The following abstract presents results of a study conducted by a contract laboratory for the National Toxicology Program. The findings may not have been peer reviewed and were not evaluated in accordance with the levels of evidence criteria established by NTP in March 2009. For more information, see the Explanation of Levels of Evidence for Developmental Toxicity. The findings and conclusions for this study should not be construed to represent the views of NTP or the U.S. Government.
Diethylhexyl Phthalate (DEHP), a widely used plasticizing agent, was evaluated for teratogenicity following maternal exposure. Timed pregnant Fischer 344 rats were exposed to DEHP in the feed on gestational days 0 through 20 at levels of 2.0% (20,000 ppm), 1.5% (15,000 ppm), 1.0% (10,000 ppm), 0.5% (5000 ppm) or 0.0% (0 ppm). These dose groups are referred to as DEHP-2.0, DEHP-1.5, DEHP-1.0, DEHP-0.5 or DEHP-0.0, respectively. Dams were weighed on gestational days 0, 4, 8, 12, 16 and 20 (immediately following sacrifice), and were observed for clinical signs of toxicity. Food and water were also measured on these days. At sacrifice on gestational day 20, maternal blood was taken for subsequent plasma zinc analysis, and dams were evaluated for body weight, liver weight, gravid uterine weight and status of uterine implantation sites (i.e., resorptions, dead fetuses, live fetuses). Live fetuses were dissected from the uterus, fetal blood was collected for subsequent plasma zinc analysis, and fetuses were evaluated for live litter size, body weights, sex ratios and gross morphological abnormalities. All live fetuses were examined for visceral malformations employing the Staples' fresh tissue dissection method (Staples, 1974). Half of the fetuses were decapitated prior to dissection and the heads were fixed in Bouin's solution for free-hand sectioning and examination (Wilson's Technique). All fetal carcasses were cleared and stained with Alizarin Red S and examined for skeletal malformations.
There was no maternal mortality in any dose group in this study. There was a significant dose-response trend toward reduced maternal body weight on gestational days 4, 8, 12 and 16, but not gestational day 0 (prior to onset of exposure), with the values from DEHP-1.5 and DEHP-2.0 dose groups significantly lower than in controls for all interim weights. In addition, the value for DEHP-1.0 was significantly lower than controls for gestational days 4, 8 and 12. Maternal weight at sacrifice, maternal weight gain during gestation or treatment, and absolute weight gain were all significant for trend with the values from the DEHP-1.0, DEHP-1.5, and DEHP-2.0 dose groups lower than in controls for all these parameters. Gravid uterine weight exhibited a dose-related decrease,with the value from the DEHP-2.0 dose group significantly lower than in controls. Maternal liver weight and relative liver weight exhibited a dose-related increase with values for all DEHP dose groups higher than for controls. Clinical signs of toxicity, which included piloerection, rough coat, and reduced food intake, were seen in all DEHP dose groups in a dose-related manner. There were no dose-related differences observed in the number of corpora lutea or implantation sites per dam, nor in the percent preimplantation loss. The number and percent of resorptions, non-live (dead plus resorbed), and affected (non-live plus malformed) per litter were all increased in a dose-dependent manner with the values for the DEHP-2.0 group significantly higher than for controls for all of these parameters. Number of live fetuses per litter exhibited a dose-related decrease with the value for DEHP-2.0 significantly lower than in controls. The number and percent of fetal deaths per litter were unaffected by treatment. Among live litters, there were no effects of treatment on number of males or females per litter. There were dose-related decreases in body weight for male and female fetuses combined and separately per litter; values for these three parameters were significantly elevated in the DEHP-0.5 dose group relative to controls, and significantly reduced in all higher dose groups (DEHP 1.0, DEHP-1.5 and DEHP-2.0) relative to control values. There was a significant dose-related upward trend in the percent fetuses malformed per litter, but no significant pairwise comparisons. There were no dose-related differences in the number of fetuses malformed per litter, or in the number or percentage of male or female fetuses malformed per litter. Plasma zinc analysis indicated no apparent differences between DEHP-exposure dams and fetuses and controls.
In conclusion, diethylhexyl phthalate in the feed produced an increased trend in the percent fetuses malformed but no significant pairwise comparisons in F-344 rats exposed during the entire gestation period (gestational days 0 through 20), at dose levels which produced significant maternal and fetal toxicity, i.e., 1.0%, 1.5%, and 2%.