Novel oligo(ethylene glycol)-based molecularly imprinted magnetic nanoparticles for thermally modulated capture and release of lysozyme

In this study, oligo(ethylene glycol) (OEG)-based thermoresponsive molecularly imprinted polymers (MIPs) for lysozyme on the surface of magnetic nanoparticles were synthesized. Thermoresponsive monomer 2-(2-methoxyethoxy)ethyl methacrylate, chelate monomer N-(4-vinyl)-benzyl iminodiacetic acid, and acidic monomer methacrylic acid were selected as the ingredients for preparing the MIP layer. The thermoresponsive behavior of the novel imprinted magnetic nanoparticles was evaluated by dynamic light scattering and swelling ratios measurements. Interestingly, in analysis of lysozyme, the capture/release process could be modulated by changing the temperature, avoiding tedious washing steps. Meanwhile, high adsorption capacity (204.1 mg/g) and good selectivity for capturing lysozyme were achieved. Additionally, surface imprinting with magnetic nanoparticles as substrate allowed for short adsorption time (2 h) and rapid magnetic separation. Furthermore, the proposed imprinted magnetic nanoparticles were used to selectively extract lysozyme in human urine with recoveries ranging from 89.2% to 97.3%. The results indicated that the OEG-based monomers are promising for responsive MIP preparation, and the proposed imprinted material is efficient for thermally modulated capture and release of target protein.

Synthesis of magnetic molecularly imprinted poly(ethylene-co-vinyl alcohol) nanoparticles and their uses in the extraction and sensing of target molecules in urine

Superparamagnetic nanoparticles are of great current interest for biomedical applications in both diagnostics and treatment. Magnetic nanoparticles (MNP) can be manipulated by magnetic fields, so that when functionalized, they can be used for the purification and separation of biomolecules and even whole cells. Here we report combining the separation capabilities of MNPs with the functional (binding) capability of molecularly imprinted polymers. Albumin- creatinine-, lysozyme-, and urea-imprinted polymer nanoparticles were synthesized from poly(ethylene-co-ethylene alcohol) via phase inversion, with both target molecules and hydrophobic magnetic nanoparticles mixed within the polymer solution. Several ethylene:ethylene alcohol mole ratios were studied. The rebinding capacities for those three target molecules varied from 0.76 +/- 0.02 to 5.97 +/- 0.04 mg/g of molecularly imprinted magnetic nanoparticles. Lastly, the composite nanoparticles were used for separation and sensing of template molecules (e.g., human serum albumin) in real samples (urine) and results were compared with a commercial ARCHITECT ci 8200 system.

Hyperreninemia, lysozymuria, and erythrocytosis in Fanconi syndrome with medullary cystic kidney

Adult onset Fanconi syndrome with medullary cystic kidney was diagnosed in a 30-year-old male with muscular weakness, hypokalemia, normal BP, hyperreninemia, and secondary aldosteronism. He also had non-specific aminoaciduria, lysozymuria, and beta 2-microglobulinuria. Urinary concentrating and acidifying capacity was impaired, and both sodium and potassium were lost into the urine. I.v. pyelography revealed medullary cystic kidney. Renal biopsy showed juxtaglomerular hyperplasia, heavy subintimal deposits and C3 and IgG in preglomerular arteriolar walls, and degenerative changes in the tubules, including loss of brush border and "macula densa-like" lesions. Polycythemia with elevated serum erythropoietin levels, and raised blood ACTH values with features of cortisolism were also present. Indomethacin therapy decreased plasma renin activity (PRA), plasma aldosterone, and urinary loss of potassium and sodium, while serum potassium approached normal levels. Metoprolol, a beta-adrenergic blocking agent, caused similar effects. Insensitivity to the pressor effect of angiotensin II was reversed by indomethacin treatment. Somatostatin infusion lowered PRA and aldosterone without affecting BP. Several biochemical aberrations of this patient resemble Bartter's syndrome, including the effect of indomethacin.

The urinary excretion of ten plasma proteins in long-term renal transplant patients

Using an automated immunoprecipitin reaction, the urinary excretion of albumin, transferrin, haptoglobin, IgM, IgG, IgA, free lambda and kappa light chains from immunoglobulin, lysozyme and beta2-microglobulin has been investigated in 40 long-term bilaterally nephrectomized renal transplant patients. The excretion of the proteins, except lysozyme, was significantly increased in 21 of the paitents with Albustix-negative urine. In patients with glomerulonephritis prior to the transplantation, the excretion of albumin, transferrin, and IgG was significantly increased compared with the other patients. The IgM excretion was significantly increased in patients who had received C and D matches compared with those with A and B matches. Patients with severe surgical complications in the postoperative period had a tubular proteinuria, and in patients surviving more than 60 months after transplantation the excretion of several proteins was significantly increased compared with patients surviving less than 60 months.

Urinary excretion of ten plasma proteins in patients with febrile diseases

The 24-hour urinary excretion of albumin, transferrin, haptoglobin, IgG, IgA, IgM, free lambda and kappa light chains from immunoglobulin, lysozyme, and beta2-microglobulin has been investigated in 22 patients with febrile diseases, using an automated immunoprecipitin reaction. The average excretion of the 10 proteins was significantly increased in the patients compared with a control group. In patients with body temperature is greater than or equal to 38.5 degrees C the tubular type of proteinuria was significantly increased compared with those with body temperature is less than 38.5 degrees C. Sequential studies in 10 patients showed that the tubular type of proteinuria occurred in all, whereas the glomerular type was demonstrated in 8. when the fever had subsided, the tubular proteinuria disappeared rapidly i in all patients, while the glomerular proteinuria disappeared in only 4 out of 8. It was shown that tubular proteinuria was caused by fever per se, and it is suggested that glomerular prteinuria might be due to an immue response to antigens, derived from the infectious agents, producing a transient or permanent glomerular injury.

Modulation of the transforming growth factor beta1 by vitamin E in early nephropathy

OBJECTIVE

The aim of this study was to investigate the pharmacological activity of an antioxidant, alpha-tocopherol (vitamin E, VE) in streptozotocin-induced diabetic rats and study its role in modulating the transforming growth factor beta1 (TGF-beta1).

METHODS

Male Sprague-Dawley rats were treated with streptozotocin to induce diabetes. VE and/or insulin (INS) were administered daily during treatment periods of 3, 5, 7 and 10 days. Plasma glucose and fructosamine were measured in diabetic rats at the end of each treatment period. Samples of plasma, urine and renal cortex were analyzed for changes in protein and lysozyme excretion, reduced glutathione and malondialdehyde formation. TGF-beta1 was determined by ELISA and expression of TGF-beta1 mRNA was investigated by RT-PCR and Northern blot analysis.

RESULTS

Diabetes-induced glycemic stress was suppressed by INS, VE or a combination of INS and VE. Diabetes-induced increases of glucose, protein and lysozyme excretion were markedly depressed after 10-day treatment with INS, VE and the combination of INS and VE. Decreased glutathione content in the renal cortex of diabetic rats recovered towards control values, especially after 10-day treatment. Malondialdehyde content increased in diabetic rats and was reduced towards control value following 7- and 10-day treatments. Treatment of diabetic rats with INS, VE or the combination of INS and VE decreased elevated TGF-beta1 in plasma, decreased excretion of TGF-beta1 in urine, and decreased renal cortex TGF-beta1 mRNA levels.

CONCLUSIONS

Diabetes-induced overexpression of TGF-beta1 mRNA was suppressed by VE and INS after 5-, 7- and 10-day treatments. The results obtained with the antioxidant VE suggest that oxidative stress is involved in the development of diabetic nephropathy. Therefore, VE treatment may be effective in early stages of diabetic nephropathy to decrease or prevent pathological complications.

Lysosomal enzymes in preeclamptic women in northern Nigeria

BACKGROUND

The incidence of preeclampsia is high in northern Nigeria, as it is in many other developing countries, and preeclampsia is associated with significant maternal and fetal morbidity and mortality. We inquired if proteinuria or hypertension alone could account for the altered concentrations of urinary lysosomal hydrolases that have been reported in preeclamptic women and pregnant women without preeclampsia.

METHODS

The activities of urinary beta-hexosaminidase and beta-galactosidase were determined fluorometrically in pregnant women assigned to one of four groups: Group I: 41 preeclamptic women; Group II: 31 hypertensive aproteinuric women; Group III: 44 normotensive proteinuric women; and Group IV: 52 healthy pregnant women (controls).

RESULTS

The urinary beta-hexosaminidase concentrations were decreased in the preeclamptic women (P<0.005) and proteinuric women (P<0.001) when compared to the healthy pregnant controls. There was no significant difference in beta-hexosaminidase concentrations between the hypertensive women and the healthy pregnant controls. The urinary beta-galactosidase concentrations for preeclamptic, hypertensive, and proteinuric women did not differ significantly versus healthy pregnant controls.

CONCLUSIONS

The reduced urinary excretion of beta-hexosaminidase in preeclamptic women is associated with proteinuria, but not hypertension. Measuring urinary concentrations of lysosomal hydrolases alone or in conjunction with urinary protein concentrations is not likely to be useful in predicting or monitoring the clinical course of preeclampsia; however, it might prove important in gaining a more complete understanding of the pathogenesis of renal tubular epithelial cell injury and proteinuria that occurs in preeclampsia.

Laparoscopic right nephrectomy for live kidney donation: functional results

Laparoscopic live-donor nephrectomy has gained wide acceptance. However, the vast majority of surgeons perform left nephrectomies only, which may not always be in the best interest of the donor. Of 17 consecutive laparoscopic donor nephrectomies, 13 were done on the right side. The function of these grafts was compared with that of 17 kidneys previously procured by an open technique and with that of the four left laparoscopic grafts. Ischaemic damage was evaluated by post-operative nuclear scanning and urinary lysozyme, and graft function by creatinine and creatinine clearance. Results show that operating time was longer in the laparoscopic donors, but identical in right and left laparoscopic procurements. Ischaemic damage and function were similar, regardless of the side or the surgical technique. We can conclude that right laparoscopic donor nephrectomy is feasible and results in good graft function. Systematic harvesting from the left side may, therefore, not be justified.

Hereditary renal amyloidosis caused by a new variant lysozyme W64R in a French family

BACKGROUND

The number of proteins with mutations resulting in amyloidosis has continued to increase. Five proteins--transthyretin, fibrinogen alpha-A chain, apolipoprotein AI, lysozyme, apolipoprotein AII, cystatin C and gelsolin--can be associated with hereditary amyloidosis involving the kidney.

METHODS

A French family with a history of autosomal dominant hereditary amyloidosis with early sicca syndrome and nephropathy leading to renal failure after the fifth to the seventh decade was studied. Several tissue specimens obtained from the proband and his relatives were examined. Immunohistochemistry was performed on paraffin embedded sections using the indirect immunoperoxidase technique. We searched for mutations in the five exons and flanking introns of the lysozyme gene.

RESULTS

Amyloid deposits from the bowel, labial salivary gland and kidney were intensively stained by anti-lysozyme antibody. Sequence analysis of lysozyme exon 2 from the affected individuals revealed a nucleotide substitution predicting a substitution of the amino acid at position 64 in the mature protein from tryptophane, an aromatic residue to the cationic residue arginine (W64R).

CONCLUSION

We report a novel mutation (W64R) of the lysozyme that is associated with hereditary amyloidosis and prominent nephropathy. Since the treatment of hereditary amyloidosis greatly varies with the nature of the amyloid protein, thorough characterization of the latter is crucial for the management of the disease.

Potentials and limitations of the low-molecular-weight protein lysozyme as a carrier for renal drug targeting

Selective targeting of drugs to the kidney may enable an increased renal effectiveness combined with a reduction of extrarenal toxicity. Intrarenal delivery to the proximal tubular cell can be achieved using low-molecular-weight proteins, such as lysozyme. Administration of high dosages of lysozyme, required to study the effects of such conjugates in vivo, however, is restricted since a partial escape of the renal reabsorption and the occurrence of unwanted effects on systemic blood pressure and renal function may occur. The purpose of this study was to investigate the optimal parenteral administration schedule and the maximum dose of lysozyme, providing the most optimal tubular reabsorption and at the same time a minimal effect on blood pressure and renal hemodynamics, comparing continuous infusion of lysozyme with single dose injections. Urinary lysozyme excretion increased dose-dependently, both during continuous infusion and intravenous bolus injections. However, this loss of intact lysozyme into the urine was much higher after 3 injections of in total 250 mg x kg(-1) x 6 h(-1) (51.8+/-3.7% of the dose) compared to the same dose administered by continuous infusion (11.7+/-2.4%, P < 0.001). Continuous infusion of lysozyme up to 1000 mg x kg(-1) in 6 hours had no effect on systemic blood pressure, whereas a bolus injection of lysozyme (167 mg x kg(-1)) resulted in reversible blood pressure lowering of 52.2+/-2.2% (P<0.001). A dose-dependent decline of the glomerular filtration rate was observed at dosages of lysozyme higher than 100 mg x kg(-1) x 6 h(-1), with a maximal reduction of 53.0+/-3.7% after infusion of 1000 mg x kg(-1) x 6 h(-1). Effective renal plasma flow was less affected and only lowered statistically significant at dosages of 500 (-12.6+/-3.3%, P<0.05) to 1000 mg x kg(-1) x 6 h(-1) (-17.2+/-3.9%, P<0.01). We conclude that bolus injections of lysozyme should not be used for renal targeting purposes since it results in considerable tubular loss of lysozyme in the urine as well as cardiovascular side effects. In contrast, continuous infusion of lysozyme using dosages sufficient for renal drug targeting (maximally 15 mg x kg(-1) x h(-1)) only has minimal effects on blood pressure and renal hemodynamics, with a minimal urinary lysozyme loss as well.

[The method for detection of urinary lysozyme]

A method for lysozyme measurement in the urine is developed, based on adsorption of lysozyme molecules on the surface of chitin. The urine of healthy children, men, and women contains 1.76, 1.51, and 1.69 mg/liter lysozyme, respectively. Urinary lysozyme values in some diseases are presented.

Possible correlation between urinary muramidase (E.C.3.2.1.27) and oesophageal cancer

The diagnostic value of determination of low-mass enzymes in urine is very important, especially for early detection of some diseases. There are several investigations about lysozyme (muramidase, E.C.3.2. 1.27) and its correlation with some malignancies, but until now nothing has been reported about the lysozyme, and oesophageal cancer. This study was undertaken for determination of lysozyme concentration in urine of 32 oesophageal cancer patients to evaluate if this enzyme activity changes in oesophageal cancer used for detection of this cancer especially in its early stage. We used high performance liquid chromatography (HPLC) for determination of urinary muramidase after Sep-pac pre-purification of the samples. The mean results of lysozymuria in patients in comparison with the mean of enzyme activity in normal controls were statistically high (12.14+/-0.403 vs. 2.04+/-0.134, P</=0.001) Our finding also indicated that the severity of lysozymuria in these patients is stage dependent.

Microparticle-enhanced nephelometric immunoassay of lysozyme in milk and other human body fluids

Quantitation of lysozyme in human milk was performed by a microparticle-enhanced nephelometric immunoassay based on the measurement of the light scattered during the competitive immunoagglutination of a microparticle-lysozyme conjugate with an anti-lysozyme antiserum. This immunoassay has a detection limit of 8 microg/L of reaction mixture and can be performed using diluted milk (1:6000, in reaction mixture), excluding sample pretreatment. Human milk lysozyme can be quantified over the concentration range 0.09-1.50 g/L, with within- and between-run coefficients of variation <5%. Changes in the lysozyme concentration of human milk during lactation were determined in 636 samples. Lysozyme concentrations (mean +/- SE) decreased from colostrum (0.36 +/- 0.02 g/L) to transitional milk (0.30 +/- 0.01 g/L) and mature milk during days 15-42 (0.30 +/- 0.01 g/L), then increased in the mature milk during days 43-56 (0.35 +/- 0.01 g/L) and especially during days 57-84 (0.83 +/- 0.05 g/L). The proportion of lysozyme contributing to total protein was found to rise during lactation and was as follows: colostrum (1.7%), transitional milk (2.3%), and mature milk from days 15-28 (2.7%), days 29-42 (3.1%), days 43-56 (3.8%), and days 57-84 (7.3%). The assay developed for milk was also suitable for the determination of lysozyme in other human body fluids.

Drug delivery to the kidneys and the bladder with the low molecular weight protein lysozyme

The low molecular weight protein (LMWP) lysozyme is a suitable drug carrier for renal drug targeting. When the tubular reabsorption of a LMWP can be prevented, the protein will be excreted in the urine. In this way, lysozyme (LZM) conjugates might also be used as carriers for targeting to the urinary tract. Since positive domains on the protein surface are important for the interaction with the tubular uptake-receptor, we studied the urinary excretion of a drug-LZM conjugate with and without positive charge on the LMWP. We synthesized two conjugates with the fluorescent compound fluorescein. A positively charged conjugate was obtained by reacting fluorescein isothiocyanate (FITC) with LZM at a 1:1 molar to molar ratio; this conjugate contained six free primary aminogroups. The conjugate without positively charged groups was obtained by reacting the remaining free primary aminogroups of the FITC-LZM with succinic anhydride (Suc). The Suc-FITC-LZM contained only 0.2 free primary aminogroups per molecule. We studied the pharmacokinetics of the conjugates in freely moving Wistar rats. The FITC-LZM conjugate was excreted intactly into the urine for 29 +/- 4% of the injected dose. The Suc-FITC-LZM was excreted into the urine intactly for 45 +/- 4%. These data indicate that the excretion of a drug-LMWP conjugate into the urine can be increased by decreasing the positive charge on the carrier surface. Such a carrier may be an attractive candidate for drug targeting to the bladder.

Renal function in full-term neonates with hyperbilirubinemia

The purpose of this study was to investigate the effect of unconjugated hyperbilirubinemia on endogenous creatinine clearance and urinary excretion of sodium, phosphorus, lysozyme, and amino acids in full-term infants. Thirty-seven healthy, breast-fed newborns who were not exposed to phototherapy were studied on their third to fifth day of life. Twenty had neonatal hyperbilirubinemia with a mean indirect bilirubin value of 16.4 mg/dl, whereas 17 who were used as controls had a mean indirect bilirubin value of 7.8 mg/dl. Urine was collected, and samples were taken for examination of creatinine, lysozyme, sodium, and phosphorus concentration. Urinary sediment, glucose, and amino acid levels were also measured. Serum total and direct bilirubin, creatinine, sodium, and phosphorus measurements were taken at the beginning of urine collection. Calculations were made for creatinine clearance, fractional excretion of sodium (FENa), and tubular reabsorption of renal phosphate per deciliter glomerular filtrate (TP/GFR). The means (+/-1 SD) of creatinine clearance, FENa, and TP/GFR were 27.0 +/- 14.2 ml/min/1.73 m2, 0.53% +/- 0.49%, and 5.72 +/- 1.16 mg/dl GF, respectively, in the hyperbilirubinemic group compared with 21.1 +/- 9.4 ml/min/1.73 m2, 0.4% +/- 0.47%, and 6.01 +/- 0.51 mg/dl GF, respectively, in the controls. No statistically significant differences were found between the groups for any of the examined parameters of either glomerular or tubular function. Neonatal hyperbilirubinemia < 20.8 mg/dl has no detrimental effect on renal function of healthy, breast-fed, full-term newborns, and no modification in the approach regarding renal function is necessary in these babies.

Effective method for purification of lysozyme from human urine

Lysozyme in the urine of a hemodialysis patient was purified in two steps: DEAE Sephadex chromatography followed by Sephacryl chromatography. The Sephacryl S-100 column chromatographed fraction showing lytic activity was proven to give one band on SDS-PAGE and to have a molecular mass of 14500, in agreement with that of lysozyme. The N-terminal amino acid sequence of this purified protein was identical to that of lysozyme. These results indicate that the protein purified was indeed lysozyme. The specific affinity of lysozyme for Sephacryl S-100 may explain the greater purity of the same protein isolated by this method.

[Clinical significance of changes of urinary enzymes in pregnancy induced hypertension]

OBJECTIVE

To study the clinical significance of changes of N-acetyl-beta-D-glucosaminidase (NAG) and lysozyme in random urine sample in pregnancy induced hypertension (PIH).

METHODS

The concentration of NAG was measured by oronitrophenol spectrophotometric methods, and the concentration of lysozyme by agar plate diffusion method. Random urine samples from 266 pregnant women were examined, 110 cases were normal pregnant women, 156 cases were PIH patients.

RESULTS

(1) The level of NAG and lysozyme in moderate and severe PIH patients were significantly higher than that in mild PIH patients and normal pregnant women (P < 0.01) and it increased with the severity of disease. (2) There was a positive correlation between NAG and protein/creatinine (Pr/Cr) ratio in random urine. (3) There was a positive correlation between urinary lysozyme and serum beta 2-microglobulin (r = 0.874, P < 0.05).

CONCLUSION

Determination of urinary NAG and lysozyme levels will differentiate various states of PIH.

Tubular toxicity is the main renal effect of contrast media

The aim of this study is to evaluate the effects of contrast media on both tubular and glomerular function. Different parameters of tubular and glomerular function were determined before and at 1, 3, and 5 days after the intravascular administration of contrast media in 100 adult renal patients (plasma creatinine 0.6-10.8 mg/dL, mean: 1.3). Urinary activities of five tubular enzymes (alanine aminopeptidase, gamma-glutamyltransferase, alkaline phosphatase, lactate dehydrogenase, N-acetyl-beta-D-glucosaminidase) increased significantly on the first day after the administration of contrast media, indicating a tubular damage. Glomerular filtration rate and the conventional tests of glomerular function (plasma creatinine, creatinine clearance, and urinary proteins) presented only slight variations after the administration of contrast media. In conclusion, contrast media principally affected the renal tubule (as demonstrated by enzymuria), while their effects on glomerular function were very mild.

Usefulness and limitations of serum and urine lysozyme levels in the classification of acute myeloid leukemia: an analysis of 208 cases

The revised French-American-British (FAB) classification system for acute myeloid leukemia (AML) recommends the determination of serum lysozyme (SL) or urine lysozyme (UL) levels as an aid in distinguishing acute myeloblastic leukemia with maturation (FAB M2) from acute myelomonocytic leukemia (M4). We reviewed retrospectively 208 cases of adult leukemia in which SL and/or UL were obtained. Elevated lysozyme levels were not found in any of the M0, M3, or M7 cases, but were increased (false positive) in three (14%) M1 cases, 18 (19%) M2 cases and one (20%) M6 case. Although a UL value in excess of 3x normal was found in most cases of AML M4 and M5, only five (11%) M4 cases and three (20%) M5 cases had SL elevations of this magnitude. Lysozyme levels need to be interpreted in conjunction with other parameters for FAB classification.

Effect of prenatal and postnatal exposure to lead on kidney function in male and female rats

The effect of 5 months' exposure to 0.5% lead acetate in drinking water on the kidney function of developing rats was studied. In both sexes, lead exposure produced a significant elevation of the kidney weight and after 3 months' treatment both male and female rats showed signs of tubular impairment. In male rats increased beta 2-microglobulin and lactate dehydrogenase excretion was observed. Lysozyme was increased after 5 months of exposure. No changes were observed in total proteins and albumin excretion. Female rats showed a significantly increased excretion of beta 2-microglobulin from 3 months onwards, while lactate dehydrogenase increased only at the end of 3 months and total proteins after 5 months of exposure. No changes were observed in lysozyme and albumin excretion. Thus, the results suggest that lead exposure produces changes in the renal tubular function of developing rat. There is no sex difference in the nephrotoxicity of lead. Comparison with our previous studies suggests that exposure to lead starting at weaning is more renotoxic than exposure starting 2 months later. However, prenatal exposure might also have been a contributory factor.

Low-molecular-weight (tubular) proteinuria is not related to glycaemic control in non-insulin dependent diabetes mellitus

Early morning urine specimens were obtained from two groups of non-insulin dependent diabetic patients and a group (43 subjects) of normal controls. The diabetic patients were divided into two subgroups according to the degree of diabetic control as judged by their glycosylated haemoglobin (HbA1) levels (well-controlled, 47 subjects; poorly controlled, 51 subjects). The concentration of the low-molecular-weight enzyme (lysozyme) was determined in each urine specimen and related to the concentration of creatinine (lysozyme/creatinine). The mean urinary lysozyme concentration was higher in each of the two diabetic groups as compared with the control group. However, it was not significantly different between the two diabetic groups. These result suggest that there is no association between the degree of glycaemic control and tubular proteinuria.

Direct measurement of renal medullary blood flow in the dog

We studied the responses of total renal blood flow (RBF) and renal medullary blood flow (RMBF) to changes in renal perfusion pressure (RPP) within and below the range of renal autoregulation in the anesthetized dog (n = 7). To measure RMBF, we developed a technique in which the medulla is exposed by excising a section of infarcted cortex and a multiple optical fiber flow probe, connected to a laser-Doppler flowmeter, is placed on the medulla. At the baseline RPP of 120 +/- 1 mmHg, RBF was 2.58 +/- 0.33 ml.min-1.g perfused kidney wt-1, and RMBF was 222 +/- 45 perfusion units. RPP was then decreased in consecutive 20-mmHg steps to 39 +/- 1 mmHg. At 80 +/- 1 mmHg, RBF remained at 89 +/- 4% of the baseline value; however, RMBF had decreased significantly (P < 0.05) to 73 +/- 4% of its baseline value. The efficiency of autoregulation of RBF and of RMBF within the RPP range of 120 to 80 mmHg was determined by calculating an autoregulatory index (AI) for each parameter using the formula AI = (%delta blood flow)/(%delta RPP). An AI of 0 indicates perfect autoregulation, and an index of 1 indicates a system with a fixed resistance. The AI for RBF averaged 0.33 +/- 0.12 over this pressure range and showed a significantly greater (P < 0.05) autoregulatory ability than did the RMBF (0.82 +/- 0.13). Decreasing perfusion pressure < 80 mmHg produced significant decreases in both RBF and RMBF.(ABSTRACT TRUNCATED AT 250 WORDS)

[Urinary enzymes in liver cirrhosis: useful early markers of renal damage?]

Some urinary enzymes (NAG, AAP, lysozyme) considered to be sufficiently sensitive and reliable markers of renal damage were controlled in 20 patients with cirrhosis of the liver and in 20 healthy control subjects. The results, stated as mean +/- SD, showed a statistically very significant increase (p < 0.01) of NAG and lysozyme in cirrhotics. Furthermore, this increase could be at least in part related with the seriousness of clinical condition. On the basis of these results, we think the urinary dosage of NAG and lysozyme is, in the subjects with liver cirrhosis, a bloodless method to show an early renal damage.

Biochemical renal changes in workers exposed to soluble nickel compounds

1. Biochemical markers of kidney damage were examined in 14 male and 12 female workers highly exposed to soluble nickel compounds in a chemical plant. The results were compared to those obtained in 12 male and 12 female matched controls. 2. The concentration of nickel in urine of male and female workers averaged 5.0 and 10.3 micrograms g-1 creatinine, respectively. The mean duration of exposure in male and female workers was 25 and 15 years. 3. No difference was found in the mean urinary excretion of lactate dehydrogenase, albumin and transferrin in both sexes, total proteins, beta 2-microglobulin (beta 2-m) and retinol-binding protein (RBP) in males and lysozyme in females. Lysozyme and N-acetyl-beta-D-glucosaminidase (NAG) were increased in male and total proteins, beta 2-m, NAG and RBP in female exposed workers. Significant correlations between urinary concentrations of nickel on one side and that of beta 2-m in women (r = 0.462, P = 0.022) and men (r = 0.41, P = 0.018) and of NAG in men (r = 0.405, P = 0.019) on the other side were found in exposed subjects. 4. Results indicate adverse effects of soluble nickel compounds on the kidney tubular function. In agreement with literature data it seems that those effects occur only at high exposure levels.

Urinary proteins and enzymes as early indicators of renal dysfunction in chronic exposure to cadmium

We tested the diagnostic sensitivity of various urinary analytes for detecting cadmium-induced nephropathy at an early stage. We investigated 73 healthy persons (control group 1) and individuals exposed to cadmium, either environmentally (n = 36, risk group 2) or occupationally (n = 62, exposed group 3). All data were related to limits of the central 95% reference intervals of the control group. The serum creatinine and ribonuclease values, indicators of the glomerular filtration rate, were not different in the three groups. In the exposed persons (group 3), proximal tubular indicators (low-M(r) proteins lysozyme, ribonuclease, retinol-binding protein, and alpha 1-microglobulin) were more often increased than the glomerular indices (higher-M(r) proteins transferrin, IgG, and albumin). Both the low-M(r) proteins and tubular enzymes were differently altered in their excretion rates. Alanine aminopeptidase, alkaline phosphatase, and N-acetyl-beta-D-glucosaminidase increased even in the risk group 2. alpha 1-Microglobulin was increased in the exposed persons whose cadmium excretion was < 5 mumol/mol creatinine. The combined determination of alpha 1-microglobulin and N-acetyl-beta-D-glucosaminidase exceeded the corresponding upper reference limits in 30% of group 2 and 39% of group 3. We recommend screening for these two analytes to detect cadmium-induced renal dysfunction at an early stage.

Acute (24 hr) toxicity of a combination of four nephrotoxicants in rats compared with the toxicity of the individual compounds

To identify possible hazards of combined exposure to chemicals with the same target organ, a 24-hr single dose experiment was carried out in which the renal toxicity of mercuric chloride, potassium dichromate, d-limonene and hexachloro-1:3-butadiene administered simultaneously was compared with the nephrotoxicity of the individual compounds, using a total of 11 groups each consisting of five 12-wk-old male Wistar rats. The dose levels used were based on the results of a range-finding study with the individual compounds in the same strain of rats kept under similar experimental conditions, and comprised the 'Minimum-Nephrotoxic-Effect Level' (MNEL) and the 'No-Nephrotoxic-Effect Level' (NNEL) of each of the four compounds alone and in combination. A group of vehicle-treated rats served as controls. At the MNEL of the combination, antagonism of effects was encountered, seen for example as less severely increased activity of gamma-glutamyl transferase in the urine. Synergism of effects was also observed, for example increased severity of renal tubular necrosis, and more markedly increased activity of urinary lysozyme, lactate dehydrogenase, alkaline phosphatase and N-acetyl-beta-glucosaminidase. More importantly, however, at the NNEL of the combination no signs of impaired renal function or renal damage were observed, suggesting absence of both dose additivity and potentiating interaction at the tested subeffective levels of the individual nephrotoxicants.

Urinary trehalase activity in chronic glomerulonephritis

To determine the diagnostic role of urinary trehalase in chronic glomerular disease, urinary trehalase activity and other urinary markers such as N-acetyl-beta-D-glucosaminidase (NAG), alanine aminopeptidase (AAP), alkaline phosphatase (ALP), gamma-glutamyltranspeptidase (gamma-GTP), lactate dehydrogenase (LDH), lysozyme and beta 2-microglobulin (BMG) were measured in patients with chronic glomerulonephritis, nephrotic syndrome and chronic renal failure. Urinary trehalase activity was significantly increased in chronic glomerular disease, especially nephrotic syndrome, as compared with that in the healthy subjects. The highest incidence of elevated excretion was observed for trehalase with 52% in chronic glomerular disease, followed by NAG. Urinary trehalase activities in the patients were significantly correlated with the urinary levels of protein, NAG and AAP and total score of tubular damage, but not correlated with urinary levels of BMG or lysozyme. In patients with chronic glomerulonephritis and nephrotic syndrome, there was no significant difference in urinary trehalase activities between with and without hematuria. These results indicate that in some patients with chronic glomerular disease, there is tubular involvement as substantiated by elevation of the other urinary enzymes and BMG. Urinary trehalase is elevated more often in these types of disease than other markers of tubular damage.

Low molecular weight proteins in children with renal disease

Low molecular weight proteins are of interest in children because their increased urinary excretion is a sign of renal tubular disease and their increased plasma concentration is inversely related to glomerular filtration rate. These proteins include beta 2-microglobulin (B2M), retinol-binding protein (RBP), alpha 1-microglobulin (A1M) and lysozyme. B2M is unstable in acid urine, in contrast to RBP and A1M which are more stable. Any increase in the urinary excretion of B2M or RBP is highly specific for tubular disease, whereas increased excretion of A1M may be seen with glomerular proteinuria. Areas of clinical application include tubular and glomerular diseases, detection of drug toxicity, reflux nephropathy, birth asphyxia and insulin-dependent diabetes mellitus. Methods of sample collection and analysis of these proteins are discussed.

Nephrotoxicity of acyclovir and cis-diamminedichloroplatinum(II)--effect of co-administration in rats

The effect of co-administration of acyclovir and cis-diamminedichloroplatinum(II) (cisplatin) on nephrotoxicity in male Wistar rats was investigated. Animals received acyclovir (15 mg/kg body weight, s.c., three times per day for 5 days) or cisplatin (5 mg/kg body weight, i.p., one single injection) or a combination of both drugs. Acyclovir plasma levels were determined after one single acyclovir s.c. injection. Urines were monitored for volume, pH, osmolality and excretion of N-acetyl-beta-D-glucosaminidase (NAG), lysozyme and total protein. Concentrations of blood urea nitrogen and plasma creatinine were determined on day 6. Renal cortical slices were monitored to assess the accumulation of weak organic bases (tetraethylammonium) and acids (p-aminohippurate). Cisplatin induced a marked increase in the excretion of NAG, lysozyme and total protein and an increase in urine volume, plasma creatinine and blood urea nitrogen. Urine osmolality and accumulation of p-aminohippurate were depressed by cisplatin. Acyclovir treatment alone caused no significant symptoms of nephrotoxicity. Co-administration did not impair renal function more than cisplatin treatment alone, excepting a slight rise in lysozyme excretion on day 6. Short-term antiviral therapy with acyclovir, concomitant to cisplatin treatment, may bring, if at all, a slightly increased nephrotoxic risk.

Measurement of lysozyme by an enzyme-linked immunosorbent assay

In this study an enzyme-linked immunosorbent assay has been developed for the determination of lysozyme in saliva, serum and urine. The assay relies on the detection of specific protein rather than lytic activity, a property which has been shown to be most suitable for the quantitation of lysozyme in mucin containing substances. Our results indicate that no pretreatment is necessary for the immunochemical method. The assay is sensitive to concentrations as low as 1 microgram lysozyme/l. The intra-assay and inter-assay coefficients of variation were 5.9% and 15.8% respectively. The lysozyme level in whole saliva was 55.53 +/- 30.35 mg/l, in serum the level was 0.64 +/- 0.15 mg/l and in urine it was 0.17 +/- 0.22 mg/l. Comparisons between immunochemical determination and lytic assays showed a good correlation (serum, r = 0.79, P less than 0.01; saliva, r = 0.85, P less than 0.005; treated saliva, r = 0.96, P less than 0.001).

The protection against gentamicin nephrotoxicity in the streptozotocin-induced diabetic rat is not related to gender

Since gender can influence the renal toxicity of a drug in a given species, the present study was undertaken to evaluate the role of sex in the protection against gentamicin (G)-induced nephrotoxicity afforded by diabetes mellitus (DM) in the rat. We have compared the effects of administration of G (40 mg/kg/day, for 14 days) on male and female DM Sprague-Dawley rats. Non-diabetic animals of both sexes receiving identical doses of G served as controls. At the end of the experiment on day 14, both female (F) and male (M) control groups had similar and marked evidence of nephrotoxicity: elevation of plasma creatinine (F 1.7 +/- 0.7; M 2.8 +/- 0.6 mg/dl), decrease in endogenous 24-h creatinine clearance (Ccr) (F0.3 +/- 0.1; M 0.2 +/- 0.1 ml/min/100 g BW), and histological evidence of severe acute tubular necrosis. In marked contrast, the DM rats showed no functional or morphological evidence of renal damage throughout the study regardless of their gender (day 14: plasma creatinine: F 0.2 +/- 0.03; M 0.2 +/- 0.02; Ccr: F 1.2 +/- 0.1; M 1.6 +/- 0.1 ml/min/100 g BW), and they also accumulated less G in their kidney cortex than the C rats. The male controls exhibited higher renal cortex accumulation of G than the female controls (p < 0.05), whereas the opposite occurred in the DM groups (p < 0.01). Because the validity of using Ccr for the evaluation of GFR changes in experimental nephrotoxicity has been questioned, we have compared, in a separate experiment, three different methods of estimation of GFR (simultaneous short clearances of inulin and Ccr, and 24-h Ccr) in conscious female Sprague-Dawley rats undergoing the same treatment with G described above. At no time during the study did the method used for estimation of the GFR influence the results. We conclude that male and female Sprague-Dawley rats with diabetes are functionally and morphologically equally protected against G. Furthermore, no gender-related differences in the magnitude of G-induced nephrotoxicity was demonstrated in the non-diabetic control animals.

Amelioration of glomerular injury in doxorubicin hydrochloride nephrosis by dimethylthiourea

The hydroxyl radical scavengers dimethylthiourea (DMTU), sodium benzoate, and dimethylsulfoxide (DMSO) were administered to rats before doxorubicin hydrochloride (ADR) (5 mg/kg, IV) to probe the role of free radicals in mediating proteinuria in doxorubicin hydrochloride nephrosis (AN). Because ADR stimulates free radical production, the role of renal glutathione was also evaluated; glutathione metabolism is involved in tissue detoxification processes. DMTU administration to rats with AN caused a significant (p less than 0.01) reduction in their proteinuria after 7 days (52.84 +/- 13.21 mg/24 hours) when they were compared with ADR controls (155.81 +/- 20.16 mg/24 hours). In similar fashion, their urine albumin excretion was also significantly reduced when compared with that of ADR controls (11.13 +/- 2.75 mg/24 hours vs 32.08 +/- 4.14 mg/24 hours; p less than 0.01). DMTU-treated rats also had significantly (p less than 0.001) reduced urinary protein and albumin excretion at 14 days when compared with rats that received ADR alone. The urinary excretion of lysozyme and N-acetyl-glucosaminidase, markers of renal tubular injury, were significantly increased after 7 or 14 days in rats with AN, despite DMTU treatment. Creatinine clearance was significantly reduced (p less than 0.05) in rats receiving ADR alone (0.223 +/- 0.011 ml/min/100 gm) when compared with that in normal controls (0.331 +/- 0.027 ml/min/100 gm) or DMTU-treated rats (0.289 +/- 0.035 ml/min/100 gm). Unlike DMTU, neither sodium benzoate nor DMSO reduced proteinuria in rats with AN.(ABSTRACT TRUNCATED AT 250 WORDS)

Renal tubular protein handling in experimental renal disease

Competitive inhibition of renal tubular transport occurs between low- and high-molecular-weight proteins following intravenous infusion, but this relationship is less clear following de novo glomerular or renal tubular injury. The present study evaluated renal lysozyme and albumin handling following renal tubular injury induced by both low- and high-dose mercuric chloride (0.5 and 2.0 mg/kg) and maleic acid (50 and 400 mg/kg), and following glomerular injury induced by puromycin aminonucleoside (5 mg/100 g) or Adriamycin (5 mg/kg). Subtle renal tubular injury induced only mild isolated albuminuria, while severe tubular injury caused dramatic lysozymuria and moderate albuminuria. However, increased filtration of albumin in these models of glomerular injury did not inhibit lysozyme transport.