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.
Theophylline, a widely prescribed anti-asthmatic, was evaluated for toxic and teratogenic effects in timed-pregnant CD-1 mice. THEO (0, 0.075, 0.15, or 0.20%) was administered continuously in the drinking water on gestational days 6 through 15. Females were weighed and observed daily for clinical signs of toxicity. At sacrifice a total of 23-33 dams (i.e., confirmed-pregnant females) per treatment group were evaluated. The gravid uterus of each dam was weighed, and the status of each uterine implantation site (i.e., resorption, dead fetus, or live fetus) was recorded. Each live fetus was weighed and examined for external, visceral, and skeletal malfofmations.
During THEO treatment, dams exhibited clinical signs of toxicity consisting primarily of piloerection, weight loss, and rough coat. No dose-related maternal. deaths occurred during this investigation. Maternal body weight on gd 11, 15, and 17, maternal weight gain during treatment (i.e., gd 6 through 15) and gravid uterine weight decreased in a doserelated manner and exhibited a significant difference among treatment groups with the high dose group significantly below controls. Maternal weight gain during gestation (i.e., gd 0 through 17), corrected maternal weight gain (i.e. , maternal weight gain during gestation minus gravid uterine weight) , and absolute maternal liver weight also exhibited a decreasing trend with respect to increasing dose and a significant difference among dose groups, with both the 0.15% and 0.20% dose groups significantly below controls. Relative maternal liver weight (i.e. , percent body weight) was unaffected by treatment. Water consumption by confirmed-pregnant mice (g/kg/day) did not differ among treatment groups prior to initiation of treatment (gd 0-6) or after treatment was completed (gd 15-17). However, during treatment (gd 6-15) and during the entire gestation period (gd 0-17), maternal water consumption decreased in a dose-related manner and was significantly depressed below controls in both the 0.15% and 0.20% dose groups. The mean calculated intake of theophylline during the treatment period was 0, 282.0, 372.1, and 396.4 mg/kg/day for the 0 through 2.0% dose groups, respectively. Food consumption by maternal animals (g/kg/day) did not differ among treatment groups prior to initiation of treatment or during treatment. However, after treatment had been discontinued and during the entire gestation period, maternal food consumption exhibited a significant treatmentrelated trend toward decreasing with increasing dose.
There were no differences among treatment groups in the number of corpora lutea or implantation sites per dam, or in the percent preimplantation loss. THEO treatment had no effect on the percent of dead fetuses per litter (i.e., fetuses weighing greater than 0.3 g, having discernable digits and exhibiting no vital signs at uterine dissection on gd 17), or on the number of litters with one or more dead fetuses, nonlive implants (i.e., resorptions and dead fetuses), or adversely affected (i.e. , resorptions, dead fetuses, and malformed liver fetuses) implants. The percent of resorptions, nonlive implants and adversely affected implants per litter (i.e., resorptions, dead fetuses, and malformed live fetuses) per litter increased in a dose-related manner and exhibited a significant difference among dose groups, with the 0.15% and 0.20% dose groups significantly above controls. The number of litters with one or more resorptions exhibited a significant dose effect, with the 0.15% dose group, only, significantly above controls. THEO treatment did not affect the number of live fetuses per litter or the percent of live male fetuses per litter. Average fetal body weight per litter (male, female, and combined) decreased in a dose-related manner and exhibited a significant main effect for dose with the 0.15% and 0.20% dose groups significantly below controls.
THEO (0, 0.075, 0.15, or 0.20% in drinking water) administered continuously from gd 6 to gd 15 resulted in a significant dose-related trend toward an increase in the percent of live fetuses malformed per litter and the percent of live female fetuses malformed per litter, although no statistically significant differences among dose groups were observed. Malformed fetuses per litter occurred with an incidence of 0.29, 0.71, 3.00, and 2.30% for the vehicle control, low, medium, and high dose groups, respectively. The proportion of live male fetuses malformed per litter were unaffected by treatment. The incidence of litters with one or more malformed live fetuses exhibited a significant trend toward a dose-related increase. The incidence of litters with external malformations also increased in a dose-related manner; manner the incidence of litters with skeletal or visceral malformations was unaffected by THEO treatment.
In conclusion, THEO (0, 0.075, 0.15, or 0.20% in drinking water) administered continuously to timed- pregnant CD-1 mice from gd 6 through gd 15, produced at the middle and high dose levels maternal toxicity, an increase in the percent of resorptions, nonlive implants (i.e., resorptions and dead fetuses), and adversely affected implants (i.e., resorptions, dead fetuses, and malformed live fetuses) per litter, and significantly decreased average fetal body weight per litter. A dose-related increase in the percent of malformed live fetuses per litter was observed for the study as a whole. However, evaluati on of this parameter in each of the three study replicates indicated that a positive response to treatment was obtained only in the third study replicate. Treatment-related responses for all other biological endpoints were consistent across all three study replicates. THEO did not at any dose significantly increase the incidence of visceral or skeletal malformations, but did result in dose- related increase in the incidence of litters with one or more malformed fetuses, and in the incidence of litters with one or more fetuses with external malformations, and a significant increase in resorptions at 0.15% and 0.20%. These doses also produced significant maternal toxicity including decreased maternal body weight, decreased maternal weight gain, decreased food and water consumption, and decreased maternal liver weight.