A toxicokinetic model for styrene and its metabolite styrene-7,8-oxide in mouse, rat and human with special emphasis on the lung.

Styrene (ST) occurs ubiquitously in the environment and it is an important industrial chemical. After its uptake by the exposed mammalian organism, ST is oxidized to styrene-7,8-oxide (SO) by cytochrome P450 dependent monooxygenases. This reactive intermediate is further metabolized by epoxide hydrolase (EH) and glutathione S-transferase (GST).

Distribution and unspecific protein binding of the xenoestrogens bisphenol A and daidzein.

Physiological toxicokinetic (PT) models are used to simulate tissue burdens by chemicals in animals and humans. A prerequisite for a PT model is the knowledge of the chemical's distribution among tissues. This depends on the blood flow and also on the free fraction of the substance and its tissue:blood partition coefficients.

Estimation of a possible tumorigenic risk of styrene from daily intake via food and ambient air.

Concerns of a tumorigenic risk of styrene (ST) originate from the findings that styrene (ST) is metabolized to the genotoxic intermediate styrene-7,8-oxide (SO). Therefore, it was hypothesized that results of animal long-term studies with ST and SO together with the SO tissue burden are sufficient for conducting a 'worst case' estimate of the tumorigenic risk of ST. On this basis we predicted the excess human lifetime risk for lung tumors (p(EXL)) and the highest possible risk for other systemic tumors (p(HPS)) resulting from daily intake of ST via food and ambient air.

The relevance of physical activity for the kinetics of inhaled gaseous substances.

Inhalation is the most important route of absorption for many volatile substances. The inhaled chemical is distributed via the bloodstream into the organs and tissues. It is eliminated mainly unchanged by exhalation and also via metabolism.

Toxicokinetics of inhaled propylene in mouse, rat, and human.

A physiological toxicokinetic (PT) model was developed for inhaled propylene gas (PE) in mouse, rat, and human. Metabolism was simulated to occur in the liver (90%) and in the richly perfused tissue group (10%). The partition coefficients tissue:air were determined in vitro using tissues of mice, rats, and humans.

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) and congeners in infants. A toxicokinetic model of human lifetime body burden by TCDD with special emphasis on its uptake by nutrition.

Contents of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and of 16 further congeners--polychlorinated dibenzodioxins and dibenzofuranes (PCDD/PCDF)--were determined in lipids of adipose tissue and of livers of 3 stillborns and of 17 infants (0.43-44 weeks old) who died from sudden infant death syndrome. International toxic equivalents (I-TEq) calculated for the sum of TCDD together with all of the 16 congeners (1.

2,3,7,8-Tetrachlorodibenzo-p-dioxin causes unbalanced growth in 5L rat hepatoma cells.

5L cells, dedifferentiated descendents of the rat hepatoma line H4IIEC3, constitute one of the rare continuous lines which are sensitive to the toxic effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). In the present study we investigated the nature of TCDD toxicity in these cells. The following results were obtained: (1) Exposure to 0.

Toxicity of 2,3,7,8-tetrachlorodibenzo-p-dioxin in vitro: H4IIEC3-derived 5L hepatoma cells as a model system.

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) was investigated for its toxicity in 5L-cells, descendents of the hepatoma line H4IIEC3. TCDD reduced the proliferation of 5L-cells by about 50%, with half-maximum inhibition at 0.1-0.

Arylamine N-acetyltransferase activities in cell lines of mouse, rat, hamster and man differing in their sensitivity to 1,6-dinitropyrene.

This study was aimed at monitoring N-acetyltransferase activities of continuous cell lines, which differ in their sensitivity to the toxic effects of nitroaromatic compounds. Transferase activities were measured toward the acetyl acceptors sulfamethazine and p-aminobenzoic acid in partially purified preparation of cytosols. Cell lines such as hamster V79, BHK, rat hepatoma H4IIEC3G- or fibroblast 208F, which are sensitive to 1,6-dinitropyrene (1,6-DNP), possess high transferase activities ranging from 120-270 nmol/min x mg protein.

Differential effects of 12-O-tetradecanoylphorbol 13-acetate on cytochrome P-450-dependent monooxygenase activities in rat hepatoma cells: induction of P-450I and suppression of P-450II.

We have studied the effects of the tumor promoter 12-O-tetradecanoylphorbol 13-acetate (TPA) on cytochrome P-450-dependent monooxygenase activities in several differentiated and dedifferentiated Reuber rat hepatoma cell lines using aryl hydrocarbon (benzo[a]pyrene) hydroxylase (AHH), ethoxyresorufin O-deethylase (EROD), and aldrin epoxidase (AE) as test systems. The following results were obtained: (1) Exposure of cultures to 400 nM TPA for 18-24 h increased AHH activities in the differentiated lines 2sFou, H41IEC3/G- and Fao as well as in the dedifferentiated line 5L, 1.5-2.

Glutathione conjugation protects some, but not all, cell lines against DNA binding of benzo[alpha]pyrene metabolites.

Three major types of cell lines were distinguished according to their capacity for glutathione (GSH) conjugation of extracellularly generated benzo[alpha]pyrene (BaP) metabolites, and the level of DNA binding of such metabolites. (i) Cells, e.g.

Dexamethasone-mediated potentiation of P450IA1 induction in H4IIEC3/T hepatoma cells is dependent on a time-consuming process and associated with induction of the Ah receptor.

The synergistic effect of dexamethasone (DEX) and polycyclic aromatic hydrocarbons on the induction of cytochrome P450IA1 (P450IA1) was examined in H4IIEC3/T Reuber hepatoma cells. P450IA1 activity was determined by the hydroxylation of benzo[a]pyrene (AHH) and deethylation of 7-ethoxyresorufin (EROD). The amount of Ah receptor, i.

Comparison of three rat liver foci bioassays--incidence of preneoplastic foci initiated by diethylnitrosamine.

Three rat liver foci bioassays have been compared with respect to their sensitivity by the histochemical demonstration of preneoplastic foci, and by the biochemical determination of alterations in enzyme activities of serum indicating hepatotoxicity. We studied the initiation/promotion schedules according to Oesterle and Deml (A), and according to Pereira (B, Broad Spectrum Protocol), and the initiation/selection protocol according to Tatematsu et al. (C), with diethylnitrosamine (DEN), given as a single initiating dose of 10 and 30 mg/kg body wt respectively.