Alpha 2u-globulin nephropathy: review of the cellular and molecular mechanisms involved and their implications for human risk assessment.

This paper reviews what is known about the induction of alpha 2u-globulin nephropathy and carcinogenesis. This unique male-rat-specific disease is associated with exposure to an ever-increasing number of chemicals. The processes leading to nephropathy and renal cancer are among the best-understood mechanisms for nongenotoxic chemicals and strongly support that it is a male-rat-specific process that is not relevant for human risk assessment.

Repair of O6-methylguanine and O4-methylthymidine in F344 rat liver following treatment with 1,2-dimethylhydrazine and O6-benzylguanine.

Concentrations of O6-methylguanine, O4-methylthymidine, and N-7-methylguanine were measured in the livers of Fischer 344 rats following treatment with 1,2-dimethylhydrazine (20 mg/kg, s.c.) alone or in combination with the O6-alkylguanine transferase inhibitor O6-benzylguanine (100 mg/kg, i.

Characterization of p53 mutations in methylene chloride-induced lung tumors from B6C3F1 mice.

Mutations of the p53 tumor suppressor gene are the most common defined genetic alterations seen in a wide variety of human cancers. In contrast, little is known about the importance of the p53 gene in chemically induced tumors of rodents, which are widely used as models for the evaluation of human health risks. In this study we examined 54 methylene chloride-induced and seven spontaneously arising lung tumors from female B6C3F1 mice for losses of heterozygosity (LOH) at markers near the p53 gene on chromosome 11.

Incorporating biologically based models into assessments of risk from chemical contaminants.

The general approach to assessment of risk from chemical contaminants in drinking water involves three steps: hazard identification, exposure assessment, and dose-response assessment. Traditionally, the risks to humans associated with different levels of a chemical have been derived from the toxic responses observed in animals. It is becoming increasingly clear, however, that further information is needed if risks to humans are to be assessed accurately.

Molecular dosimetry of DNA and hemoglobin adducts in mice and rats exposed to ethylene oxide.

Experiments involving ethylene oxide (ETO) have been used to support the concept of using adducts in hemoglobin as a surrogate for DNA adducts in target tissues. The relationship between repeated exposures to ETO and the formation of N-(2-hydroxyethyl)valine (HEtVal) in hemoglobin and 7-(2-hydroxyethyl)guanine (7-HEG) in DNA was investigated in male rats and mice exposed by inhalation to 0, 3, 10, 33, or 100 ppm ETO for 6 hr/day for 4 weeks, or exposed to 100 ppm (mice) or 300 ppm (rats) for 1, 3, 5, 10, or 20 days (5 days/week). HEtVal was determined by Edman degradation, and 7-HEG was quantitated by HPLC separation and fluorescence detection.

Styrene and styrene oxide: results of studies on carcinogenicity in experimental animals.

Fourteen long-term toxicity studies were reviewed in an effort to evaluate the potential carcinogenic activity of styrene and styrene oxide in animals. Each study was reviewed and evaluated for detail and adequacy of design, adequacy of reported data and interpretation. The results of the review are: 1.

A comparison of European High Test gasoline and PS-6 unleaded gasoline in their abilities to induce alpha 2u-globulin nephropathy and renal cell proliferation.

Male Fischer-344 rats were administered European High Test gasoline (EHT) (50-500 mg/kg), PS-6 unleaded gasoline (UG) (16-500 mg/kg) or 2,2,4-trimethylpentane (TMP) (0.95-30 mg/kg) by gavage for ten consecutive days. To measure cell replication, rats were exposed to [3H]thymidine continuously over the last 7 days of the exposure period.

Molecular dosimetry of ethylene oxide: formation and persistence of N-(2-hydroxyethyl)valine in hemoglobin following repeated exposures of rats and mice.

The formation of N-(2-hydroxyethyl)valine (HEVal) in hemoglobin was investigated in male F344 rats (10/group) and B6C3F1 mice (20/group) exposed to 0, 3, 10, 33, 100, or 300 (rats only) ppm ethylene oxide (ETO) by inhalation for 6 h/day for 4 weeks (5 days/week) or exposed to 100 (mice) or 300 ppm (rats) ETO for 1 or 3 days, or 1, 2, or 4 weeks (5 days/week). The persistence of HEVal was studied in animals killed up to 10 days after cessation of the 4-week time-course studies. HEVal was determined by a modified Edman degradation and quantitation of the resulting pentafluorophenylthiohydantoin derivative, using gas chromatography-mass spectrometry.

Molecular dosimetry of ethylene oxide: formation and persistence of 7-(2-hydroxyethyl)guanine in DNA following repeated exposures of rats and mice.

The formation of 7-(2-hydroxyethyl)guanine (7-HEG) in DNA of target and nontarget tissues was investigated in male B6C3F1 mice (20/group) and F344 rats (10/group) exposed to 0, 3, 10, 33, 100, or 300 (rats only) ppm ethylene oxide (ETO) by inhalation for 6 h/day for 4 weeks (5 days/week) and mice exposed to 100 ppm ETO for 1 or 3 days or 1, 2, or 4 weeks (5 days/week). The persistence of 7-HEG was studied in mice killed up to 7 days after cessation of the 4-week time-course study. In addition, the formation of O6-(2-hydroxyethyl)guanine and 3-(2-hydroxyethyl)adenine was evaluated in rats exposed to 300 ppm ETO.

Modulation of ethylnitrosourea-induced toxicity and mutagenicity in human cells by O6-benzylguanine.

We have examined the contributions of O6-alkylguanine-DNA alkyl-transferase (AGT) and nucleotide excision repair to the protection of human cells from the toxic and mutagenic effects of ethylnitrosourea. Three human lymphoblastoid cell lines were used: one which possesses both of these DNA repair pathways; one derived from a xeroderma pigmentosum complementation group A patient, which expresses AGT but is deficient in nucleotide excision repair; and a third which does not express AGT but is capable of excision repair. The level of active AGT in the cells was further modulated with the use of the AGT inhibitor, O6-benzylguanine.

In vitro mutational specificity of cisplatin in the human hypoxanthine guanine phosphoribosyltransferase gene.

The in vitro mutational spectra of cisplatin [cis-diamminedichloroplatinum(II)] in exon 3 of the human hypoxanthine guanine phosphoribosyltransferase gene in B-lymphoblasts was examined by a combination of polymerase chain reaction and denaturing gradient gel electrophoresis. Several thousand independent mutants were induced at the hypoxanthine guanine phosphoribosyltransferase locus by cisplatin and were selected en masse by addition of 6-thioguanine to the bulk culture. Polymerase chain reaction was used to amplify exon 3 from the complex mutant population, and denaturing gradient gel electrophoresis was used to separate wild-type DNA sequences from mutant sequences.

Etheno adducts formed in DNA of vinyl chloride-exposed rats are highly persistent in liver.

Preweanling rats were exposed to 600 p.p.m.

Efficient repair of O6-ethylguanine, but not O4-ethylthymine or O2-ethylthymine, is dependent upon O6-alkylguanine-DNA alkyltransferase and nucleotide excision repair activities in human cells.

The formation and persistence of O6-ethylguanine, O4-ethylthymine, and O2-ethylthymine were quantitated in the genomic DNA of human lymphoblasts exposed to 1.0 mM N-ethyl-N-nitrosourea using immunoslot-blot. The three cell lines used included one which lacks O6-alkylguanine-DNA alkyltransferase, one deficient in nucleotide excision repair, and a third which is competent in both of these repair pathways.

Toxicity, mutagenicity, and mutational spectra of N-ethyl-N-nitrosourea in human cell lines with different DNA repair phenotypes.

We examined the toxicity, mutagenicity, and mutational spectra of N-ethyl-N-nitrosourea (ENU) in three Epstein-Barr virus-transformed human lymphoblastoid cell lines, each with a different DNA repair phenotype. One cell line lacks O6-alkylguanine-DNA alkyltransferase (AGT) activity; another, derived from a patient with xeroderma pigmentosum, complementation group A, lacks nucleotide exicision repair (NER) capability, and the third is competent in both repair functions. ENU-induced toxicity and mutagenicity at the hypoxanthine-guanine phosphoribosyltransferase locus were increased to a similar degree relative to the repair-competent cells in both AGT-deficient and NER-deficient cells.

Fidelity of Thermococcus litoralis DNA polymerase (Vent) in PCR determined by denaturing gradient gel electrophoresis.

DNA synthesis fidelities of two thermostable DNA polymerases, Thermus aquaticus (Taq) and Thermococcus litoralis (Tli, also known as Vent), and a non-thermostable enzyme, a modified T7 DNA polymerase (Sequenase), were determined by analyzing polymerase chain reaction (PCR) products using denaturing gradient gel electrophoresis (DGGE). The error rates were 4.4, 8.

The presence of alpha 2u-globulin is necessary for d-limonene promotion of male rat kidney tumors.

In a 2-year carcinogenesis bioassay, d-limonene (dL) induced kidney tumors in male F344 rats, but not in female F344 rats or either sex of mice, d-Limonene-1,2-oxide, a metabolite of dL, has been shown to bind reversibly the male rat-specific urinary protein, alpha2u-globulin (alpha 2u-G), lysosomal degradation than alpha 2u-G alone. This reduced degradation of alpha 2u-G-chemical complex leads to an accumulation of this protein in the proximal convoluted tubules of the male rat kidney and to the morphological changes characteristic for alpha 2u-globulin nephropathy. The only male rat strain known to be resistant to this renal disease is the alpha 2u-G deficient NCI-Black-Reiter (NBR) rat.

Preneoplastic lesions in rodent kidney induced spontaneously or by non-genotoxic agents: predictive nature and comparison to lesions induced by genotoxic carcinogens.

The current literature on non-genotoxic renal carcinogens and the associated neoplastic and preneoplastic lesions has been reviewed in order to determine their occurrence and predictive nature with regard to tumor formation. In addition the mechanisms involved in the genesis of renal tumors are discussed. A more generalized classification of preneoplastic and neoplastic renal lesions was introduced, based on studies conducted with genotoxic and non-genotoxic renal carcinogens.

NCI-Black-Reiter (NBR) male rats fail to develop renal disease following exposure to agents that induce alpha-2u-globulin (alpha 2u) nephropathy.

The NCI-Black-Reiter (NBR) rat is the only strain of male rat known not to synthesize the hepatic form of the low molecular weight protein, alpha 2u-globulin. In previous studies, NBR rats were shown not to develop renal disease when exposed to decalin, a compound known to induce alpha 2u-globulin nephropathy in other rat strains. The objective of this study was to show that the presence of alpha 2u-globulin (alpha 2u) is essential for the development of this syndrome in rats exposed to 2,2,4-trimethylpentane (TMP), 1,4-dichlorobenzene (DCB), isophorone (IP), PS-6 unleaded gasoline (UG), and d-limonene (d-L).

Deletion mutagenesis during polymerase chain reaction: dependence on DNA polymerase.

Polymerase chain reaction (PCR) was performed with two polymerases. Thermus aquaticus DNA polymerase (Taq), and modified T7 DNA polymerase (Sequenase). Both polymerases were used to amplify the same portion of the human 18S rRNA gene.

Species comparison of acrylonitrile epoxidation by microsomes from mice, rats and humans: relationship to epoxide concentrations in mouse and rat blood.

Acrylonitrile (ACN) has been shown to cause tumors of the brain, stomach and Zymbal's gland in rats in several bioassays, but it has not been tested in other species. The carcinogenic risk of humans exposed to ACN is unclear. ACN is metabolized in the liver to 2-cyanoethylene oxide (CEO), which is believed to be the proximate or ultimate carcinogenic species.