I. Franchini

Markers of early renal changes induced by industrial pollutants. II. Application to workers exposed to lead.

The present study has been carried out in the framework of a collaborative research project on the development of new markers of nephrotoxicity. A battery of more than 20 potential indicators of renal changes has been applied to 50 workers exposed to lead (Pb) and 50 control subjects. After application of selection criteria 41 exposed and 41 control workers were eventually retained for the final statistical analysis. The average blood Pb concentration of exposed workers was 480 micrograms/l and their mean duration of exposure was 14 years. The battery of tests included parameters capable of detecting functional deficits (for example, urinary proteins of low or high molecular weight), biochemical alterations (for example, urinary eicosanoids, glycosaminoglycans, sialic acid) or cell damage (for example, urinary tubular antigens or enzymes) at different sites of the nephron or the kidney. The most outstanding effect found in workers exposed to Pb was an interference with the renal synthesis of eicosanoids, resulting in lower urinary excretion of 6-keto-PGF1 alpha and an enhanced excretion of thromboxane (TXB2). The health significance of these biochemical alterations, detectable at low exposure to Pb is unknown. As they were not associated with any sign of renal dysfunction, they may represent reversible biochemical effects or only contribute to the degradation of the renal function from the onset of clinical Pb nephropathy. The urinary excretion of some tubular antigens was also positively associated with duration of exposure to Pb. Another effect of Pb that might deserve further study is a significant increase in urinary sialic acid concentration.

Markers of early renal changes induced by industrial pollutants. I. Application to workers exposed to mercury vapour.

Several markers of renal changes have been measured in a cohort of 50 workers exposed to elemental mercury (Hg) and in 50 control workers. After application of selection criteria 44 exposed and 49 control workers were retained for the final statistical analysis. Exposed workers excreted on average 22 micrograms Hg/g creatinine and their mean duration of exposure was 11 years. Three types of renal markers were studied--namely, functional markers (creatinine and beta 2-microglobulin in serum, urinary proteins of low or high molecular weight); cytotoxicity markers (tubular antigens and enzymes in urine), and biochemical markers (eicosanoids, thromboxane, fibronectin, kallikrein, sialic acid, glycosaminoglycans in urine, red blood cell membrane negative charges). Several bloodborne indicators of polyclonal activation were also measured to test the hypothesis that an immune mechanism might be involved in the renal toxicity of elemental Hg. The main renal changes associated with exposure to Hg were indicative of tubular cytotoxicity (increased leakage of tubular antigens and enzymes in urine) and biochemical alterations (decreased urinary excretion of some eicosanoids and glycosaminoglycans and lowering of urinary pH). The concentrations of anti-DNA antibodies and total immunoglobulin E in serum were also positively associated with the concentration of Hg in urine and in blood respectively. The renal effects were mainly found in workers excreting more than 50 micrograms Hg/g creatinine, which corroborates our previous estimate of the biological threshold of Hg in urine. As these effects, however, were unrelated to the duration of exposure and not accompanied by functional changes (for example, microproteinuria), they may not necessarily represent clinically significant alterations of renal function.

Early indicators of renal damage in workers exposed to organic solvents

SummaryIn order to investigate the renal function, a cross-sectional study was carried out on four groups of workers significantly exposed to a mixture of alicyclic and aliphatic C5-C7 hydrocarbons, to styrene, to a mixture mostly composed of toluene and xylenes and to chlorinated hydrocarbons, respectively. The study involved 438 workers. Exposure was characterized by means of urinary metabolites, or by means of environmental measures, when biological indicators were not available. The renal function impairment indicators included total proteinuria, albuminuria and urinary excretion of muramidase (E.C. 3.2.1.17) and beta-glucuronidase (E.C. 3.2.1.31). The trend of these parameters provides some evidence of renal damage due to occupational exposure to organic solvents and suggests that the lesions are mild and tubular rather than glomerular.

Nephropathies and exposure to perchloroethylene in dry-cleaners

Even in specific risk groups, the relation between exposure to organic solvents and chronic renal diseases remains controversial. Thus, in a collaborative European study, we assessed the renal effects of occupational exposure to perchloroethylene (PCE) in dry-cleaners compared with matched controls who were simultaneously examined. Single high and low molecular weight proteins, kidney-derived antigens and enzymes, and prostanoids were measured in urine. beta 2-microglobulin, creatinine, laminin fragments, and anti-glomerular basement membrane antibodies were also measured in serum. A canonical function based on 23 such variables correctly classified 93% of individuals as either PCE-exposed or controls; with 13 markers, group membership was identified in 87% of subjects. Increased high molecular weight protein in urine was frequently (17/50 vs 1/50, p less than 0.0001) associated with tubular alterations. Changes were consistent with diffuse abnormalities along the nephron in workers exposed to low levels of PCE (median 15 parts per million). Generalised membrane disturbances might account for the increased release of laminin fragments, fibronectin, and glycosaminoglycans, for high molecular weight proteinuria, and for the increased shedding of epithelial membrane components from tubular cells with different location along the nephron (brush-border antigens and Tamm-Horsfall glycoprotein). These findings of early renal changes indicate that solvent-exposed subjects, especially dry-cleaners, need to be monitored for the possible development of chronic renal diseases.

The role of chromium accumulation in the relationship between airborne and urinary chromium in welders

SummaryTwenty-two welders working with high chromium alloyed electrodes have been examined. Biological monitoring of exposure was accompanied by measurement of the hydrosoluble fraction of chromium in the air. Several indices of early renal tubular damage were also determined.The close relationship between airborne and urinary chromium suggests that the urinary excretion of the metal at the end of exposure, and particularly its increase above baseline values, are reliable indicators of absorption rate.The measurement of the renal clearance of diffusible chromium—taken as an index of body burden-showed the influence of the lower exchange rate compartment on the relationship between environmental and urinary chromium. Although the degree of exposure was the same, the urinary excretion of chromium was higher in the workers with a greater chromium body burden.The evaluation of some early nephrotoxicity indicators yielded no dose-effect relationship, even if a more frequent pathological “response” was observed in the subjects with a higher degree of exposure to chromium.

URINARY EXCRETION OF BRUSH-BORDER ANTIGEN REVEALED BY MONOCLONAL ANTIBODY: EARLY INDICATOR OF TOXIC NEPHROPATHY

Mouse monoclonal antibodies against brush-border antigens of the proximal tubule of human kidney were produced by the hybridisation technique. The urinary excretion of a brush-border protein with an apparent molecular weight of 50 000 (BB-50) was measured by a sandwich enzyme-linked immunosorbent assay with a mouse IgG1 against BB-50 and a polyclonal rabbit antiserum against human kidney as coating and second antibodies. The urinary excretion of BB-50 was fifty times higher in patients treated with cisplatin than in a matched control group and twice as high in workers occupationally exposed to water-soluble chromium(VI) compounds as in their matched controls. These findings suggest that the urinary excretion of kidney antigens revealed by monoclonal antibodies is a very sensitive and specific test for the assessment of toxic nephropathies.

Brain dopamine as a target for solvent toxicity: Effects of some monocyclic aromatic hydrocarbons

Adult male rabbits were exposed to toluene, xylene, styrene, ethylbenzene, vinyltoluene or were dosed with hippuric, methylhippuric, mandelic, phenylglyoxylic, and 7-methyl-mandelic acids. Styrene, vinyltoluene and ethylbenzene caused a marked depletion of striatal and tubero-infundibular dopamine. Such an effect was also caused by treatment with mandelic and phenylglyoxylic acids. These results indicate that dopamine is a target for some solvents of their metabolites, the presence of a lateral vinyl- or ethyl-chain which may be biotransformed into alpha-keto acids being crucial for the effect. Experiments in vitro suggest that dopamine condenses non-enzymatically with reactive carbonylic groups of such and other alpha-keto acids, thus becoming ineffective as neurotransmitter. This mechanism might account for the neurobehavioral and neuroendocrine changes which have been reported in workers occupationally exposed to styrene and to some solvent mixtures.

n-Hexane metabolism in occupationally exposed workers.

Lung uptake and excretion of n-hexane were studied in ten workers in a shoe factory. Simultaneous samples of inhaled and alveolar air were collected with the aid of a Rhan-Otis valve, personal samplers, and charcoal tubes. Alveolar excretion was monitored during a six hour postexposure period. Uptake was calculated from lung ventilation, the retention coefficient, and environmental concentrations. The amount of exhaled n-hexane was calculated from the decay curve. According to the experimental data, alveolar retention was about 25% of the inhaled n-hexane, corresponding to a lung uptake of about 17%. The postexposure alveolar excretion was about 10% of the total uptake. The main metabolites of n-hexane were identified and measured by capillary GC/MS in spot urine samples collected before, at the end, and 15 hours after the same working shift. Urinary concentrations were low, though related to n-hexane in the air. 2,5-Hexanedione in the end of shift samples gave the best estimate of overall exposure. About 3 mg/g creatinine of 2,5-hexanedione would correspond to about 50 ppm of n-hexane in the air (mean daily exposure).

Determination of naphthalene metabolites in human urine by liquid chromatography-mass spectrometry with electrospray ionization

The use of a liquid chromatography-electrospray mass spectrometry system was investigated for the quantitative analysis of naphthalene metabolites (alpha-naphthol, alpha-naphthylglucuronide and beta-naphthylsulphate) in untreated urine samples. Chromatography was carried out under ion-suppressed reversed-phase conditions, by using high-speed (3 cm, 3 microns) columns and formic acid (2 mM) as a modifier in the mobile phase. The ionization was obtained in the negative-ion mode. Linearity, sensitivity and precision of the method were explored by operating in selected-ion monitoring mode. The method was applied to the quantitative analysis of naphthalene metabolites in untreated urine samples from workers in a naphthalene producing plant. Solid-phase extraction was used for sample clean-up and trace enrichment. Liquid chromatography-tandem mass spectrometry experiments were performed for confirmation purposes.

Glutathione S-transferases M1-1 and T1-1 as risk modifiers for renal cell cancer associated with occupational exposure to chemicals.

Aims: To investigate the possible interaction between occupational risk factors and genotype for glutathione S-transferases M1 and T1 (GSTM1 and GSTT1) in renal cell cancer (RCC). Methods: One hundred patients with RCC and 200 outpatient controls were enrolled at Parma University Hospital. The polymorphisms of glutathione S-transferase M1-1 (GSTM1) and T1-1 (GSTT1) were investigated by PCR; occupational history was collected by a structured questionnaire. Results: Subjects with GSTM1 present genotype showed higher risks for RCC, compared to GSTM1 null subjects, if exposed to metals (OR 2.73; 95% CI 0.91 to 8.22 v 1.14; 95% CI 0.46 to 2.82) or pesticides (OR 3.46; 95% CI 1.12 to 10.74 v 1.59; 95% CI 0.48 to 5.34). The GSTT1 present genotype also enhanced the risk (about twofold) of RCC among subjects exposed to solvents and pesticides, compared with those GSTT1 null. Conclusions: Results support the hypothesis that GSTM1 and GSTT1 polymorphisms can interact with several occupational exposures to significantly modify the risk of RCC among exposed subjects.