Urinary excretion kinetics of 1-hydroxypyrene in volunteers exposed to pyrene by the oral and dermal route

Two well-informed human volunteers were exposed to 500 micrograms pyrene by ingestion and by dermal application, in two separate experiments. Urinary measurements of 1-hydroxypyrene (1-OHP) were performed on all micturitions taken at intervals of 0.5-4 h for a total period of 48 h after dosing. Following the absorption phase, 1-OHP is excreted with a first order apparent half-life of approximately 12 h for both volunteers and both exposure routes. These results compare well with other previously published studies. A more refined analysis of the data was performed using a two-compartment toxicokinetic model for 'pyrene' (its fraction eventually excreted as 1-OHP). As it was found that a classical first-order system did not adequately fit the data, a non-linear term was introduced in the model for the elimination of urinary 1-OHP. Computer iteration performed on the oral absorption data allowed an estimation of various toxicokinetic parameter values. The mean intercompartmental exchange (k12 and k21) and elimination coefficients were 0.010, 0.006 and 0.012 min-1, respectively. The first two values compare well with those previously published for the rat, whereas the latter is smaller in humans. These values were used to satisfactorily simulate the experimental data for both routes of exposure, adjusting only for kabs which was estimated at 0.014 and 0.0029 min-1 for the oral and dermal exposure, respectively. The proposed model generates new hypotheses on the metabolism of pyrene. The information collected will contribute to the validation of the utilisation of 1-OHP as a biological indicator of exposure to pyrene.

Patterns of 1-hydroxypyrene excretion in volunteers exposed to pyrene by the dermal route

The urinary excretion profiles following exposure to pyrene were established in one psoriasic patient under treatment with a coal tar-based shampoo and in two other volunteers exposed to a single dose of 100 microliters creosote and, in a separate experiment, to five consecutive daily dermal applications of 500 micrograms pyrene on 200 cm2 of the inner face of the forearms. Timed micturitions were collected for up to 48 h following exposure. Both in the psoriasic patient and in the volunteers exposed to creosote, the excretion peaks between 10 and 15 h after application and first-order apparent half lives of 11.5-15 h can be calculated for the elimination phase. Compatible with these observations, repeated exposure to pyrene in the volunteers causes an increase in peak and trough urinary 1-hydroxypyrene (1-OHP) values for the first few days following the first exposure. These results suggest that the difference between beginning-of-shift/beginning of work week and beginning-of-shift/end of work week 1-OHP excretions should reflect the average exposure of the week in workers having a constant exposure to pyrene. The difference between the beginning- and end-of-shift excretion values of a given day should reflect the exposure of that day but the maximum excretion would be attained a few hours after termination of exposure.

Background urinary 1-hydroxypyrene levels in non-occupationally exposed individuals in the Province of Québec, Canada, and comparison with its excretion in workers exposed to PAH mixtures

The urinary excretion of 1-hydroxypyrene (1-OHP) was measured in two reference groups of non-occupationally exposed individuals and in four groups of workers. Two of these groups were exposed to what were considered to be low levels of polycyclic aromatic hydrocarbons (PAH) on the basis that even post-shift 1-OHP excretion values were low (< 2 mumol/mol creatinine). Therefore, urine samples were collected from these workers after a period of > 60 h without occupational exposure which should yield values approaching background levels. Pooling these results with those of the reference groups yielded a total of 140 individuals having a mean (geometric) excretion of 0.08 mumol/mol creatinine and 5th, 50th and 95th percentiles of 0.02, 0.09 and 0.32 mumol/mol creatinine. The mean (geometric) excretion in the 95 nonsmokers and 45 smokers of this pool was 0.07 and 0.12 mumol/mol creatinine, respectively (one-tailed Student t-test, P < 0.001). Both this background excretion and the contribution of smoking appeared small in comparison with the excretion levels observed in some groups of exposed workers. Indeed, creosote workers described in this report had a geometric mean (range) excretion of 1.63 (0.18-10.47) mumol/mol creatinine during their working week. It is concluded that, for the biological monitoring of workers exposed to PAH, urinary 1-OHP appears to be a useful bioindicator for which background environmental contamination or smoking habits can be neglected in most cases.

Kinetics of hemoglobin and albumin adducts in rabbits subchronically exposed to benzo[a]pyrene

Benzo[a]pyrene (BaP) can form adducts with proteins after activation to a diolepoxide. Benzo[a]pyrene-hemoglobin and BaP-albumin adducts were measured in rabbits exposed to 0.5 or 5 mumol.kg-1.week-1 for a total of 11 weeks (last injection on Day 75). Each dose group of nine rabbits was divided into three equal subgroups. For each dose, one subgroup received a single weekly injection (Mondays), the second had two equal weekly injections (Mondays and Thursdays), and the third had five weekly injections (Mondays through Fridays). Blood was collected prior to injection on Days 0, 7, 14, 21, 28, 35, 42, 49, 56, 77, 78, 80, 84, 92, 108, and 140 for adducts determinations, with Day 0 being a Monday. The measured concentration of hemoglobin adducts was independent of the frequency of administration for a given total weekly dose giving support to its value as a "biointegrator." In addition, animals injected with 0.5 and 5 mumol BaP.kg-1.week-1 had respective mean adduct concentrations of 0.3 and 3 pmol/g hemoglobin. The blood concentration of albumin adducts was related to the frequency of injection with the animals receiving one, two and five injections/week having the lowest, intermediate, and highest adduct concentrations, respectively. Animals injected with 0.5 and 5 mumol BaP.kg-1.week-1 had respective mean adduct concentrations of 5 and 20 pmol/g which are 17 and 7 times higher than their corresponding hemoglobin adducts' values. The corresponding albumin adducts' half-lives calculated from the day of cessation of exposure were 5.8 and 9.6 days, compared with a reported 5.7 days for the half-life of the intact protein.(ABSTRACT TRUNCATED AT 250 WORDS)

Chronic nephrotoxicity of soluble nickel in rats

1. Male and female Wistar rats were given 100 mg L-1 of nickel (as nickel sulfate) in drinking water for 6 months. Lactate dehydrogenase, total proteins, N-acetyl-beta-D-glucosaminidase (NAG), albumin and beta 2-microglobulin were measured in 24 h urine after 3 and 6 months of exposure. Body and kidney weights were also recorded. 2. After 6 months, urinary excretion of albumin in control and exposed rats was 354 and 1319 micrograms 24 h-1 for female rats (P < 0.05) and 989 and 2065 micrograms 24 h-1 for male rats (P = non significant). Kidney weights were significantly increased in the exposed groups. No significant changes were observed in other parameters. 3. The results suggest that low-level oral exposure to soluble nickel either induces changes of glomerular permeability in female and possibly in male rats, or enhances the normal age-related glomerular nephritis lesions of ageing rats. The intake was probably not high enough to induce significant tubular changes. The female rat seems to be more sensitive to the nephrotoxic effect of nickel than the male rat.

Improved procedure for the high-performance liquid chromatographic determination of monohydroxylated PAH metabolites in urine

An improved high-performance liquid chromatographic (HPLC) method for the determination of 3-hydroxybenzo(a)pyrene (3-OHBaP) in urine was developed. The sensitivity and reproducibility of the technique was greatly improved by the addition of 1 mg/L ascorbic acid to the methanol eluent of the HPLC system. This procedure also eliminated the peak splitting and band broadening of the 3-OHBaP peak otherwise observed. Furthermore, it corrected the urine matrix effect on the slope of standard curves. In fact, in the absence of ascorbic acid in the HPLC system, slopes of standard curves were steeper when prepared in a methanolic extract of control rat urine (121 L.nmol-1) than in methanol only (86 L.nmol-1). Both these slopes were smaller than that obtained with the modified mobile phase (244 L.nmol-1). The effect of the latter on the shape and intensity of the 1-hydroxypyrene (1-OHP) chromatographic peak was also investigated. Again, slopes were greater when the standards, prepared in a methanolic extract of urine, were chromatographed with ascorbic acid (380 L.nmol-1) than without (157 L.nmol-1). Therefore, it seems that ascorbic acid, like certain substances in urine, may act by masking specific adsorption sites--probably uncapped silanol residues on the LC 18 column that can retain free 3-OHBaP and 1-OHP metabolites.

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.

Kidney function in male and female rats chronically exposed to potassium dichromate

Male and female Wistar rats were given 25 mg l-1 chromium (as potassium dichromate) in drinking water for 6 months. Lactate dehydrogenase, lysozyme, total proteins, N-acetyl-beta-D-glucosaminidase, albumin and beta 2-microglobulin (beta 2-m) were measured in 24-h urine after 3 and 6 months of exposure. Body and kidney weight and chromium excretion were also examined. Except for the chromium excretion, no statistically significant changes were observed in the exposed male rats. In female rats there were significant increases in the urinary excretion of albumin after 3 and 6 months of exposure and the urinary excretion of beta 2-m after 3 months of exposure.

Measurement of hemoglobin and albumin adducts of benzo(a)pyrenediolepoxide and their rate of elimination in the female Sprague-Dawley rat

A high performance liquid chromatographic technique coupled with fluorometric detection was used to study the disappearance rate of the hemoglobin and albumin adducts of benzo(a)pyrene (BaP) in female Sprague-Dawley rats. The technique was considered adequate based on good recovery (> 80%) of the analyte and satisfactory intra-assay coefficients of variations of 7.8% and 4.2% for hemoglobin and albumin adducts, respectively. The persistence of the adducts was determined in rats injected intravenously with 550 nmol BaP diolepoxide, the electrophilic metabolite of BaP. In a first experiment the isolated protein fractions were directly subjected to mild acid hydrolysis to yield the ultimate analyte, BaP tetrol. In a second experiment these fractions were first digested by proteases in order to liberate any unbound lipophilic BaP tetrol possibly "hidden" in the hydrophobic portions of the protein matrices. It was found that 70-100% of the measured tetrols originated from true adducts. The half-life of the free tetrol was 2.8 and 1.6 days in the hemoglobin and albumin fractions, respectively, compared to 10.7 and 3.6 days for the true adducts. Based on the total amount of tetrols, the mean half-life of the latter in the hemoglobin and albumin fractions determined from the two experiments was 9.0 and 2.7 days, respectively, assuming first order kinetics. The greater persistence of the hemoglobin adduct compared to that of the albumin adduct is coherent with the biological half-life of the intact proteins. However, the observed disappearance profile obtained does not fit with current models of adduct formation and removal.

Reversibility of renal tubular dysfunction in streptozotocin-induced diabetes in the rat

Enzymuria and specific proteinuria were examined over a period of 19 days in 4 groups of 5 rats: a control group, a nondiabetic polyuric group, a group of streptozotocin-induced diabetic rats treated with insulin as of the 10th day after the injection of the drug, and a similar group of untreated diabetic rats. Increased urinary excretion of beta-N-acetyl-D-glucosaminidase, lactate dehydrogenase, and alanine aminopeptidase was observed shortly after the induction of diabetes. It was partly or totally reversible following insulin treatment. Nondiabetic polyuria had a slight effect on the excretion of alanine aminopeptidase only. The urinary excretion of beta 2-microglobulin also rapidly increased after the onset of diabetes to a level approximately 50 times the control values. This effect was largely reversible with insulin treatment and was absent in the nondiabetic polyuric group. A small but significant 3-fold increase in albumin excretion was also noted but was not affected by insulin treatment. We conclude that streptozotocin-induced diabetes causes an early tubular dysfunction that is unrelated to polyuria and is reversible upon insulin treatment. This tubular dysfunction is best revealed by the urinary excretion of the low molecular weight protein beta 2-microglobulin. Our results suggest that it would be of interest to further examine the usefulness of sensitive markers of tubular dysfunction, especially low molecular weight proteinuria, in the detection of early stages of diabetic nephropathy.

Enzymuria and tubular proteinuria in diabetic rats: a 12-week follow-up study

Various biochemical parameters of renal tubular function were examined for a period of up to 12 weeks in rats rendered diabetic by an i.v. injection of streptozotocin. Except for a statistically significant decrease in the urinary excretion of gamma-glutamyl-transpeptidase to 64% of control values, the urinary excretion of beta-N-acetyl-D-glucosaminidase, beta-galactosidase, alanine aminopeptidase, and lactate dehydrogenase significantly increases in diabetic rats to between 154% and 712% of control values. This increased enzymuria is not correlated to the marked polyuria induced by diabetes (r between 0.14 and 0.35, not significant). Enzymuria is also accompanied by a 10-fold increase in the urinary excretion of the low molecular weight protein beta 2-microglobulin while the excretion of albumin is not significantly modified, indicating impairment of tubular reabsorption in diabetic animals. Clearance studies reveal that the clearance of both beta 2-microglobulin and infused egg-white lysozyme are also increased. Finally the histopathologic examination of paraffin sections of the kidney show hydropic degenerescence and pycnosis of the tubular cells. It is concluded that early-stage diabetes results in tubular impairment and that the streptozotocin-rat model appears well suited to the study of these early signs of renal dysfunction.

Male rat specific nephrotoxicity resulting from subchronic administration of hexachlorobenzene

Male rats are more sensitive to the nephrocarcinogenic effect of hexachlorobenzene (HCB) than are female rats. The purpose of this study was to shed light on this phenomenon by investigating mechanisms of subchronic nephrotoxicity of HCB. Groups of rats were administered HCB in corn oil (po) at 100 mg/kg, 5 days per week for 15 days or at 50 mg/kg, 5 days per week for 50 days. Urine was collected on Days 1, 8, and 15 for the 15-day treatment and on Day 50 for the 50-day treatment. Glucosuria, proteinuria, and enzymuria (gamma-glutamyl transpeptidase) were measured to assess renal function. Twenty-four hours after the last HCB treatment, the animals were killed and kidneys were removed for histopathological evaluation. Urine analyses showed no indication of renal dysfunction in treated animals compared to controls during the 15-day treatment. However, histology of male rat kidneys revealed degenerative and regenerative cellular foci accompanied by an increased accumulation of protein droplets in epithelial cells of the proximal tubules. The same histological observations were also made in male rats after a 50-day HCB treatment but this time they were accompanied by renal function alterations. In female rats, no such renal functional or histological alterations were observed. The histopathological observations in male rats correspond well with the protein droplet nephropathy; the latter is characteristic of the accumulation in kidney cells of alpha 2u-globulin probably caused by the reversible binding of a chemical to alpha 2u that renders the protein indigestible to kidney proteases. alpha 2u-Globulin was measured in the cytosol of male rats and was found to be increased 11-fold compared to controls. Also, HCB was found to be bound reversibly to alpha 2u. These results suggest that HCB induces a male rat specific nephropathy that could explain the higher incidence of kidney tumors in male rats compared to female rats.

Aviation gasoline: comparative subchronic nephrotoxicity study in the male rat

Biochemical and histopathologic parameters of nephrotoxicity were measured in groups of male Fischer-344 rats after a 2-week, 5-days-a-week schedule of oral administration (0.5 ml/kg) of the following substances: aviation gasoline (grade 100) (AVG), automobile regular unleaded gasoline (ULG) and 2,2,4-trimethylpentane (TMP). Results of renal histopathologic examinations and biochemical parameters were compatible with the following order of increasing nephrotoxicity: ULG less than TMP less than AVG. The high nephrotoxic potential of aviation gasoline may be related to its elevated content in branched hydrocarbons.

The renal uptake of proteins: a nonselective process in conscious rats

The selectivity of the renal reabsorption of proteins has been investigated by competition experiments in conscious rats. The animals were intravenously injected with increasing doses of proteins over a wide range of net charge and size, including lysozyme, cytochrome C, metallothionein, beta 2-microglobulin, retinol-binding protein, albumin and IgG. The urinary excretion of exogenous proteins injected concomitantly (human beta 2-microglobulin, retinol-binding protein, albumin and/or egg white lysozyme depending on the experiment) and of rat beta 2-microglobulin, albumin and IgG was determined with specific immunoassays. The results show that low molecular weight cationic proteins and low or high molecular weight anionic proteins can increase each other's urinary excretion. Several observations strongly suggest that these effects result from a competitive inhibition of renal uptake. The phenomenon is dose-related in most cases and, as evidenced by cytochrome C injection, transient, reproducible and saturable. In addition, the injected proteins induce a tubular type proteinuria irrespective of their net charge and size. In the case of cationic proteins, this finding excludes the possibility of an enhanced glomerular permeability due to a partial neutralization of the glomerular polyanion which, as demonstrated with protamine sulfate, entails a glomerular type proteinuria. These quantitative data on the mutual inhibition of renal uptake of a wide spectrum of specific proteins lead us to challenge the concept of charge- and size-selective tubular reabsorption of proteins, and to postulate that proteins filtered through the glomeruli are taken up by common tubular endocytotic sites irrespectively of their physicochemical features. As demonstrated by the ability of beta 2-microglobulin and IgG to inhibit the uptake of lysozyme, the affinity of a protein for reabsorption sites is not simply related to its size and net positive charge. Evidence is also presented that proteins, when administered intravenously at high doses, induce a lysosomal enzymuria most likely reflecting a stimulated exocytosis.

Evaluation of the nephrotoxic potential of styrene in man and in rat

The urinary excretion of beta 2-microglobulin, retinol-binding protein and albumin was measured in 65 workers exposed to styrene at levels averaging 50 percent of the current threshold limit value (215 mg/m2) for 1-13 years (mean: 6 years). By comparison with a control group matched for age and socioeconomic status, no significant difference was observed in the urinary excretion of proteins. In rats, styrene was weakly nephrotoxic. No functional or morphological renal change could be disclosed in rats exposed to 565 mg of styrene/m3, 5 days/week for 13 weeks. The repeated i.p. injection of 1 g styrene/kg (1/5 of oral LD50) for 10 days induced only a slight tubular dysfunction as evidenced by a 5-fold increase in beta 2-microglobulinuria. Altogether, these epidemiological and experimental data suggest that the current threshold limit value for styrene (215 mg/m3) proposed by the American Conference of Governmental and Industrial Hygienists does not entail any risk of renal toxicity.

Determination of IgE complexes and of total IgE by latex immunoassay

A sensitive immunoassay based on latex particle agglutination for the measurement of circulating IgE-containing complexes is described. In this method, the anti-IgE-coated particles are incubated with diluted serum and the resulting agglutination is quantified by turbidimetry or particle counting. In the latter version, the assay is fully automated in a continuous flow system. IgE-containing complexes were detected in all tested sera. Increased concentrations were observed in about 80% of the subjects with elevated serum IgE. However, high levels of IgE-complexes may also be found in subjects with a normal or even a very low serum concentration of IgE. The same latex immunoassay can be used for the determination of total IgE, after pepsin digestion of the gamma-globulin fraction of the serum. The results obtained correlate well with those found with a sandwich radioimmunoassay (r = 0.91, n = 83). The present method, however, yields a greater number of significantly positive results than the radioimmunoassay, probably because of its ability to detect IgE entrapped in circulating complexes.

A cross-sectional survey of kidney function in refinery employees

We examined sensitive biochemical and immunological markers of kidney function and damage in 53 male oil refinery workers exposed to hydrocarbons and compared their results with those of a control group of 61 age-matched nonexposed males. The mean duration of employment of exposed males was 11 years. The current levels of exposure to a variety of aliphatic and aromatic hydrocarbons, as determined by personal monitoring, were well below the current threshold limit values. No difference was found in the urinary tubular parameters beta-N-acetyl-D-glucosaminidase, beta 2-microglobulin (beta 2-m) and retinol-binding protein. Similar serum beta 2-m levels indicated no impairment of the glomerular filtration rate in the exposed workers. The levels of circulating immune complexes were also identical in both groups. The mean albuminuria was slightly higher (p less than .005) in the exposed group in a quantitative assay but was not dipstick-detectable. The mean urinary excretion of a renal antigen was also higher (p less than .05) in the exposed group and correlated with the excretion of albumin. Finally, slightly higher titers of anti-laminin antibodies were found in five exposed employees, but this was not accompanied by an increased albuminuria. We conclude that chronic low-level hydrocarbon exposure in these refinery workers does not lead to clinically significant renal abnormalities. Nevertheless, some findings are consistent with the possible role of hydrocarbon exposure in the induction of renal disturbances.

Competition between low- and high-molecular-weight proteins for renal tubular uptake

To explain the occurrence of tubular and glomerular proteinuria in patients with primarily tubular or glomerular dysfunction, it is usually assumed that the mechanisms responsible for the renal tubular transport of small and large proteins are different. The present in vivo study does not support this hypothesis since it clearly shows that small and large proteins (e.g., beta 2-microglobulin and albumin) can compete for renal uptake. Our results lead us to postulate the existence of common tubular reabsorption sites for which proteins exhibit different affinities depending on their charge, size and conformation.

Detection of anti-laminin antibodies in sera by latex agglutination

We describe a latex particle agglutination assay for detecting circulating antibodies against laminin, a noncollagenous glycoprotein of basement membranes. Polystyrene latex particles on which laminin has been adsorbed are incubated with serum for about 25 min at 42-45 degrees C. The agglutination is then measured by counting residual unagglutinated particles. Polyethylene glycol 6000 enhances the agglutination. The assay is fully automated, yielding results in about 45 min, for 50 samples per hour. Addition of purified laminin abolishes the agglutination of laminin-coated particles in practically all positive sera. The anti-laminin antibody titers obtained by this latex immunoassay and by radioimmunoassay correlated well in 161 sera from patients with suspected or established renal diseases. The agglutination assay more frequently gave positive results for cases of glomerulonephritis with linear deposits (20/22 cases) than for glomerulonephritis with granular deposits (7/68) or glomerulonephritis with no glomerular deposits (2/13). The finding of low anti-laminin antibody titers in sera from about 15% (34/230) of the healthy subjects suggests that these autoantibodies are pathogenic only in certain circumstances.

Detection of anti-laminin antibodies in sera by latex agglutination

We describe a latex particle agglutination assay for detecting circulating antibodies against laminin, a noncollagenous glycoprotein of basement membranes. Polystyrene latex particles on which laminin has been adsorbed are incubated with serum for about 25 min at 42-45 degrees C. The agglutination is then measured by counting residual unagglutinated particles. Polyethylene glycol 6000 enhances the agglutination. The assay is fully automated, yielding results in about 45 min, for 50 samples per hour. Addition of purified laminin abolishes the agglutination of laminin-coated particles in practically all positive sera. The anti-laminin antibody titers obtained by this latex immunoassay and by radioimmunoassay correlated well in 161 sera from patients with suspected or established renal diseases. The agglutination assay more frequently gave positive results for cases of glomerulonephritis with linear deposits (20/22 cases) than for glomerulonephritis with granular deposits (7/68) or glomerulonephritis with no glomerular deposits (2/13). The finding of low anti-laminin antibody titers in sera from about 15% (34/230) of the healthy subjects suggests that these autoantibodies are pathogenic only in certain circumstances.

Effects of gentamicin on the renal uptake of endogenous and exogenous protein in conscious rats

To study the effect of gentamicin on the renal uptake of proteins, Sprague-Dawley female rats were intravenously injected with solutions containing unlabeled human beta 2-microglobulin (beta 2-m), retinol-binding protein, and increasing amounts of gentamicin (from 0.063 up to 31.5 mg/kg). The concentrations of human proteins and that of endogenous beta 2-m, albumin, and IgG in the urine collected during the 2 hr following the injection were determined by immunoassays. Gentamicin transiently increased the urinary excretion of rat and human beta 2-m in a dose-dependent manner. The mean relative increase of rat beta 2-m excretion ranged from 2 at a gentamicin dose of 0.06 mg/kg up to 500 at a gentamicin dose of 31.5 mg/kg. By contrast, the urinary excretion of other proteins was only increased by a factor of 2 to 5 at the highest dose of gentamicin. The relative increase of the urinary excretion of proteins was positively correlated with the fractional reabsorption of the proteins by the rat kidney. The inhibitory effect of gentamicin on the renal uptake of protein was very similar to that observed in rats injected with polycationic proteins like lysozyme and cytochrome C. These observations, combined with the fact that gentamicin, like proteins, enters the tubular cell by adsorptive endocytosis, strongly suggest that this drug competes with proteins for common binding sites on the apical tubular membrane and for subsequent endocytosis. Furthermore, the iv injection of large amounts of gentamicin and polycationic proteins induces a lysosomal enzymuria which very likely is a manifestation of an increased exocytosis.

Determination of rat beta 2-microglobulin in urine and in serum. I. Development of an immunoassay based on latex particles agglutination

Rat beta 2-microglobulin has been isolated from the urine of rats pretreated with sodium chromate. The purified protein was used to raise antisera in two rabbits. Treatment of the antisera with ammonium sulphate followed by gel chromatography led to an immunoglobulin fraction which was used to coat latex particles by physical adsorption. The latex suspension was used in an automated system including an optical particle counter to analyse the protein in serum, urine and cerebrospinal fluid. Serum contains 5.8 mg of beta 2-microglobulin/l, of which 33% is found as a 55000 dalton complex while 66% is present as the 'free' protein. The daily urinary excretion of beta 2-microglobulin in females is about 2 micrograms of which 7% is found to be a 65000-dalton complex while 92% is the free protein. From this, it can be calculated that the fractional urinary excretion of beta 2-microglobulin is about 0.03%. The cerebrospinal fluid contains about 1 mg of beta 2-microglobulin/l. Preliminary tests also suggest that the method can be adapted for non-automated turbidimetric detection. In the automated assay, the within- and between-assay coefficients of variation are less than 10% for the three biological fluids tested. The analytical recovery in the urine is 93%. In urine, beta 2-microglobulin undergoes proteolytic degradation at pH below 6. This does not represent a serious drawback to its use as a sensitive index of tubular function since in most experimental circumstances, rats excrete urine with a pH above this value.

Determination of rat beta 2-microglobulin in urine and in serum. II. Application of its urinary measurement to selected nephrotoxicity models

beta 2-microglobulin (beta 2-m) was measured in the urine of rats by a specific immunoassay based on latex particles agglutination. The excretion of this protein was compared to the excretion of the enzyme beta-N-acetyl-D-glucosaminidase (NAG), albumin and amino acids in rats treated with either a single dose of sodium chromate (5 and 10 mg kg-1), repeated doses of gentamicin (5 and 20 mg kg-1), or cadmium (1 mg kg-1), and in aging rats (from 2 to 20 months). All treatments resulted in an early increased excretion of beta 2-m indicative of functional alterations of the proximal tubular cells. An increased NAG excretion was observed only at the highest dose of chromate and in the cadmium model but the relative increases of beta 2-m were much larger (up to 200 times the control values against four times the control values for NAG). From 2 to 20 months of age, urinary beta 2-m increases by a factor of four. Aminoacids excretion showed little sensitivity in the various models. Albumin showed little variations in purely tubular or in the tubular phase of renal injury but the chronic progressive nephrosis of aging rats caused a 40-fold increase in its excretion between 2 and 20 months of age. Therefore urinary beta 2-m, albumin and albumin/beta 2-m ratio provide useful tools in the assessment of nephrotoxicity and of its mechanisms in various experimental models.

Isoparaffinic solvent-induced nephrotoxicity in the rat

Prolonged inhalation exposure to 6.5 mg/l of an isoparaffinic solvent consisting of saturated aliphatic hydrocarbons (SAHC) resulted in both functional and morphological renal changes in male rats to the exclusion of female or castrated rats. Functionally, the increased excretion of lactate dehydrogenase in the absence of an increased beta-N-acetyl-D-glucosaminidase excretion together with a decreased urinary concentrating ability upon water deprivation and slower antinatriuretic response when the sodium intake is abruptly reduced, suggest a distal tubular alteration. beta 2-Microglobulin excretion is unchanged indicating good proximal tubular cell function. The increased excretion of albumin and slightly lowered glomerular filtration rate suggest a moderate glomerular impairment. Light microscopy shows prominent hyaline droplet accumulation in proximal tubular cells and a few scattered foci of regenerative epithelia in both proximal and distal cells of the deep cortex. The urinary clearance of the major male rat urinary protein, alpha 2u-globulin, is similar in control and exposed rats but the latter have a 10-fold greater renal accumulation of this protein while the hepatic levels are identical in both groups. It is concluded that SAHC exposure causes moderate and reversible tubular and also glomerular changes in the male rat kidney.

Cadmium, analgesics, and the chronic progressive nephrosis in the female Sprague-Dawley rat

Female Sprague-Dawley rats received phenacetin or aspirin at average daily doses of 135 and 27 mg/kg respectively in the diet and either demineralized water (DMW) or a 100 ppm cadmium (Cd) solution as their drinking water for 12 months. This dose of Cd produced borderline tubular toxicity, as measured by the excretion of IV-injected human beta 2-microglobulin. The kidney accumulation of Cd just reached the critical level of 200 ppm in all groups at the end of the study. The various treatments did not significantly affect growth, creatinine clearance, urine osmolality and the urinary excretion of beta-N-acetyl-D-glucosaminidase and aminoacids. No interaction resulted from the concomitant administration of analgesics and Cd. Both aspirin subgroups (receiving DMW or Cd) showed an attenuation of the age-related decline of the renal function as revealed by a lower urinary excretion of albumin and total protein. The accentuation of the mesangial matrix seen upon aging was also partly inhibited in the aspirin rats.

Distal tubular dysfunction in rats chronically exposed to a 'white spirit' solvent

Inhalation exposure of male Sprague-Dawley rats to an industrial white-spirit solvent composed of a C10-C12 mixture of branched-chain unsubstituted satured aliphatic hydrocarbons at 6500 mg/m3 for over 9 months resulted in decreased urinary concentrating ability, decreased net acid excretion following a mild ammonium chloride load and increased urinary lactate dehydrogenase (LDH) activity, whereas urinary beta-N-acetyl-D-glycosaminidase (NAG) activity remained normal. These observations suggest the existence of distal tubular alteration in the rat kidney.

Characterization of cadmium proteinuria in man and rat

In workers chronically exposed to cadmium and without signs of renal insufficiency, plasma proteins with molecular weight ranging from 11,800 to 450,000 are excreted in greater amount in urine. Increased urinary excretion of low and high molecular weight proteins can occur independently. Because of its greater stability in urine and provided a sensitive immunological technique is used, the determination of retinol-binding protein is a more practical and reliable test of proximal tubular function than beta 2-microglobulin. The evaluation of renal function of workers removed from cadmium exposure indicates that cadmium-induced renal lesions, albeit of slow progression, are not reversible when exposures ceases. In workers chronically exposed to cadmium or removed from cadmium exposure, metallothionein in urine is directly correlated with cadmium in urine but not with cadmium in blood or years of cadmium exposure. The association between cadmium in urine and metallothionein in urine is independent of the status of renal function and the intensity of current exposure to cadmium. Whereas the repeated IP injection of high doses of cadmium to rat gives rise to a mixed or tubular type proteinuria, the prolonged oral administration of cadmium results mainly in the development of a glomerular type proteinuria. The former is usually reversible after cessation of treatment whereas the latter is not. Circulating antiglomerular basement membrane antibodies have been found in man and in rat chronically exposed to cadmium. The pathogenic significance of this finding deserves further investigation.

Renal handling of human beta 2-microglobulin in normal and cadmium-poisoned rats

The renal handling of human beta 2-microglobulin (beta 2-m) was investigated in normal rat and in rat with cadmium-induced renal damage. Cadmium was administered either in drinking water at a concentration of 100 ppm for up to 16 months or by i.p. injection of 1 mg Cd/kg, five times a week for up to 4 months. When renal dysfunction has developed, namely after 2 and 10 months of the i.p. and oral treatment respectively, unlabelled human beta 2-m was injected intravenously and its disappearance in serum and its urinary excretion were studied by means of a sensitive immunoassay. In serum, the level of beta 2-m drops by about 90% during the 10 first min, then declines more slowly with a half life around 20 min. Serum disappearance curves of beta 2-m in normal and cadmium-treated rats did not differ markedly. The amount of beta 2-m recovered in urine during the 4 h following the injection averaged 0.03% of the injected dose in normal rats. It increased on the average to 10% in rats treated i.p. with 1 mg Cd/kg for 3 months. However, in rats given 100 ppm Cd per os for 10 months, this amount averaged only 0.14%. A similar value was observed 5 months later, although at that stage, the critical level of cadmium in kidney cortex had been reached for 6-7 months. These data which were in accordance with the disturbances of the other renal parameters measured in cadmium-treated rats indicate that: 1) human beta 2-m is reabsorbed by rat kidney at a similar rate as by human kidney; 2) if the occurrence of cadmium tubulopathy is concomitant with the saturation of cadmium-binding sites in kidney, its severity depends greatly on the rate at which cadmium reaches the saturated kidneys.

Gentamicin nephrotoxicity in cadmium, lead and mercury pretreated rats

The effect of a previous chronic exposure to cadmium, lead or inorganic mercury on the nephrotoxic potential of gentamicin was investigated in female Sprague-Dawley rats. A daily dose of 10 mg gentamicin/kg body weight/day was administered for 21 days to rats having a renal load of 168 micrograms Cd, 35 micrograms Pb or 129 micrograms Hg/g whole kidney. Urine analysis suggests an attenuation of the nephrotoxic potential of gentamicin while a microscopical examination of kidneys indicates a superimposition of the effects of the metals and the antibiotics. The only clear interaction observed consists in a reduction of gentamicin accumulation in the cortex of cadmium-treated animals. It is concluded that none of the metal pretreatments potentiates the nephrotoxic effects of gentamicin.