantly the group levels of NAGA excretion. However, glibenclamide treatment produced an increased urinary NAGA excretion in the whole group, and in about twice as many patients as in the pre-treatment period.

Netilmicin Effect on Urinary Retinol Binding Protein (RBP) and N-Acetyl-Beta-D-Glucosaminidase (NAG) in Preterm Newborns with and without Anoxia

The study aim was to evaluate urinary excretion of Retinol Binding Protein (RBP), compared with urinary excretion of N-acetyl-β-D-glu-cosaminidase (NAG), in preterm infants with anoxia and netilmicin treatment. Urinary RBP and NAG were evaluated in 83 preterm newborns divided in 4 groups: 37 healthy preterm newborns (controls); 14 with neonatal anoxia; 16 treated with ampicillin + netilmicin; 16 with neonatal anoxia and treated with ampicillin + netilmicin. RBP was determined by an automated nephelometric technique and NAG by a colorimetric method on 5-h urine samples in the first week of life. Results showed that urinary excretion of RBP (average from first week values) was 1.06±0.67 g/mol creati-nine (mean ± SD) in controls, 1.99±1.41 in antibiotic-treated newborns, 3.99±4.57 in anoxic newborns and 3.75±3.48 in anoxic newborns under antibiotic treatment. When gestational age was not considered, a marked effect of anoxia (P<0.001) and a borderline effect of netilmicin (P<0.059) on RBP excretion were detected by ANOVA. However when gestational age was also considered by analysis of covariance, it appeared as the strongest predictor of RBP excretion (P<0.001), while the effect of netilmicin was no longer significant (P=0.181). The effect of anoxia persisted, although less remarkable (P=0.010). Conversely anoxia did not affect urinary NAG excretion, which was rather correlated with gestational age and netilmicin administration. The authors conclude that RBP and NAG urinary excretion may be used to discriminate between neonatal anoxia and netilmicin treatment, respectively as etiologic factors of renal tubular damage in the newborn.

Occupational exposure to airborne mercury during gold mining operations near El Callao, Venezuela.

The National Institute for Occupational Safety and Health (NIOSH) recently conducted a cross-sectional study during gold mining operations near El Callao, Venezuela. The purpose of the study was to assess mercury exposures and mercury-related microdamage to the kidneys. The study consisted of concurrent occupational hygiene and biological monitoring, and an examination of the processing techniques employed at the different mining facilities. Mercury was used in these facilities to remove gold by forming a mercury-gold amalgam. The gold was purified either by heating the amalgam in the open with a propane torch or by using a small retort. Thirty-eight workers participated in this study. Some participants were employed by a large mining company, while others were considered "informal miners" (self-employed). Mercury exposure was monitored by sampling air from the workers' breathing zones. These full-shift air samples were used to calculate time-weighted average (TWA) mercury exposure concentrations. A questionnaire was administered and a spot urine sample was collected. Each urine sample was analyzed for mercury, creatinine, and N-acetyl-beta-D-glucosaminidase (NAG). The range for the 8-h TWA airborne mercury exposure concentrations was 0.1 to 6,315 micrograms/m3, with a mean of 183 micrograms/m3. Twenty percent of the TWA airborne mercury exposure measurements were above the NIOSH recommended exposure limit (REL) of 50 micrograms/m3, and 26% exceeded the American Conference of Governmental Industrial Hygienists (ACGIH) threshold limit value (TLV) of 25 micrograms/m3. The mean urine mercury concentration was 101 micrograms/g creatinine (microgram/g-Cr), and the data ranged from 2.5 to 912 micrograms/g-Cr. Forty-two percent of the study participants had urine mercury concentrations that exceeded the ACGIH biological exposure index (BEI) of 35 micrograms/g-Cr. Urinary NAG excretion is considered a biological marker of preclinical, nonspecific microdamage to the kidney's proximal tubule cells. The mean urine NAG concentration was 3.6 International Units/g-Cr (IU/g-Cr) with a range of 0.5 to 11.5 IU/g-Cr. Three workers had urine NAG levels in excess of the reference values. Correlation analyses found statistically significant correlations between airborne mercury exposure and urine mercury level (P = 0.01), and between urine mercury level and urine NAG excretion (P = 0.01). In addition, the airborne mercury exposure data and urine mercury data were segregated by job tasks. A Wilcoxon rank sum test revealed significant correlations between tasks and mercury exposure (P = 0.03), and between tasks and urine mercury level (P = 0.02). The tasks with the highest mean airborne mercury exposures were "burning the mercury-gold amalgam" and "gold refining/smelting". Recommendations were provided for improving the retort design to better contain mercury, for ventilation in the gold shops, and for medical surveillance and educational programs.

Dietary potassium and magnesium supplementation in cyclosporine-induced hypertension and nephrotoxicity

Cyclosporine A (CsA)-induced hypertension and nephrotoxicity are aggravated by high sodium intake. Accumulating evidence suggests that potassium and magnesium supplementation could protect against the detrimental effects of dietary salt. In the present study, we tested the hypothesis of whether concurrent supplementation with potassium and magnesium could protect against the development of CsA-induced hypertension and nephrotoxicity more effectively than supplementation with one mineral alone. Eight-week-old spontaneously hypertensive rats (SHRs) were divided into four groups (N = 10 in each group): (1) CsA group (5 mg/kg subcutaneously) receiving high-sodium diet (Na 2.6%, K 0.8%, Mg 0.2% wt/wt); (2) CsA group receiving a high-sodium, high-potassium diet (Na 2.6%, K 2.4%, Mg 0.2%); (3) CsA group receiving high-sodium, high-magnesium diet (Na 2.6%, K 0.8%, Mg 0.6%); and (4) CsA group receiving high-sodium, high-potassium, high-magnesium diet (Na 2.6%, K 2.4%, Mg 0.6%). CsA induced severe hypertension and deteriorated renal functions in SHRs on high-sodium diet. Histologically, the kidneys showed severe thickening of the media of the afferent artery with fibrinoid necrosis. Potassium supplementation lowered blood pressure (198 +/- 5 vs. 212 +/- 2 mm Hg, P < 0.05) and partially prevented the development of proteinuria (-25%, P < 0.05). Magnesium supplementation decreased blood pressure to the same extent but improved renal functions more effectively than potassium. The greatest protection against CsA toxicity was achieved when dietary potassium and magnesium supplementations were combined. Urinary N-acetyl-beta-D-glucosaminidase (NAG) excretion, a marker for renal proximal tubular damage, increased progressively in CsA-treated SHRs on the high-sodium diet. Neither potassium nor magnesium influenced urinary NAG excretion. We also estimated the activity of the renal dopaminergic system by measuring 24-hour urinary dopamine excretion rates. CsA suppressed the renal dopaminergic system during high-sodium diet. Magnesium supplementation, alone and in combination with potassium, protected against the development of renal dopaminergic deficiency in CsA-treated SHRs on high-sodium diet. Magnesium supplementation increased plasma-free ionized magnesium (iMg) and bone magnesium by 50 and 16%, respectively. Our findings indicate that both potassium and magnesium supplementations showed beneficial effects against CsA-induced hypertension and nephrotoxicity. The protective effect of magnesium clearly exceeded that of potassium. The greatest protection against CsA toxicity was achieved when potassium and magnesium were combined. We also provide evidence that the development of CsA-induced glomerular, tubular, and vascular lesions are associated with renal dopaminergic deficiency.

Influence of retrieval conditions on renal medulla injury: evaluation by proton NMR spectroscopy in an isolated perfused pig kidney model.

Delayed graft function (DGF) has remained an important complication after renal transplantation. The exact causes of DGF remain to be clarified, particularly the impact of retrieval conditions and preservation factors. In the present investigation, (1)HNMR spectroscopy of urine was assessed in order to detect the influence of retrieval condition on renal medulla damage. The isolated perfused pig kidney (IPK) was used to assess initial renal function from multiorgan donors (MOD) or single organ donors (SOD) after in situ cold flush and 24-h cold storage (CS) preservation with two standard preservation solutions: Euro-Collins (EC) and University of Wisconsin (UW) solutions. Kidneys flushed with cold heparinized saline and immediately perfused were used as the control group. Kidneys were perfused for 90 min at 37.5 degrees C for functional evaluation. During reperfusion, renal perfusion flow rate (PF) was measured. Glomerular filtration rate (GFR), tubular reabsorption of Na(+), and lactate dehydrogenase (LDH) and N-acetyl-beta-d-glucosaminidase (NAG) excretions were determined. Ischemia-reperfusion impairment was also determined by histological techniques and (1)HNMR spectroscopy. PF, GFR, and tubular reabsorption of Na(+) were significantly decreased in experimental groups when compared to the control group but there was no significant difference between experimental SOD groups. GFR was significantly greater in UW-MOD than in EC-MOD and tubular reabsorption of Na(+) was significantly greater in UW-MOD than in EC-MOD after 45 min of reperfusion. The release of LDH in the effluent and the urinary excretion of NAG were not significantly different after 24-h CS in the various experimental groups. The most relevant resonances determined by (1)HNMR spectroscopy were citrate, trimethylamine-N-oxide, lactate, acetate, and amino acids. Excretion of these markers was significantly different when compared to biochemical markers. A resonance (P) detected particularly in EC-MOD after 24-h CS was identified and well correlated to renal dysfunction. Histological study showed that ultrastructural damage and mitochondrial injury were more pronounced in the EC-MOD group. These results show that retrieval condition influences renal medullary damage. NMR spectroscopy, which is a noninvasive and nondestructive technique, is more efficient in assessing renal damage than conventional histology and biochemical analysis.

Human parathyroid hormone (1-34) transiently increases the excretion of lysosomal enzymes into urine and the size of renal lysosomes.

It has been reported that the urinary excretion of N-acetyl-beta-D-glucosaminidase (NAG), a lysosomal enzyme, transiently increases in human after treatment with human parathyroid hormone (hPTH)(1-34). We report here that hPTH(1-34) caused transient changes in the size and density of rat renal lysosomes following urinary excretion of NAG and other lysosomal enzymes tested. Percoll density gradient centrifugation revealed that hPTH(1-34) slightly but significantly increased the fraction of high density lysosomes (around 1.12 g/ml) 5-10 min after the treatment with hPTH(1-34), with a concomitant decrease in the fraction of intermediate density lysosomes (1.07-1.08 g/ml). On electron micrographs, some lysosomes in proximal tubules but not in distal tubules showed a change in morphology from circular to oval, and became enlarged and electron-dense 5-10 min after the treatment with hPTH(1-34). These responses to hPTH(1-34) were also reversible and transient. NAG excreted in urine after treatment with hPTH(1-34) had the molecular mass of a mature form in lysosomes and/or endosomes and was not a prepro-and/or pro-form of the enzyme. Thus, the changes in the density and size of renal lysosomes appear to be associated with the exocytosis of lysosomal enzymes by hPTH(1-34).