Renal histopathology in toxicity and carcinogenicity studies with tert-butyl alcohol administered in drinking water to F344 rats: a pathology working group review and re-evaluation.

An independent Pathology Working Group (PWG) re-evaluated the kidney changes in National Toxicology Program (NTP) toxicology/carcinogenicity studies of tert-butyl alcohol (TBA) in F344/N rats to determine possible mode(s) of action underlying renal tubule tumors in male rats at 2-years. In the 13-week study, the PWG confirmed that the normal pattern of round hyaline droplets in proximal convoluted tubules was replaced by angular droplet accumulation, and identified precursors of granular casts in the outer medulla, changes typical of alpha(2u)-globulin (α(2u)-g) nephropathy. In the 2-year study, the PWG confirmed the NTP observation of increased renal tubule tumors in treated male groups. Linear papillary mineralization, another hallmark of the α(2u)-g pathway was present only in treated male rats. Chronic progressive nephropathy (CPN) was exacerbated in high-dose males and females, with a relationship between advanced grades of CPN and renal tumor occurrence. Hyperplasia of the papilla lining was a component of CPN in both sexes, but there was no pelvic urothelial hyperplasia. High-dose females showed no TBA-related nephrotoxicity. The PWG concluded that both α(2u)-g nephropathy and exacerbated CPN modes of action were operative in TBA renal tumorigenicity in male rats, neither of which has relevance for human cancer risk.

Development of a bladder instillation of the indoloquinone anticancer agent EO-9 using tert-butyl alcohol as lyophilization vehicle.

The purpose of this research was to develop a stable bladder instillation of EO-9 for the treatment of superficial bladder cancer. First, stability and dissolution studies were performed. Subsequently, the freeze-drying process was optimized by determination of the freeze-drying characteristics of the selected cosolvent/water system and differential scanning calorimetry analysis of the formulation solution. Furthermore, the influence of the freeze-drying process on crystallinity and morphology of the freeze-dried product was determined with x-ray diffraction analysis and scanning electron microscopy, respectively. Subsequently, a reconstitution solution was developed. This study revealed that tert-butyl alcohol (TBA) can be used to both dramatically improve the solubility and stability of EO-9 and to shorten the freeze-drying cycle by increasing the sublimation rate. During freeze drying, 3 TBA crystals were found: TBA hydrate-ice crystals, crystals of TBA hydrate, and a third crystal, probably composed of TBA hydrate crystals containing approximately 90% to 95% TBA. Furthermore, it was shown that crystallization of TBA hydrate was inhibited in the presence of both sodium bicarbonate (NaHCO3) and mannitol. Addition of an annealing step resulted in a minor increase in the crystallinity of the freeze-dried product and formation of the delta-polymorph of mannitol. A stable bladder instillation was obtained after reconstitution of the freeze-dried product (containing 8 mg of EO-9, 20 mg of NaHCO3, and 50 mg of mannitol per vial) to 20 mL with a reconstitution solution composed of propylene glycol/water for injection (WfI)/NaHCO3/sodium edetate 60%/40%/2%/0.02% vol/vol/wt/wt, followed by dilution with WfI to a final volume of 40 mL.

alpha 2u-Globulin nephropathy, renal cell proliferation, and dosimetry of inhaled tert-butyl alcohol in male and female F-344 rats.

tert-Butyl alcohol (TBA) has been shown to cause kidney tumors in male rats following chronic administration in drinking water. The objective of the present study was to determine whether TBA induces alpha 2u-globulin (alpha 2u) nephropathy (alpha 2u-N) and enhanced renal cell proliferation in male, but not female, F-344 rats, and whether the dosimetry of TBA to the kidney is gender specific. Male and female F-344 rats were exposed to 0, 250, 450, or 1750 ppm TBA vapors 6 h/day for 10 consecutive days to assess alpha 2u-nephropathy and renal cell proliferation and for 1 and 8 days to evaluate the dosimetry of TBA following a single and repeated exposure scenario. Protein droplet accumulation was observed in kidneys of male rats exposed to 1750 ppm TBA, with alpha 2u-globulin immunoreactivity present in these protein droplets. A statistically significant increase in alpha 2u concentration in the kidney, as measured by an enzyme-linked immunosorbent assay, was observed in male rats exposed to 1750 ppm TBA with a exposure-related increase in renal cell proliferation. Renal alpha 2u concentration was positively correlated with cell proliferation in male rat kidney. No histological lesions or increased renal cell proliferation was observed in female rats exposed to TBA compared to controls. The TBA kidney:blood ratio was higher at all concentrations and time points in male rats compared with female rats, which suggests that TBA is retained longer in male rat kidney compared with female rat kidney. Together these data suggest that TBA causes alpha 2u-N in male rats, which is responsible for the male rat-specific increase in renal cell proliferation.

Determination of methyl tert-butyl ether and tert-butyl alcohol in human urine by high-temperature purge-and-trap gas chromatography-mass spectrometry.

Methyl tert-butyl ether (MTBE) is the oxygenated gasoline additive most widely used in the U.S. to reduce the CO emission from motor vehicles. We developed a method using a high-temperature purge-and-trap procedure coupled with capillary gas chromatography-mass selective detection to determine MTBE and its metabolite, tert-butyl alcohol (TBA), in human urine. Several spiked-urine tests were conducted at different purging temperatures (25, 55, and 90 degrees C). The results indicated that the purging temperature affects the recovery of TBA from urine more than the recovery of MTBE. The mean recoveries of MTBE and TBA in the urine samples by the high temperature (90 degrees C) purge-and-trap gas chromatography-mass spectrometry method at different spike levels were 96.5+/-4.7% and 98.4+/-5.7%, respectively. The method was used to evaluate the urinary levels in a single subject exposed through inhalation to 1 ppm MTBE for 10 min in a controlled-environment facility. Increases in MTBE and TBA urinary excretion rates were clearly evident following the exposure to MTBE. Approximately 0.9% of the amount of MTBE inhaled was excreted unchanged as urinary MTBE, and 2.4% was excreted as urinary TBA within 10 h after exposure. The method developed is a simple, effective, sensitive, and reproducible procedure for evaluating human exposure to MTBE.

Adduction of DNA with MTBE and TBA in mice studied by accelerator mass spectrometry.

Methyl tert-butyl ether (MTBE) is a currently worldwide used octane enhancer substituting for lead alkyls and gasoline oxygenate. Our previous study using doubly (14)C-labeled MTBE [(CH(3))(3) (14)CO(14)CH(3)] has shown that MTBE binds DNA to form DNA adducts at low dose levels in mice. To elucidate the mechanism of the binding reaction, in this study, the DNA adducts with singly (14)C-labeled MTBE, which was synthesized from (14)C-methanol and tert-butyl alcohol (TBA), or (14)C-labeled TBA in mice have been measured by ultra sensitive accelerator mass spectrometry. The results show that the methyl group of MTBE and tert-butyl alcohol definitely form adducts with DNA in mouse liver, lung, and kidney. The methyl group of MTBE is the predominant binding part in liver, while the methyl group and the tert-butyl group give comparable contributions to the adduct formation in lung and kidney.

Acute toxicity and cancer risk assessment values for tert-butyl acetate.

tert-Butyl acetate (TBAc) is an industrial chemical with potential uses as a degreaser and in architectural coatings. Limited chronic toxicity data exist for TBAc. However, acute inhalation exposure data are available for TBAc. Additionally, TBAc has been demonstrated to be substantially metabolized to tert-butanol (TBA) in rats, and a positive TBA genotoxicity study suggests that TBA may cause oxidative DNA damage. TBA has been shown to induce tumors in both rats and mice, and the Office of Environmental Health Hazard Assessment has calculated an oral cancer potency factor (CSF) for TBA of 3 x 10(-3)(mg/kg-day)(-1). Therefore, TBAc should be considered to pose a potential cancer risk to humans because of the metabolic conversion to TBA. An acute 1-h reference exposure level of 1 mg/m3 can be calculated from the extrapolated no observed adverse effect level of 50 mg/m3. A CSF of 0.002(mg/kg-day)(-1) can be derived for TBAc, assuming 100% metabolism of TBAc to TBA. An inhalation unit risk value for TBAc of 4 x 10(-7)(microg/m(3))(-1) can then be derived from the CSF value for TBAc by assuming a human breathing rate of 20 m3/day, 70% fractional absorption, and an average human body weight of 70 kg.

NTP technical report on toxicity studies of t-butyl alcohol (CAS No. 75-65-0). Administered by inhalation to F344/N rats and B6C3F1 mice.

t-Butyl alcohol is widely used in the manufacture of perfumes and a variety of cosmetics. It is also used as a raw material in the production of isobutylene, which may be used to produce methyl tertiary butyl ether, a common gasoline additive, or to produce butyl elastomers used in the production of automobile tires. The National Cancer Institute nominated t-butyl alcohol to the NTP for study as a result of a review of chemicals found in drinking water. In addition to the high annual production and the potential for occupational exposure, there is also a potential for human exposure to t-butyl alcohol by the inhalation route from its use as an additive in unleaded gasoline. Therefore, toxicity studies of t-butyl alcohol were conducted in male and female F344/N rats and B6C3F1 mice by whole-body inhalation. Animals were evaluated for hematology, clinical chemistry, urinalysis, reproductive toxicity, and histopathology. The genetic toxicity of t-butyl alcohol was assessed by testing the ability of the chemical to induce mutations in various strains of Salmonella typhimurium and L5178Y mouse lymphoma cells or sister chromatid exchanges and chromosomal aberrations in cultured Chinese hamster ovary cells, and by measuring the frequency of micronucleated erythrocytes in rat bone marrow and mouse peripheral blood. In the 18-day inhalation studies, groups of five male and five female rats and mice were exposed to t-butyl alcohol by inhalation at concentrations of 450, 900, 1,750, 3,500, and 7, 000 ppm for 6 hours per day, 5 days per week, for 12 exposure days. All rats and mice exposed to 7,000 ppm were killed moribund following a single 6-hour exposure. One 3,500 ppm male mouse died on day 3. Final mean body weights of 3,500 ppm male and female rats were significantly lower than those of the controls. Final mean body weights and body weight gains of all other exposed groups were similar to those of the controls. In animals exposed to 3.500 ppm, the thymus weights of male and female rats and female mice were less than those of the controls. The liver weights of male and female mice exposed to 3,500 ppm were greater than those of the controls. No grss or microscopic lesion were present in rats or mice. In the 13-week inhalation studies, groups of 10 male and 10 female rats and mice were exposed to t-butyl alcohol at concentrations of 0, 135, 270, 540, 1,080, and 2,100 ppm for 6 hours per day, 5 days per week, for 13 weeks. One 2,100 ppm and five 1,080 ppm male mice died before the end of the studies. The final mean body weight of 2,100 ppm female mice and the mean body weight gains of 1,080 and 2,100 ppm female mice were significantly lower than those of the controls. Clinical findings of toxicity in the 1,080 ppm male mice died during the studies included rough coats and emaciated appearance, hypoactivity, and prostration. Minimal decreases in hematocrit values, hemoglobin concentrations, and erythrocyte counts occurred in the 1,080 and 2,100 ppm male rats at week 13. Hemoglobin concentrations and/or hematocrit values were also minimally decreased in male rats in the lower exposure groups. At week 13, a minimal decrease in urine pH occurred in the 1,080 ppm female and 2,100 ppm male and female rats. Neutrophilia occurred in the 2,100 ppm male mice. Organ weight differences in exposed rats included increased absolute and relative kidney weights of 1,080 ppm males and 2,100 ppm males and females and increased relative liver weights of 1,080 and 2,100 ppm females. There were no treatment-related gross findings in male or female rats or mice; no microscopic lesion occurred in female rats or male or female mice that survived to the end of the study. In male rats, there was an exposure concentration-related increase in the severity of chronic nephropathy. Splenic lymphoid depletion was present in male mice that died during the studies; this lesion was presumed to be secondary to stress. t-butyl alcohol produced no adverse effects on reproductive parameters in male or female rats or mice. The results of all tests of t-butyl alcohol for induction of genetic damage in vitro and in vivo were negative. In vitro, t-butyl alcohol was negative in Salmonella typhimurium and mouse lymphoma cell mutation test, and it did not induce sister chromatid exchanges or chromosomal aberrations in cultured Chinese hamster ovary cells. These in vitro studies were conducted with and without metabolic activation (S9). In vivo, no increase in the frequency of micronucleated erythrocytes was observed in peripheral blood samples from mice administered t-butyl alcohol in drinking water for 13 weeks. Also, induction or micronucleated erythrocytes was noted in bone marrow cells of rats administered t-butyl alcohol by intraperitoneal injection. In summary, inhalation exposure of rats and mice to t-butyl alcohol resulted in deaths following a single 7,000 ppm exposure and clinical findings of alcohol toxicity (hyper- and hypoactivity, ataxia) at concentrations of 900 ppm and greater in rats and 1,750 ppm and greater in mice. In 13-week studies at concentrations up to 2,100 ppm, only one death (that of a 2,100 ppm mouse) was attributed to chemical exposure. The most notable evidence of toxicity at the end of 13 weeks was limited to males and consisted of increased kidney weights, which correlated microscopically to increased severity of chronic nephropathy. Reproductive parameters in male and female rats and mice were unaffected after 13 weeks of exposure, and the results of all tests for genetic toxicity were negative.

Mechanism of superoxide anion production by hepatic sinusoidal endothelial cells and Kupffer cells during short-term ethanol perfusion in the rat.

BACKGROUND/AIMS: The aim of this study was to clarify the candidate cells for and the mechanism of superoxide anion (O2*-) release into the hepatic sinusoids during short-term exposure to ethanol. METHODS: The rat liver was perfused continuously with ethanol (a substrate for alcohol dehydrogenase) or tert-buthanol (not a substrate for alcohol dehydrogenase) for 20 min at a final concentration of 40 mM. In order to detect O2*- production, MCLA (2-methyl-6-[p-methoxyphenyl]-3,7-dihydroimidazo[1,2-a]pyrazin-3-one), a Cypridina luciferin analogue, was simultaneously infused and MCLA-enhanced chemiluminescence was measured. The effects of gadolinium chloride (GdCL3) (a suppressor of Kupffer cells (KCs)), staurosporine (ST) (an inhibitor of serine-threonine kinases, including protein kinase C), diphenyleneiodonium chloride (DPI) (an inhibitor of NADPH oxidase), ibuprofen (IB) (an inhibitor of cyclooxygenase) and 4-methylpyrazole (4MP) (an inhibitor of ethanol metabolism) on the ethanol-induced chemiluminescence were also evaluated. Sites where O2*- could be released were determined by histochemical detection of nitro blue tetrazolium reduction. RESULTS: Both ethanol and tert-buthanol rapidly caused O2*- release. GdCL3 suppressed the ethanol-induced O2*- release by 61%. Staurosporine and DPI, but neither IB nor 4-MP, also significantly inhibited the ethanol-induced O2*- release. In the histochemical examination, ethanol-stimulated liver showed blue formazan precipitate on both sinusoidal endothelial cells (SECs) and Kupffer cells (KCs), whereas the GdCl3-pretreated liver had the precipitate only on SECs. CONCLUSIONS: This study shows that ethanol itself stimulates both SECs and KCs to release O2*- via activation of NADPH oxidase probably involving protein kinase C (PKC).