Recent progress in safety evaluation studies on plasticizers and plastics and their controlled use in Japan.
Recent experimental studies in Japan on the evaluation of potential health hazards from phthalate esters used in manufacturing poly (vinyl chloride) as well as several plastics for medical devices and for food containers and packages were introduced. Development of pulmonary granuloma formation after intravenous injection of diethylhexyl phthalate was assumed to be dependent on the particle size of the phthalate in vehicle used. Dietary administration of large amount of diethylhexyl phthalate and dibutyl phthalate produced renal cysts in mothers and in descendants in reproduction studies in mice. Cytotoxicity and mutagenicity of the phthalates and several plastics and resins were also examined by in vivo and in vitro studies. Hematological parameters examined in rabbits after repeated intravenous injection of diethylhexyl phthalate and after implantation of plastics in aorta for 3--6 months did not show any significant change. A slow decrease of radioactivity was observed in adipose tissue of rats following oral administration of 14C-labeled diethylhexyl phthalate. tthe administrative action on phthalates by the Japanese Ministry of Health and Welfare is briefly reviewed. (+info)
The effect of peroxisome proliferators on mitochondrial bioenergetics.
Peroxisome proliferators are a group of structurally diverse chemicals that cause the proliferation of peroxisomes in rodents. The purpose of this investigation was to test the hypothesis that the shared effect of these compounds on peroxisome proliferation is mediated through a common inhibitory effect on mitochondrial bioenergetics. Freshly isolated rat liver mitochondria were energized with succinate. The effect of the chemicals on mitochondrial bioenergetics was analyzed by monitoring calcium-induced changes in membrane potential and swelling, as well as changes in mitochondrial respiration. Mitochondrial membrane potential was measured with a TPP(+)-sensitive electrode, and swelling was recorded spectrophotometrically. Mitochondrial oxygen uptake was monitored with a Clark-type oxygen electrode. Gemfibrozil and WY-14,643 induced the mitochondrial permeability transition as characterized by calcium-induced swelling and depolarization of membrane potential, both of which were inhibited by cyclosporine A. Fenofibrate, clofibrate, ciprofibrate and diethylhexyl phthalate, on the other hand, caused a direct dose-dependent depolarization of mitochondrial membrane potential. However, the mechanism of membrane depolarization varied among the test chemicals. Bezafibrate and trichloroethylene elicited no effect on succinate-supported mitochondrial bioenergetics. The results of this investigation demonstrate that although most, but not all, peroxisome proliferators interfere with mitochondrial bioenergetics, the specific biomolecular mechanism differs among the individual compounds. (+info)
Hepatic hyperplasia and cancer in rats: alterations in copper metabolism.
We previously demonstrated that rats exposed to the peroxisome proliferator (PP) diethylhexylphthalate (DEHP) had reduced serum ceruloplasmin (CP) oxidase activity, which suggests tissue copper deposition. Copper is highly toxic in excess, and results in cellular damage and hepatocellular carcinomas (HCC). This study addresses changes in expression of copper-related genes and metal accumulation in hyperplastic liver and tumors induced by PP. Male rats were fed diets containing DEHP or clofibrate (CLF) for 3-60 days (hyperplasia) and 4-chloro-6-(2,3 xylidino)-2-pyrimidinyl-thio(N-beta-hydroxyethyl) acetamide for 10 months (HCC). During hyperplasia, an immediate and progressive decrease in serum CP activity was observed (P < 0.05), as were reductions in mRNA levels for both CP and Wilson's disease gene (WD gene, a P-type ATPase) (P < 0.05). Tumor-bearing rats had lower serum CP activity (P < 0.05), and CP and WD gene mRNA levels were reduced in tumors (P < 0.05), and in liver surrounding tumors (SL) (P < 0.05). Metallothionein mRNA showed no consistent changes during hyperplasia. Tumors showed a 2.5-fold induction of metallothionein mRNA (P < 0.05), and a 1.2-fold increase in SL. Temporal increases in liver copper content occurred during hyperplasia, with increases of 2-fold (DEHP) and 3.3-fold (CLF) at 60 days (P < 0.05). Copper content was 2.2-fold higher in tumors (P < 0.05) and 1.7-fold higher in SL; iron did not increase and zinc decreased temporally. Thus, copper accumulation and changes in copper-related gene expression may be contributing factors in liver neoplasia in PP-treated rats. Loss of CP results in decreased free radical scavenger capacity and thus may enhance oxidative damage induced by PPs. (+info)
Chronic peroxisome proliferation and hepatomegaly associated with the hepatocellular tumorigenesis of di(2-ethylhexyl)phthalate and the effects of recovery.
This study compared the levels of cell proliferation and peroxisome proliferation in rodent liver with tumor incidence, to provide more information on the relationship between these events following chronic exposure. Fischer 344 rats were treated with 0, 100, 500, 2500, or 12,500 ppm DEHP, and B6C3F1 mice were treated with 0, 100, 500, 1500, or 6000 ppm DEHP in the diet for up to 104 weeks. Additional groups of rats and mice received the highest concentration for 78 weeks and then the control diet for an additional 26 weeks (recovery groups). Animals were terminated at weeks 79 and 105 for histopathologic examination. Elevated palmitoyl CoA oxidation activity and higher liver-to-body weight ratios were observed for the 2500- and 12,500-ppm groups of rats, and for the 500-, 1500-, and 6000-ppm groups of mice at Week 105. No increase in palmitoyl CoA oxidation activity was evident in the recovery group, and relative liver weights were near control levels following recovery. No hepatic cell proliferation was detected at Weeks 79 or 105 in either species although preliminary data indicated that cell proliferation did occur within the first 13 weeks of exposure. A significantly higher incidence of hepatocellular tumors was only observed for the 2500- and 12,500-ppm group and its recovery group of rats, and for the 500-, 1500-, and 6000-ppm groups and the recovery group of mice. The tumor incidences were reduced for the recovery groups compared with the groups fed DEHP continuously for 104 weeks. The data indicate that high levels of peroxisome proliferation and hepatomegaly are associated with DEHP hepatocarcinogenesis in rodent liver, and that the tumorigenic process may be arrested by cessation of DEHP treatment, suggesting that extended treatment with DEHP acts to promote tumor growth. (+info)
Quantitative analysis of the lobular distribution of S-phase in rat liver following dietary administration of di(2-ethylhexyl)phthalate.
A simple image-analysis method is described, whereby the distribution of hepatocytes that have entered S-phase, as distinguished by the incorporation of bromodeoxyuridine, can be related to the position of the central and portal veins of the hepatic lobule. Hepatocyte S-phase was induced in the livers of male and female F344 rats by administration of di(2-ethylhexyl)phthalate (DEHP) in the diet for 7 days at 2 dose levels, and these livers were used to develop the procedure. The distributions of the S-phase between control and DEHP-treated livers were compared using statistical techniques. The results showed notable differences in the distribution of S-phase between male and female rats as well as limited dose-related effects. (+info)
Influence of plasticizer-free CAPD bags and tubings on serum, urine, and dialysate levels of phthalic acid esters in CAPD patients.
OBJECTIVES: To evaluate the impact of a plasticizer-free device on exposure to di-(2-ethylhexyl) phthalate (DEHP) and its major metabolites in patients on continuous ambulatory peritoneal dialysis (CAPD). DEHP is the most commonly used plasticizer in polyvinyl chloride (PVC) products; it is added to CAPD bags in order to improve the flexibility of the material. Since DEHP leaches out of the plastic matrix, patients on CAPD are exposed to considerable amounts of DEHP and its metabolites. DESIGN: A prospective cross-over study. SETTING: Department of nephrology in a teaching hospital. PARTICIPANTS: Six patients (4 female, 2 male) stable on peritoneal dialysis (PD) for at least 6 months. INTERVENTIONS: Patients were switched from a plasticizer-containing PVC CAPD system (A.N.D.Y. Plus, Fresenius Medical Care, Bad Homburg, Germany) to a polyolefine-made plasticizer-free system (stay-safe, Fresenius). MAIN OUTCOME MEASURES: Prior to and 42 days after the switch, 24-hour effluent dialysate and urine collections were performed and 10 mL blood was drawn. Concentrations of DEHP, mono-(2-ethylhexyl) phthalate (MEHP), phthalic acid (PA), and 2-ethylhexanol (2-EH) in urine, dialysate, and serum were determined using gas chromatography/mass spectrometry. RESULTS: Complete data were obtained from 5 patients. Serum levels of PA decreased significantly during the study period (0.137 +/- 0.078 mg/L vs 0.124 +/- 0.049 mg/L, p = 0.04), and the respective levels of DEHP decreased insignificantly (0.097 +/- 0.076 mg/L vs 0.069 +/- 0.046 mg/L, p = 0.07), whereas the concentrations of MEHP and 2-EH remained unchanged. Urine concentrations of PA were high (0.81 +/- 0.69 mg/L) but did not change substantially (0.70 +/- 0.50 mg/L). Effluent dialysate concentrations of MEHP and PA decreased significantly (0.0176 +/- 0.004 mg/L vs 0.0040 +/- 0.0007 mg/L, p = 0.043 and 0.158 +/- 0.056 mg/L vs 0.111 +/- 0.051 mg/L, p = 0.043, respectively). CONCLUSIONS: Although PD patients seem to be exposed to other sources of phthalates in addition to dialysis, use of plasticizer-free devices may help to reduce potentially immunosuppressive exposure to phthalate esters. (+info)
Chronic toxicity of di(2-ethylhexyl)phthalate in rats.
Fischer 344 rats were treated with 0, 100, 500, 2500, or 12,500 ppm di(2-ethylhexyl)phthalate (DEHP) in the diet for up to 104 weeks. Blood and urine were analyzed at weeks 26, 52, 78, and 104 from 10 animals per sex per group. Survival was slightly but not statistically reduced for rats receiving 12,500 ppm DEHP. Body weights and food consumption were significantly reduced for rats receiving the highest dose level of DEHP and occasionally for the male 2500-ppm group. BUN and albumin were significantly higher and globulin lower at nearly every sampling interval for the 12,500-ppm group compared with the controls. There was an increase in the mean activities of AST and ALT at 104 weeks, but no statistically significant differences were seen. Erythrocyte count, hemoglobin, and hematocrit values for the 12,500-ppm group were significantly lower than controls at nearly every sampling interval. No other differences in hematology were seen. No toxicologically significant changes were observed in urinalysis. At termination, relative lung weights for the 2500- and 12,500-ppm male groups of rats were significantly higher than for the controls. Absolute and relative liver and kidney weights for the 2500- and 12,500-ppm male rats, and liver weights for 12,500-ppm female rats were higher compared with the controls. Absolute and relative testes weights for the 12, 500-ppm male rats were lower compared with the controls. All organs were examined for histopathology. The incidence of hepatocellular lesions has been reported separately and correlated with the induction of peroxisomal enzyme activity (David et al., 1999). A dose level of 500 ppm was the NOEL for peroxisome proliferation. Bilateral aspermatogenesis in the testes, castration cells in the pituitary gland, spongiosis hepatis, and pancreatic acinar cell adenoma were observed for 12,500-ppm male rats. Aspermatogenesis and spongiosis hepatis were observed for 2500-ppm male rats, and aspermatogenesis was seen at 500 ppm. DEHP exposure exacerbated age-, species- or strain-related lesions such as mineralization of the renal papilla and chronic progressive nephropathy in male rats. Kupffer cell pigmentation and renal tubule pigmentation were seen in male and female 12,500-ppm rats. The increased incidence of spongiosis hepatis correlated with increased palmitoyl CoA oxidase activity, but the incidence of pancreatic acinar cell adenoma was increased only at the highest dose level of 12,500 ppm. These lesions, although typical of those seen with other peroxisome proliferators, may respond differently depending on the potency of the peroxisome proliferator. A dose level of 500 ppm (28.9-36.1 mg/kg/day) was considered to be the NOAEL. (+info)
Effects of Di-2-ethylhexyl phthalate (DEHP) on gap-junctional intercellular communication (GJIC), DNA synthesis, and peroxisomal beta oxidation (PBOX) in rat, mouse, and hamster liver.
The present study evaluated the effect of di-2-ethylhexyl phthalate (DEHP) on gap-junctional intercellular communication (GJIC), peroxisomal beta-oxidation (PBOX) activity, and replicative DNA synthesis in several rodent species with differing susceptibilities to peroxisome proliferator-induced hepatic tumorigenesis. A low (non-tumorigenic) and high (tumorigenic) dietary concentration of DEHP was administered to male F344 rats for 1, 2, 4, and 6 weeks. Additionally, a previously non-tumorigenic dose (1000 ppm) and tumorigenic dose of DEHP (12,000 ppm), as determined by chronic bioassay data, were examined following 2 weeks dietary administration. Male B6C3F1 mice were fed the non-tumorigenic concentration, 500 ppm, and the tumorigenic concentration, 6000 ppm, of DEHP for two and four weeks. The hepatic effects of low and high concentrations of DEHP, 1000 and 6000 ppm, were also examined in male Syrian Golden hamsters (refractory to peroxisome proliferator-induced tumorigenicity). In rat and mouse liver, a concentration-dependent increase in the relative liver weight, PBOX activity, and replicative DNA synthesis was observed at the earliest time point examined. Concurrent to these observations was an inhibition of GJIC. In hamster liver, a slight increase in the relative liver weight, PBOX activity, and replicative DNA synthesis was observed. However, these effects were not of the same magnitude or consistency as those observed in rats or mice. Furthermore, DEHP had no effect on GJIC in hamster liver at any of the time points examined (2 and 4 weeks). HPLC analysis of DEHP and its primary metabolites, mono-2-ethylhexyl phthalate (MEHP), and phthalate acid (PA), indicated a time- and concentration-dependent increase in the hepatic concentration of MEHP. At equivalent dietary concentrations and time points, the presence of MEHP, the primary metabolite responsible for the hepatic effects of DEHP, demonstrated a species-specific response. The largest increase in the hepatic concentration of MEHP was observed in mice, which was greater than the concentration observed in rats. The hepatic concentration of MEHP was lowest in hamsters. Hepatic concentrations of DEHP and phthalic acid were minimal and did not correlate with concentration and time. Collectively, these data demonstrate the inhibition of hepatic GJIC and increased replicative DNA synthesis correlated with the observed dose- and species-specific tumorigenicity of DEHP and may be predictive indicators of the nongenotoxic carcinogenic potential of phthalate esters. (+info)