Twenty-six-week oral toxicity of diheptyl phthalate with special emphasis on its induction of liver proliferative lesions in male F344 rats.

The 26-week oral toxicity of diheptyl phthalate (DHP), a peroxisome proliferator-activated receptor α (PPARα) agonist, with special emphasis on the potential induction of hepatocellular proliferative lesions was investigated in this study. DHP was administered to male F344 rats via gavage at 0 (control), 1,000 or 2,000 mg/kg/day for 26 weeks. Body weight gain was significantly lower, whereas food and water consumption was significantly higher in DHP-treated rats compared with controls. DHP-treated rats exhibited decreases in blood triglyceride, total cholesterol, phospholipid and glucose levels, which were likely related to biological effects of the PPARα agonist. Absolute and relative organ weights of the livers with pale brown discoloration and dark brown spots significantly increased in DHP-treated rats. Histopathological examinations revealed remarkable diffuse hypertrophy of hepatocytes with ground-glass appearance, intracytoplasmic inclusion bodies and/or vacuolation in the DHP-treated groups. These findings were associated with increases in serum aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase, and γ-glutamyltranspeptidase. The number and area of glutathione S-transferase placental form positive foci, a marker of hepatocellular preneoplastic lesions in rats, significantly increased in DHP-treated groups. Additionally, proliferating cell nuclear antigen positive liver cell counts in DHP-treated groups were significantly higher than those of the controls. Testicular alterations were not detected histopathologically, whereas absolute and relative prostate weights significantly decreased at both doses. These results indicate that DHP induces liver pre-neoplastic foci, and suggest the possibility that DHP is a possible genotoxic carcinogen in the liver of rats.

Xenopus laevis oocytes expressing human P-glycoprotein: probing trans- and cis-inhibitory effects on [3H]vinblastine and [3H]digoxin efflux.

P-glycoprotein (P-gp; MDR1) recognizes and actively transports many structurally diverse compounds (hydrophobic neutral and cationic). We studied MDR1-mediated drug transport using a high-throughput (96-well) oocyte expression system. MDR1-expressing oocytes contained sufficient ATP levels to conduct fundamental efflux studies; the optimal experimental temperature was 25 degrees C. [(3)H]Vinblastine efflux by MDR1-expressing oocytes was detectable and afforded a K(m) of 145.5+/-25.4microM. [(3)H]Vinblastine (5.6+/-0.3microM) and [(3)H]digoxin (1.0+/-0.1microM) were individually injected into MDR1-expressing oocytes and their efflux monitored. Quinidine and verapamil, known MDR1 substrates/inhibitors, showed trans-inhibition on MDR1-mediated [(3)H]vinblastine and [(3)H]digoxin efflux. Conversely, doxorubicin demonstrated cis-inhibition without trans-inhibition on MDR1-mediated [(3)H]vinblastine efflux. The MDR1-expressing oocyte system offers researchers with an alternative in vitro method to screen compounds and may allow one to probe P-gp drug-drug and/or drug-inhibitor interactions.

Spontaneous Basal cell carcinoma of the submandibular gland in a rat.

At necropsy, a white nodule (about 5 × 3 mm in size) was observed in the right submandibular gland of a 10-week-old female GALAS rat. Histopathologically, oval to spindle-shaped and pale basophilic tumor cells proliferated closely, and formed variably sized foci. The nodule partially spread into or invaded the surrounding normal tissue, and necrotic foci were recognized in the tumor. Immunohistochemically, the nuclei of the tumor cells showed a diffusely positive reaction for p63, and the cytoplasm showed a diffusely positive reaction for cytokeratin and negative reaction for αSMA, vimentin, desmin and S-100. Many tumor cells were positive for PCNA. Ultrastructurally, the tumor cells contained many tonofilaments in the cytoplasm and a few desmosomes at the intercellular portion. Based on these findings, the tumor was diagnosed as a basal cell carcinoma originating from the duct in the rat submandibular gland.

Suppression of atopic-like dermatitis by treatment with antibody to lymphocyte function-associated antigen-1 in NC/Nga mouse.

The effect of a blocking-antibody specific for lymphocyte function-associated antigen-1 (LFA-1) was studied in an atopic-like dermatitis model, which was induced by the repeated application of picrylchloride in NC/Nga mice. Prophylactic treatment with anti-LFA-1 monoclonal antibody (mAb), not therapeutic treatment, significantly inhibited the skin severity score and the acanthosis with ulceration and infiltration of mast cells. Furthermore, the serum immunoglobulin E levels and cytokine production (interleukin-4 and interferon-gamma) by splenocytes stimulated with anti-CD3 antibody were also inhibited by treatment with anti-LFA-1 mAb. Our results suggest that LFA-1 plays an important role in the induction phase of the atopic-like dermatitis model.

Key parameters of sperm motion in relation to male fertility in rats given alpha-chlorohydrin or nitrobenzene.

This study was undertaken to detect key parameters of rat sperm motion in relation to male fertility by comparing the differences in sperm motion induced by treatment with alpha-chlorohydrin (ACH), known to produce spermatotoxicity, and nitrobenzene (NTB), known to produce testicular toxicity. Male rats received ACH (5 or 20 mg/kg/day) or NTB (60 mg/kg/day) for either 3 days or 18 days. Epididymal sperm was assessed for motility using a Hamilton-Thorne Sperm Analyzer (HTM-IVOS). Numerical data for statistical analysis and graphical renditions of sperm motion using parameters in radar charts and reconstructed sperm tracks were analyzed to evaluate sperm motion. Males were allowed to copulate with untreated females and cesarean sections were conducted in order to examine the effects of drug administration on male fertility. Linearity of sperm track (linearity (LIN) and/or straightness (STR)) decreased and/or beat cross frequency (BCF) increased only in ACH groups (5 or 20 mg/kg/day), although the percentage of motile sperm, sperm velocities (average path velocity (VAP), curvilinear (VCL), and straight line velocity (VSL)) and amplitude of lateral head displacement (ALH) decreased on Day 18 in both ACH and NTB (60 mg/kg/day) groups. Furthermore, from the individual reconstructed sperm tracks, it was clear that ACH-treated spermatozoa were characterized by abnormal motion ("jerking") with low vigor (low velocities) and little or no forward progression. Finally, only ACH treatment led to a reduction in pregnancy rate or infertility. Therefore, our results suggest that linearity (especially VSL, STR and LIN) in sperm motion is a key parameter for assessing a chemical's potential to induce male infertility.

Role of substance P in an NC/Nga mouse model of atopic dermatitis-like disease.

BACKGROUND: Atopic dermatitis (AD) can be exacerbated or induced in genetically predisposed individuals by psychological stress, which causes the release of substance P (SP). Therefore, SP may play an etiological role in the mechanisms underlying AD. METHODS: Changes in the number of mast cells and SP-containing mast cells in lesional skin, and the serum concentrations of SP and IgE during the development of AD-like disease up to 8 weeks after the start of picryl chloride (PiCl) induction in NC/Nga mice were examined. RESULTS: Clinical signs and symptoms seen in PiCl-treated NC/Nga mice as a model of AD-like disease began with erythema and haemorrhage, followed by oedema, superficial erosion, deep excoriation, scaling and dryness of the skin, as well as retarded growth, and the changes were exacerbated with an increase in the number of PiCl applications. An increase in the number of mast cells and eosinophil infiltration was observed in the lesional skin. The increase in SP-positive mast cells in the dermis in this model was significant from 1 week after the start of induction treatment, compared with intact mice, and SP-positive nerve fibres were observed in the dermis. CONCLUSION: SP is a crucial mediator of both dermatitis and scratching behaviour in this model.