[Evaluation of the advantage of determination of urinary pseudouridine for the early detection of a malignant transformation process]

The catabolism of tRNA gives rise to modified nucleosides, among which pseudouridine, which are excreted in urine. An increased cell turnover is associated with an enhanced excretion of these products. Some authors have also reported an increased urinary excretion of pseudouridine in asbestos workers without clinical signs of malignancy. In two experimental models of carcinogenesis (i.e. injection of Lewis carcinoma cells in C57/B1C mice and oral administration of 7,12 dimethyl-benz(a)anthracene in female Sprague-Dawley rats), we have confirmed that the occurrence of the tumor is associated with an increased urinary excretion of pseudouridine. This metabolic change, however, does not precede the detection of the tumor. In control human subject, no sex and age effect was found in the urinary concentration of pseudouridine. Patients with a malignant disease excrete an enhanced amount of pseudouridine. A pilot study among workers exposed to polycyclic aromatic hydrocarbons in a coke oven did not reveal any change in the urinary concentration of pseudouridine.

Renal effects of cadmium body burden of the general population

In a cross-sectional population study to assess whether environmental exposure to cadmium is associated with renal dysfunction, 1699 subjects aged 20-80 years were studied as a random sample of four areas of Belgium with varying degrees of cadmium pollution. After standardisation for several possible confounding factors, five variables (urinary excretion of retinol-binding protein, N-acetyl-beta-glucosaminidase, beta 2-microglobulin, aminoacids, and calcium) were significantly associated with the urinary excretion of cadmium (as a marker of cadmium body burden), suggesting the presence of tubular dysfunction. There was a 10% probability of values of these variables being abnormal when cadmium excretion exceeded 2-4 micrograms/24 h. Excretion reached this threshold in 10% of non-smokers. There was also evidence that diabetic patients may be more susceptible to the toxic effect of cadmium on the renal proximal tubule.

Health effects of environmental exposure to cadmium: objectives, design and organization of the Cadmibel Study: a cross-sectional morbidity study carried out in Belgium from 1985 to 1989

Cadmium is a cumulative environmental pollutant. For the general population mainly exposed by the oral route and through tobacco smoke inhalation, the kidney is the critical organ. Belgium is the principal producer of cadmium in Europe, and certain areas of the country are polluted by cadmium mainly because of past emissions from nonferrous industries. Preliminary studies carried out in one polluted area have suggested that environmental pollution might lead to an increased uptake of cadmium by the human body and possibly to health effects. Thus, a large-scale morbidity study has been initiated to assess the validity of this hypothesis. The present paper describes the protocol of this study. Its main objectives are to determine to what extent environmental exposure to cadmium resulting from industrial emissions may lead to accumulation of the metal in the human organism; to establish whether or not environmental exposure may induce renal changes and/or influence blood pressure; and to assess the acceptable internal dose of cadmium for the general population. The study design takes advantage of the fact that biological indicators of exposure, body burden, and early nephrotoxic effects of cadmium are available, which increase the likelihood of detecting a cause-effect relationship.

Inorganic arsenic methylation by rat tissue slices

Rat liver, kidney and lung slices methylate trivalent inorganic arsenic (AsIII) to monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA); the liver has the greatest methylating capacity. AsIII enters the liver cells by a diffusion process followed by extensive binding to intracellular components which favors its extensive accumulation inside the cells. Reduced glutathione regulates AsIII metabolism through several mechanisms: facilitation of AsIII diffusion into the cells, stimulation of the first methylation reaction and increase of DMA excretion by the cells. An excess of AsIII inhibits DMA production by liver cells but this inhibition is reversible; mercuric ions inhibit both MMA and DMA production probably by decreasing inorganic arsenic (Asi) uptake and the second methylation reaction. DMA can be produced from MMA by rat liver slices and this methylation step is stimulated by GSH. In contrast to AsIII, AsV is not extensively taken up by the hepatocyte and is thus poorly methylated.

Urinary kallikrein activity in workers exposed to cadmium, lead, or mercury vapour

A significant reduction of kallikrein activity in urine (assayed by its amidolytic activity) was found in 64 normotensive workers who had been exposed to cadmium for 11 years on average and whose cadmium concentrations in urine ranged from 2.2 to 33.1 micrograms/g creatinine. The mean (geometric) urinary kallikrein activity (in U/g creatinine) amounted to 0.52 (range 0.11-1.90) in the control group (n = 193) against 0.39 (range 0.10-1.03) in the cadmium group, and the prevalence of abnormally low activity levels (less than or equal to 0.20 U/g creatinine) amounted to 17.2% in the cadmium group against 5.2% in the control group. A reduction of aldosterone release (aldosterone in urine) associated with an increased natriuresis was also observed. This might constitute a compensatory mechanism maintaining blood pressure in the normal range. These biological effects of cadmium were not reversible after removal from exposure. This study indicates that cadmium can induce an irreversible toxic effect in the distal nephron. It also suggests that an excessive cadmium body burden alone may not be sufficient to induce hypertension, but in individuals whose blood pressure regulation may be impaired by other factors cadmium could stimulate the development of hypertension. This study also supports the recommendation to prevent hypertensive subjects from being exposed to cadmium. There was no indication that moderate exposure to mercury vapour (n = 53; mercury in urine, range 11-224 micrograms/g creatinine; average duration of exposure: six years) or to inorganic lead (n = 23; lead in blood, range 40-67 micrograms/100 ml; average duration of exposure: eight years) was associated with a reduction of kallikrein production by the kidney.

Cellular metabolism of arsenic studied in mammalian cellsin vitro

The cytotoxicity of trivalent and pentavalent inorganic arsenic was studied in cultured mouse fibroblasts. Concentrations of As(III) in the μM range and approximately 10-fold higher concentrations of As(V) led to a reduction of cellular proliferation and viability with a concomitant increase of LDH release and stimulation of lactate production. Cells pretreated with a low As(III) concentration were less sensitive to toxic doses of As(III) or As(V).Uptake of As(III) by the cells was greater than that of As(V). Both forms of inorganic arsenic were converted intracellularly to monomethylarsonic (MMA) and dimethylarsinic (DMA) acids, which were subsequently released into the culture medium. In As-pretreated cells, which proved more resistant to As toxicity, biotransformation of inorganic to MMA and DMA was increased.

Health significance of cadmium induced renal dysfunction: a five year follow up

To assess the health significance of the early renal changes after chronic exposure to cadmium, 23 workers removed from exposure because of the discovery of an increased urinary excretion of beta 2-microglobulin or retinol binding protein, or both, have been examined once a year for five years. Eight of these workers had also an increased albuminuria. These workers had been exposed to cadmium for six to 41.7 years (mean 25 years) and their first follow up examination took place when they had been removed from exposure for six years on average. At that time, their mean age was 58.6 years (range: 45.5-68.1). It has been confirmed that the proteinuria induced by cadmium is irreversible. The most important finding, however, is a significant increase of creatinine and beta 2-microglobulin concentrations in serum with time, indicating a progressive reduction of the glomerular filtration rate despite removal from exposure. It is estimated that on average this rate has decreased by 31 ml/min/1.73 m2 during the five year follow up study. This decrease is significantly greater (about five times) than that accounted for by aging and is not more pronounced in workers with impaired renal function at the start of the study than in those presenting only with subclinical signs of renal damage. Serum alkaline phosphatase activity also increases significantly with time. In conclusion, the present study indicates that the early renal changes induced by cadmium should be regarded as adverse effects; they are predictive of an exacerbation of the age related decline of the glomerular filtration rate.

Influence of 2,3-dimercaptopropane-1-sulfonate and dimercaptosuccinic acid on the mobilization of mercury from tissues of rats pretreated with mercuric chloride, phenylmercury acetate or mercury vapors

The efficiency of the sodium salt of 2,3-dimercaptopropanesulfonic acid (DMPS) and meso-dimercaptosuccinic acid (DMSA) to mobilize mercury from tissues has been assessed in rats pretreated with different doses of HgCl2, phenylmercury acetate or exposed to different concentrations of mercury vapors. These pretreatments increase the mercury concentration in the kidney and to a lower extent in the liver. Only exposure to metallic mercury vapor leads to mercury accumulation in the brain. Both chelators mobilize mercury stored in the kidney and the amount of metal excreted in urine following a single administration of DMSA is a good indicator of the renal burden of mercury. The rate of removal is greater after DMPS administration than after DMSA but repeated administration of either agents eventually leads to the same total amount of mercury mobilized from the kidney. The loss of mercury from the liver can be slightly accelerated by repeated administration of the chelators. However, the chelators are inefficient in removing mercury from the brain.

Role of thiols in the in-vitro methylation of inorganic arsenic by rat liver cytosol

Rat liver cytosol inactivates inorganic arsenic (Asi) through methylation; S-adenosylmethionine is the methyl group donor and reduced glutathione (GSH) is required for full activity. The study of the combined effects of Asi, GSH and other thiols in vitro and the results of our previous in-vivo studies in humans and rats are consistent with a pathway involving the formation of a monomethylated metabolite which is either rapidly further methylated into a dimethylated derivative or is spontaneously oxidized into monomethylarsonic acid (MMA). The dimethylated metabolite gives rise to dimethylarsinic acid. The first methylation reaction is rate limiting, can be stimulated by GSH and is catalyzed by an enzyme different from that which transfers the second methyl group. The latter is sensitive to inhibition by inorganic arsenic. The stimulation of the first methylation reaction by GSH can only be evidenced at high Asi concentration because under these conditions, the second methylating enzyme can be sufficiently inhibited by Asi to allow some accumulation of MMA. The latter may also slow down the first methylation reaction. A large excess of thiol groups may prevent the methylation reactions probably by decreasing the amount of free trivalent arsenic.

Study of factors influencing the in vivo methylation of inorganic arsenic in rats

Previous studies have shown that several factors may influence the methylation of inorganic arsenic by rat liver in vitro (Buchet and Lauwerys, 1985). The present study attempts to assess the relevance of these observations in vivo. Like man, rat inactivates inorganic arsenic by methylation to monomethylarsonic (MMA) and dimethylarsinic (DMA) acids which are excreted in urine along with unchanged inorganic arsenic (Asi). The administration of S-adenosylmethionine alone or in association with reduced (GSH) or oxidized glutathione or acetylcysteine and the increase of hepatic GSH level by butylated hydroxytoluene pretreatment do not stimulate the urinary excretion of the methylated arsenic metabolites following a challenge dose of inorganic arsenic. Conversely a reduction of the hepatic GSH level by phorone pretreatment greatly modifies the metabolism of inorganic arsenic in vivo. A reduction exceeding 90% of the control value leads to a decreased urinary excretion of MMA and DMA and an increased urinary excretion of inorganic arsenic. This is also associated with an increased accumulation of inorganic arsenic in the liver. This suggests that a drastic reduction of GSH level in liver not only impairs the methylation of inorganic arsenic but also impairs its biliary excretion. When GSH depletion is less severe, the total amount of arsenic excreted in urine after a challenge dose of NaAsO2 is not significantly different from that found in unpretreated animals but the proportion of the three metabolic forms is different: MMA is reduced whereas Asi and DMA tend to increase. These changes resemble those found in patients with liver insufficiency (J.P. Buchet, A. Geubel, S. Pauwels, P. Mahieu, and R. Lauwerys (1984). The influence of liver disease on the methylation of arsenite in humans. Arch. Toxicol. 55, 151-154). Long-term pretreatment of rats with CCl4 slightly reduces the amount of MMA and DMA excreted in urine following a challenge dose of inorganic arsenic. This effect may result from a reduction of GSH transferase activity by CCl4. This study demonstrates the important role of liver GSH in the metabolism of inorganic arsenic in vivo.

A comparative study, with 40 chemicals, of the efficiency of the Salmonella assay and the SOS chromotest (kit procedure)

A comparison was made, for 40 compounds belonging to different chemical classes, of the mutagenicity as measured by the Salmonella assay and of the SOS-inducing potency as measured by the SOS chromotest kit procedure. It was found that most (78%) of the chemicals described as mutagens/carcinogens (14 compounds) were detected with a simplified Ames test procedure, using 3 strains (TA 97, TA 98, TA 100) and 3 concentrations of the tested material. The SOS chromotest, carried out following the recommendations of the commercially available kits, revealed that only 4 Ames test-positive compounds were mutagenic towards E. coli strain PQ 37.

Development of a method to monitor low molecular mass hydrocarbons in exhaled breath of man: preliminary evaluation of its interest for detecting a lipoperoxidation process in vivo

Low molecular mass hydrocarbons, particularly ethane and pentane, have been measured in expired air of man. The air is collected into 5-10 l polyamide bags. After removal of water vapour and CO2, the hydrocarbons are concentrated on a silicagel column kept at 0 degree C. The column desorption is carried out at 290 degrees C, and the gases are analysed by gas chromatography. A slight but statistically significant increased pentane production was detected in cirrhotic patients.

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.

Epidemiological survey among workers exposed to manganese: effects on lung, central nervous system, and some biological indices

A cross-sectional epidemiological study was carried out among 141 male subjects exposed to inorganic manganese (Mn) in a Mn oxide and salt producing plant (mean age 34.3 years; duration of exposure, mean 7.1 years, range 1-19 years). The results were compared with those of a matched control group of 104 subjects. The intensity of Mn exposure was moderate as reflected by the airborne Mn levels and the concentrations of Mn in blood (Mn-B) and in urine (Mn-U). A significantly higher prevalence of cough in cold season, dyspnea during exercise, and recent episodes of acute bronchitis was found in the Mn group. Lung ventilatory parameters (forced vital capacity, FVC; forced expiratory volume in one second, FEV1; peak expiratory flow rate, PEFR) were only mildly altered in the Mn group (smokers) and the intensity and the prevalence of these changes were not related to Mn-B, Mn-U, or duration of exposure. There was no synergistic effect between Mn exposure and smoking on the spirometric parameters. Except for a few nonspecific symptoms (fatigue, tinnitus, trembling of fingers, increased irritability), the prevalence of the other subjective complaints did not differ significantly between the control and Mn groups. Psychomotor tests were more sensitive than the standardized neurological examination for the early detection of adverse effects of Mn on the central nervous system (CNS). Significant alterations were found in simple reaction time (visual), audioverbal short-term memory capacity, and hand tremor (eye-hand coordination, hand steadiness). A slight increase in the number of circulating neutrophils and in the values of several serum parameters (ie, calcium, ceruloplasmin, copper, and ferritin) was also found in the Mn group. There were no clear-cut dose-response relationships between Mn-U or duration of Mn exposure and the prevalence of abnormal CNS or biological findings. The prevalences of disturbances in hand tremor and that of increased levels of serum calcium were related to Mn-B. The response to the eye-hand coordination test suggests the existence of a Mn-B threshold at about 1 microgram Mn/100 ml of whole blood. This study demonstrates that a time-weighted average exposure to airborne Mn dust (total dust) of about 1 mg/m3 for less than 20 years may present preclinical signs of intoxication.

Relationship between external and internal parameters of exposure to manganese in workers from a manganese oxide and salt producing plant

In a plant producing manganese (Mn) oxides and salts, 11 different workplaces were identified. The current exposure to airborne Mn (total dust, personal sampling, n = 80) varied from 0.07 to 8.61 mg/m3. The geometric mean and median values amounted approximately to 1 mg/m3 and the 95th percentile was 3.30 mg/m3. The concentration of Mn in blood (Mn-B) in a group of 141 Mn-exposed male workers ranged from 0.10-3.59 micrograms/100 ml compared to 0.04-1.31 micrograms/100 ml in a group of 104 control subjects. The ranges of the concentrations of Mn in urine (Mn-U) were 0.06-140.6 and 0.01-5.04 micrograms/g creatinine for the exposed and control groups, respectively. The average level of Mn-B in the Mn group was more than twice as high as in the control group (arithmetic mean, 1.36 vs 0.57 microgram/100 ml) and that of Mn-U was ten times higher in the Mn group (geometric mean, 1.56 vs 0.15 microgram/g creatinine). The Mn-B level did not change significantly after 8 h of Mn exposure, whereas the Mn-U level dropped rapidly when exposure ceased (half-life less than 30 h). On an individual basis, neither Mn-B nor Mn-U correlated with the current levels of Mn-air or duration of Mn exposure. There was also no relationship between Mn-B and Mn-U. On a group basis, there was no correlation between the mean Mn-B levels and the current levels of Mn-air at each workplace.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of aluminum on porphyrin metabolism in hemodialyzed patients

In patients with renal failure and on chronic hemodialysis, serum aluminum, serum delta-aminolevulinic acid, serum porphobilinogen and erythrocyte zinc protoporphyrin (ZPP) are significantly elevated, whereas erythrocyte delta-aminolevulinic acid dehydratase activity (ALAD, values in percent) is significantly reduced. The last two parameters (ZPP and ALAD) are statistically related to serum aluminum concentration (Al-S), but only the correlation between Al-S and ALAD remains statistically significant after standardization for the degree of renal insufficiency (expressed in terms of urea level). This study does not support the hypothesis that the retention of aluminum is responsible for the increase of ZPP in uremic patients on dialysis. The disturbances of porphyrin metabolism found in patients with renal failure and on chronic dialysis are not similar to those observed in porphyria cutanea tarda.

Epidemiological survey among workers exposed to manganese: effects on lung, central nervous system, and some biological indices

A cross-sectional epidemiological study was carried out among 141 male subjects exposed to inorganic manganese (Mn) in a Mn oxide and salt producing plant (mean age 34.3 years; duration of exposure, mean 7.1 years, range 1-19 years). The results were compared with those of a matched control group of 104 subjects. The intensity of Mn exposure was moderate as reflected by the airborne Mn levels and the concentrations of Mn in blood (Mn-B) and in urine (Mn-U). A significantly higher prevalence of cough in cold season, dyspnea during exercise, and recent episodes of acute bronchitis was found in the Mn group. Lung ventilatory parameters (forced vital capacity, FVC; forced expiratory volume in one second, FEV1; peak expiratory flow rate, PEFR) were only mildly altered in the Mn group (smokers) and the intensity and the prevalence of these changes were not related to Mn-B, Mn-U, or duration of exposure. There was no synergistic effect between Mn exposure and smoking on the spirometric parameters. Except for a few nonspecific symptoms (fatigue, tinnitus, trembling of fingers, increased irritability), the prevalence of the other subjective complaints did not differ significantly between the control and Mn groups. Psychomotor tests were more sensitive than the standardized neurological examination for the early detection of adverse effects of Mn on the central nervous system (CNS). Significant alterations were found in simple reaction time (visual), audioverbal short-term memory capacity, and hand tremor (eye-hand coordination, hand steadiness). A slight increase in the number of circulating neutrophils and in the values of several serum parameters (ie, calcium, ceruloplasmin, copper, and ferritin) was also found in the Mn group. There were no clear-cut dose-response relationships between Mn-U or duration of Mn exposure and the prevalence of abnormal CNS or biological findings. The prevalences of disturbances in hand tremor and that of increased levels of serum calcium were related to Mn-B. The response to the eye-hand coordination test suggests the existence of a Mn-B threshold at about 1 microgram Mn/100 ml of whole blood. This study demonstrates that a time-weighted average exposure to airborne Mn dust (total dust) of about 1 mg/m3 for less than 20 years may present preclinical signs of intoxication.

Arsenic uptake, cytotoxicity and detoxification studied in mammalian cells in culture

The cytotoxicity of trivalent and pentavalent inorganic arsenic salts was determined in mouse fibroblasts in vitro. Concentrations of As (III) in the microM range led to a reduction of proliferation and viability with a concomitant increase in LDH release and stimulation of lactic acid production. Similar effects were noted with approximately 10-fold greater molar concentrations of As(V). Cells pretreated with a low As(III) concentration are less sensitive to toxic doses of As(III) or As(V). Uptake of As(III) by the fibroblasts is greater than that of As(V). Both forms of inorganic arsenic are converted intracellularly to monomethylarsonic (MMA) and dimethylarsinic (DMA) acids, which are then released into the culture medium. In As-pretreated cells, which are more resistant to As toxicity, biotransformation of inorganic arsenic to MMA and DMA is increased.

Study of inorganic arsenic methylation by rat liver in vitro: relevance for the interpretation of observations in man

The biotransformation of inorganic arsenic by rat liver in vitro leads to the production of a monomethylated and a dimethylated arsenic derivative, measured by flameless atomic absorption as monomethylarsonic (MMA) and dimethylarsinic (DMA) acids respectively. The methylating activity is localized in the cytosol and accepts only As3+ as substrate. Its optimum pH lies between 7.5 and 8.0, and reduced glutathione (10(-2)M) is required for full activity. S-Adenosylmethionine is the essential methyl group donor and corrinoïd derivatives act synergistically. An excess of substrate and the addition of mercuric ions prevent the formation of the dimethylated arsenic derivative without affecting that of the monomethylated compound. This indicates that two different enzymatic activities are involved in the methylation of inorganic arsenic in mammals. Previous observations in man (Buchet et al. 1981 b, 1984) and the results of the present study suggest that DMA production results from the subsequent methylation of the MMA precursor, although the possibility that metabolites are also produced by two completely independent pathways cannot yet be conclusively rejected. The kinetics of MMA and DMA production provide an explanation for the observations that in volunteers given increasing amounts of As3+, the urinary excretion of DMA levels off faster than that of MMA and in patients acutely intoxicated with As3+, several days may elapse before DMA becomes the preponderant metabolite. The results of the present study also suggest that the reduction of MMA production associated with an increased synthesis of DMA found in patients with liver diseases given a standard dose of As3+ might be due to a reduction of As3+ uptake by the liver cells.