Metabolism and hepatorenal toxicity due to repeated exposure to styrene in spontaneously hypertensive rats (SHR)

Assessment for Subclinical Kidney Damage in Workers Exposed to Low Concentrations of Hydrocarbons

It has been suggested the risk of hydrocarbon-induced chronic nephropathy is negligible at low exposure levels. The first purpose of the study was to test this hypothesis by selecting a population slightly exposed to hydrocarbons. Moreover, as hypertension might be associated with an increased excretion of nephrotoxic mercapturates, the association between blood pressure and urinary concentration of S-phenylmercapturic acid (S-PMA) was also examined. Lifetime exposure assessment, main tests of subclinical kidney damage, and statistical approach were taken from a previous study that had included primarily moderately or heavily exposed workers and had found hydrocarbon-induced nephrotoxic effects. No nephrotoxic effect of exposure could be ascertained in the present study. S-PMA concentration was not increased in hypertensive workers. Thus, the risk of hydrocarbon-induced chronic nephropathy might be extremely low in workers slightly exposed to hydrocarbons. The negative results of some studies might be due to the low lifetime hydrocarbon exposures of the study populations.

Occupational hydrocarbon exposure and chronic nephropathy

This review aims at discussing the questions raised by the hydrocarbon-related chronic nephropathy and its possible consequence, the hydrocarbon-related chronic renal failure. It has been attempted to adopt the point of view of the clinician. Therefore, the most important part of the review is devoted to a presentation and an analysis of the available data on humans. The main features of the available studies on human subjects are presented, their conclusions discussed in the light of the possible methodological flaws, and practical conclusions drawn. After a discussion of the main difficulties encountered for selecting the suitable exposure indicator, the studies are discussed in order of decreasing quality of the study design (cohort, case-control, cross-sectional studies, and the case reports). It is concluded that a great deal of controversies about chronic hydrocarbon-related nephropathy is explained by differences in the study design and that hydrocarbon-induced nephropathy is probably more than a mere hypothesis, although a causal relationship has not yet been proven. Finally, some practical consequences for dealing with a hydrocarbon-exposed patient diagnosed with a kidney disease and the need for further research are discussed.

Review of the metabolic fate of styrene

Styrene and styrene oxide have been implicated as reproductive toxicants, neurotoxicants, or carcinogens in vivo or in vitro. The use of these chemicals in the manufacture of plastics and polymers and in the boat-building industry has raised concerns related to the risk associated with human exposure. This review describes the literature to date on the metabolic fate of styrene and styrene oxide in laboratory animals and in humans. Many studies have been conducted to assess the metabolic fate of styrene in rats, and investigations on the metabolism of styrene in humans have been of considerable interest. Limited research has been done to assess metabolism in the mouse. The metabolism of styrene to styrene oxide and further conversion to styrene glycol (via epoxide hydrolase), mandelic acid, and phenylglyoxylic acid has been given considerable attention, and is considered to be the major pathway of activation and detoxication for humans. While the hydrolysis of styrene oxide to styrene glycol historically has been the favored pathway for the rat, studies in more recent years have indicated that glutathione conjugation also is a viable and significant pathway for both the rat and the mouse. This pathway has not been established in humans. Mandelic acid and phenylglyoxylic acid have been used as urinary markers of exposure in humans exposed to styrene. Extensive investigations have been conducted on the kinetics of styrene and styrene oxide in rodents. In people, the kinetics of styrene and styrene oxide in the blood of occupationally exposed workers and volunteers have been determined. Pharmacokinetic models developed in the last decade have become increasingly complex, with the most recent physiologically based model describing the kinetics of styrene and styrene oxide. This model shows pronounced species differences in sensitivity coefficients for styrene or styrene oxide between mice, rats, and humans, where mice are the more sensitive species to the Vmax for both epoxide hydrolase and monooxygenase. This result is particularly interesting in light of the recent findings of extensive mortality and hepatotoxicity for mice exposed to relatively low levels of styrene (250 to 500 ppm), while rats and humans exhibit only nasal and eye irritations at exposure concentrations well above 500 ppm.

Serum laminin, hydrocarbon exposure, and glomerular damage

It has been postulated that occupational exposure to hydrocarbons may damage the kidney and lead to glomerulonephritis and chronic renal failure. As laminin is a ubiquitous basement membrane component that seems to play a central part in the structure and function of basement membranes and as the normal renal filtration process is highly dependent on an intact glomerular basement membrane, the serum laminin concentration was examined in a population of workers exposed to hydrocarbons. The hydrocarbon exposure was assessed by exposure surrogates (exposure duration and exposure score). An interaction between occupational exposure to hydrocarbons and hypertension increased the laminin concentration whereas the laminin concentration decreased in workers exposed for a long time probably because of a selection effect. In a subgroup of printers exposed to toluene whose hippuric acid excretion had been recorded for several years this interaction was confirmed when the hippuric acid excretion was substituted for the other exposure indices. In the exposed group, the age-related decline in creatinine clearance was accelerated. These results seem to confirm that occupational exposure to hydrocarbons is a non-specific factor that may promote a deterioration of renal function.

Hydrocarbon exposure, hypertension and kidney function tests

Control and hydrocarbon exposed workers participated in a cross-sectional study about the nephrotoxicity of chronic hydrocarbon exposure. Different markers of glomerular and tubular function as well as the celluria were examined and compared. The results show that the interaction between hypertension and hydrocarbon exposure has an influence on the kidney function. For the clearance the interaction age-exposure seems to play a more important role than age or exposure alone. The most useful markers appear to be the albuminuria, the N-acetyl-beta-D-glucosaminidase activity, the retinol-binding-protein concentration and the creatinine clearance.