Pharmacokinetics of primary metabolites 5-hydroxythalidomide and 5'-hydroxythalidomide formed after oral administration of thalidomide in the rabbit, a thalidomide-sensitive species.

The teratogenicity of the chemotherapeutic drug thalidomide is species-specific and affects humans, non-human primates, and rabbits. The primary oxidation of thalidomide in previously investigated rodents predominantly resulted in the formation of deactivated 5'-hydroxythalidomide. In the current study, similar in vivo biotransformations to 5-hydroxythalidomide and 5'-hydroxythalidomide were confirmed by the analysis of blood plasma from male rabbits, a thalidomide-sensitive species, after oral administration of thalidomide (2.0 mg/kg). Similar levels of thalidomide in seminal plasma and in blood plasma were detected using liquid chromatography-tandem mass spectrometry at 4 hr and 7 hr after oral doses in male rabbits. Seminal plasma concentrations of 5-hydroxythalidomide and 5'-hydroxythalidomide were also seen in male rabbits in a roughly similar time-dependent manner to those in the blood plasma after oral doses of thalidomide (2.0 mg/kg). Furthermore, the values generated by a simplified physiologically based pharmacokinetic rabbit model were in agreement with the measured in vivo blood plasma data under metabolic ratios of 0.01 for the hepatic intrinsic clearance of thalidomide to both unconjugated 5-hydroxythalidomide and 5'-hydroxythalidomide. These results suggest that metabolic activation of thalidomide may be dependent on rabbit liver enzymes just it was for cytochrome P450 enzymes in humanized-liver mice; in contrast, rodent livers predominantly mediate biotransformation of thalidomide to 5'-hydroxythalidomide. A developmental toxicity test system with experimental animals that involves intravaginal exposures to the chemotherapeutic drug thalidomide via semen should be considered in the future.

Historical control data on developmental toxicity studies in rats.

Historical control data from prenatal developmental toxicity studies in rats have been used to evaluate whether toxicology outcomes were induced by exposure to a chemical or were within the range of spontaneous variation. These data are also important for monitoring animal characteristics. As a follow-up to historical control data from 1998 to 2010, this study analyzed control data from prenatal developmental studies performed in rats from 2011 to 2015. Data were collected from studies performed by 24 Japanese laboratories, including 15 pharmaceutical and chemical companies and nine contract research organizations, in Sprague-Dawley and two-sub-strains of Wistar Hannover rats. The data included maternal reproductive findings at terminal cesarean section and fetal findings, including incidences of spontaneous external, visceral, and skeletal anomalies. No noticeable differences in maternal reproductive data were observed among laboratories. The inter-laboratory variations in the incidences of fetal anomalies seemed to be due to differences in the selection of observation parameters, observation criteria, and classification of the findings, as well as to differences in terminology of fetal alterations. These historical control data may be helpful for adequate interpretation of experimental results and for evaluating the reproductive and developmental toxicities of various chemicals.

Initial hazard assessment of benzyl salicylate: In vitro genotoxicity test and combined repeated-dose and reproductive/developmental toxicity screening test in rats.

Benzyl salicylate is used as a fragrance ingredient and an ultraviolet light absorber, but its toxicity is unknown. Therefore, toxicity tests and hazard classification were conducted for screening assessment under the Japanese Chemical Substances Control Law. Benzyl salicylate was found to be non-genotoxic in vitro based on the chromosomal aberration test using Chinese hamster lung cells. However, the combined repeated-dose and reproductive/developmental screening toxicity test, in which male and female rats were administered benzyl salicylate by gavage at 0, 30, 100, or 300 mg/kg/day for 42 and 41-46 days, respectively, from 14 days before mating until postnatal Day 4, showed that repeated doses had major effects on the thymus, liver, epididymis, and femur at 100 and/or 300 mg/kg/day. Furthermore, although benzyl salicylate had no effect on the estrus cycle, fertility, corpus lutea, or implantation rate, embryonic resorption, offspring mortality, and neural tube defects were observed at 300 mg/kg/day, and the offspring had lower body weights at 30 and 100 mg/kg/day, suggesting teratogenicity similar to other salicylates. Based on the developmental toxicity, this chemical was classified as hazard class 2, with a lowest observed adverse effect level (LOAEL) of 30 mg/kg/day and a D-value of 0.003 mg/kg/day.

Study for collecting background data on Wistar Hannover [Crl:WI(Han)] rats in embryo-fetal development studies--comparative data to Sprague Dawley rats.

The purpose of the present study was to collect the background data on Wistar Hannover [Crl:WI(Han)] (hereafter Wistar Han) rats in embryo-fetal development studies from the 6 safety research facilities of pharmaceutical companies and contract research organizations. In each facility, 20 or 22 female rats were dosed with vehicle solution during the organogenesis period. As a result, no abnormalities in clinical signs and necropsy findings in dams were found. Body weights and food consumption in dams were lower than those in Sprague Dawley (SD) rats. The number of corpora lutea (13.3 vs. 16.0 in SD) and implantations (11.8 vs. 14.7) were fewer, and fetal body weights (3.66 vs. 3.70) and placental weights (0.42 vs. 0.45) tended to be lower than those in SD rats. Regarding the fetal abnormalities, the incidence of several findings such as the persistent left umbilical artery (10.4% vs. 1.1%) and cervical (5.2% vs. 0.4%), full (7.4% vs. 0.9%) or short supernumerary (64.5% vs. 9.9%) and wavy ribs (6.6% vs. 0.3%) was higher than that in SD rats. Our present study showed that they maintained a sufficient number of live fetuses and the difference in the fetal sex ratio was not observed. In conclusion, Wistar Han rats were considered to be a suitable strain for embryo-fetal development toxicity study. Since the incidence of several abnormalities was higher than that in SD rats, it may be said that to accumulate background control data is important to evaluate the embryo-fetal development toxicity study using Wistar Han rats.

An antioxidant, N,N'-diphenyl-p-phenylenediamine (DPPD), affects labor and delivery in rats: a 28-day repeated dose test and reproduction/developmental toxicity test.

A 28-day repeated dose toxicity test and reproduction/developmental toxicity test for N,N'-diphenyl-p-phenylenediamine (DPPD) were conducted in [Crl:CD(SD)] SPF rats. Male and female rats were dosed with DPPD by gavage for 28 days at 0, 100, 300, or 1000 mg/kg bw/day or for a total of 42-46 days at 0, 8, 50, or 300 mg/kg bw/day. No significant adverse effects were observed in the repeated dose toxicity study up to 1000 mg/kg bw/day in both sexes. In the reproduction/developmental toxicity study, two females showed piloerection, hypothermia, and pale skin; one died and the other showed dystocia on day 23 of pregnancy at 300 mg/kg bw/day. Another female delivered only three live pups at 300 mg/kg bw/day. A significantly prolonged gestation period was observed at 50 and 300 mg/kg bw/day. The NOAELs of repeated dose toxicity and reproduction/developmental toxicity were considered to be 1000 and 8 mg/kg bw/day, respectively.

Nasal instillation of nanoparticle-rich diesel exhaust particles slightly affects emotional behavior and learning capability in rats.

In the present study, in order to reveal novel adverse effects of ultrafine particles (UFP) on the central nervous system, the effects of nanoparticle-rich diesel exhaust particles (NRDEP; count mode diameter, 21.45 nm) on emotional behavior, learning capability and brain neurotransmitter levels were studied in rats by intranasal instillation (iNI). NRDEP (10 and 50 µg/rat) was instilled into 2-week old infant, male rats once a week for 4 weeks. Spontaneous motor activity measured was observed to be inverse to the dose level. In active avoidance tests using a shuttle box, NRDEP-treated animals showed a lower avoidance performance than control animals given air-instillation. The levels of dopamine and its metabolite (DOPAC) in the medial mammillary nucleus of the brain tended to be lower in the NRDEP-treated animals. From these results, although the effects of NRDEP by iNI on the emotionality and the brain neurotransmitter levels were not fully clear, the results obtained by avoidance testing suggested involvement of UFP in learning capability.

[Neurobehavioral toxicity of acrylamide and IDPN (3,3'-iminodipropionitrile) in rats by 28-day oral administration--problems encountered in collaborative study and a commentary on conducting neurobehavioral testing].

In order to clarify technical problems in evaluating neurotoxicity of chemicals and to solve them, a collaborative study with a common protocol was conducted at 11 domestic safety research laboratories. In the collaborative study, acrylamide and IDPN (3,3'-iminodipropionitrile), which are known neurotoxicants, were used, and the chemicals were orally administered to rats for 28 days. In addition to the clinical observation done routinely, detailed clinical observation, sensory and motor function tests including grip strength and motor activity were performed to evaluate neurobehavioral toxicity with reference to Functional Observational Battery (FOB). In general, neurobehavioral toxicity of the two chemicals was detected in the collaborative study. However, we also encountered technical problems, since neurobehavioral testing was unfamiliar to us. In the present report, we describe the major problems and how to solve them, and briefly explain the neurobehavioral testing procedure.