Raymond G. York

Terminology of developmental abnormalities in common laboratory mammals (version 1)

This paper presents the first version of an internationally-developed glossary of terms for structural developmental abnormalities in common laboratory animals. The glossary is put forward by the International Federation of Teratology Societies (IFTS) Committee on International Harmonization of Nomenclature in Developmental Toxicology, and represents considerable progress toward harmonization of terminology in this area. The purpose of this effort is to provide a common vocabulary that will reduce confusion and ambiguity in the description of developmental effects, particularly in submissions to regulatory agencies worldwide. The glossary contains a primary term or phrase, a definition of the abnormality, and notes, where appropriate. Selected synonyms or related terms, which reflect a similar or closely related concept, are noted. Nonpreferred terms are indicated where their usage may be incorrect. Modifying terms used repeatedly in the glossary (e.g., absent, branched) are listed and defined separately, instead of repeating their definitions for each observation. Syndrome names are generally excluded from the glossary, but are listed separately in an appendix. The glossary is organized into broad sections for external, visceral, and skeletal observations, then subdivided into regions, structures, or organs in a general overall head to tail sequence. Numbering is sequential, and not in any regional or hierarchical order. Uses and misuses of the glossary are discussed. Comments, questions, suggestions, and additions from practitioners in the field of developmental toxicology are welcomed on the organization of the glossary as well as on the specific terms and definitions. Updates of the glossary are planned based on the comments received.

Rat and rabbit oral developmental toxicology studies with two perfluorinated compounds.

Developmental toxicology (teratology) studies were done on two perfluorinated compounds-perfluorooctanesulfonate (PFOS) and 2-(N-ethylperfluorooctanesulfonamido)ethyl alcohol (N-EtFOSE) in rats and rabbits. Dose selection for these oral developmental toxicity studies were based upon dose-range study results. Dose levels of 0, 1, 5, 10, and 20 mg/kg/day were used for the rat N-EtFOSE study, and dose levels of 0, 0.1, 1.0, 2.5, and 3.75 mg/kg/day were used for both the PFOS and the N-EtFOSE rabbit studies. Although no compound-related deaths occurred in the dosed pregnant females on the developmental toxicity studies, maternal toxicity (reduced body weight gain and feed consumption) was present at higher dose levels in all three studies. At high maternally toxic doses, associated effects occurred in the conceptuses--increased abortions in PFOS and N-EtFOSE rabbits, reduced fetal weights in N-EtFOSE rats and PFOS rabbits, and increased late resorptions in N-EtFOSE rabbits. Detailed external gross, soft tissue, and skeletal fetal examinations failed to reveal any compound-related malformations in either species. Similar results, that is, only effects associated with maternal toxicity, had been found in previously conducted PFOS rat developmental toxicity studies. It was concluded that these perfluorinated compounds were not selective developmental toxicants in either rats or rabbits.

Oral (Drinking Water) Two-Generation Reproductive Toxicity Study of Dibromoacetic Acid (DBA) in Rats

In a two-generation study of dibromoacetic acid (DBA), Crl SD rats (30 rats/sex/group/generation) were provided DBA in drinking water at 0 (reverse osmosis-deionized water), 50,250, and 650 ppm (0,4.4 to 11.6,22.4 to 55.6, and 52.4 to 132.0 mg/kg/day, respectively; human intake approximates 0.1 μg/kg/day [0.0001 mg/kg/day]). Observations included viability, clinical signs, water and feed consumption, body and organ weights, histopathology, and reproductive parameters (mating, fertility, abortions, premature deliveries, durations of gestation, litter sizes, sex ratios and viabilities, maternal behaviors, reproductive organ weights, sperm parameters and implantation sites, sexual maturation). Histopathological evaluations were performed on at least 10 P and F1 rats/sex at 0 and 650 ppm (gross lesions, testes, intact epididymis; 10 F1 dams at 0, 250, and 650 ppm for primordial follicles). Developmental observations included implantations, pup numbers, sexes, viabilities, body weights, morphology, and reproductive performance. At 50 ppm and higher, both sexes and generations had increased absolute and relative liver and kidneys weights, and female rats in both generations had reduced absolute and relative adrenal weights; adrenal changes were probably associated with physiological changes in water balance. The livers and kidneys (10/sex/group/generation) had no histopathological changes. Other minimal effects at 50 ppm were reduced water consumption and a transient reduction in body weight. At 250 and 650 ppm, DBA reduced parental water consumption, body weight gains, body weights, feed consumption, and pup body weights. P and F1 generation male rats at 250 and 650 ppm had altered sperm production (retained step 19 spermatids in stages IX and X tubules sometimes associated with residual bodies) and some epididymal tubule changes (increased amounts of exfoliated spermatogenic cells/residual bodies in epididymal tubules, atrophy, and hypospermia), although inconsistently and at much lower incidences. Unilateral abnormalities of the epididymis (small or absent epididymis) at 650 ppm in four F1 generation male rats were considered reproductive tract malformations. The no-observable-adverse-effect level (NOAEL) and reproductive and developmental NOAELs for DBA were at least 50 ppm (4.5 to 11.6 mg/kg/day), 45,000 to 116,000 times the human adult exposure level. Reproductive and developmental effects did not occur in female rats exposed to DBA concentrations as high as 650 ppm. Based on the high multiples of human exposure required to produce effects in male rats, DBA should not be identified as a human reproductive or developmental risk.

Oral (drinking water) developmental toxicity studies of bromodichloromethane (BDCM) in rats and rabbits.

Crl:CD(SD)IGS BR VAF/Plus (Crl SD) rats and Hra(NZW) SPF rabbits were tested for potential developmental toxicity from bromodichloromethane (BDCM) provided continuously in the drinking water during gestation (gestation days [GDs] 6 to 21 in rats and GDs 6 to 29 in rabbits). Concentrations of 0, 50, 150, 450, or 900 ppm of BDCM were used for rats; 0, 15, 150, 450, or 900 ppm were used for rabbits (in dose range-finding studies, 1350 ppm was excessively maternotoxic to both species). Investigated maternal parameters included viability, clinical signs, water and feed consumption, and body weights. Maternal gross lesions, gravid uterine weights, abnormal placentas, and numbers of corpora lutea, implantation sites, live and dead fetuses, and early and late resorptions were observed at time of Caesarean sectioning (GD 21 in rats; GD 29 in rabbits). Body weights, sex ratios, and morphological abnormalities (external, soft tissue, and skeletal) were noted in the fetuses. Mean consumed doses of BDCM were calculated to be 0, 2.2, 18.4, 45.0, or 82.0 mg/kg/day for the rats, and 0, 1.4, 13.4, 35.6, or 55.3 mg/kg/day for the rabbits (approximate human intake is 0.8 microg/kg/day [0.0008 mg/kg/day] in adults). In pregnant rats, toxicologically important, statistically significant effects included reduced absolute (g/day) and relative (g/kg/day) water consumption values at > or =50 ppm (2.2 mg/kg/day) and reduced body weight gains (also when corrected for gravid uterine weight) and absolute (g/day) and relative (g/kg/day) feed consumption values at >450 ppm (45.0 mg/kg/day). These parameters were also significantly reduced at > or =450 ppm (35.6 mg/kg/day) in pregnant rabbits (significant weight loss occurred in the rabbits at 900 ppm, i.e., 55.3 mg/kg/day). Thus, the maternal no-observable-adverse-effect level (NOAEL) for BDCM was 150 ppm, i.e., 18.4 and 13.4 mg/kg/day in rats and rabbits, respectively. No adverse effects on embryofetal viability, growth, sex ratio, gross external, soft tissue, or skeletal morphology occurred at 900 ppm in rats or rabbits. Minimal delays in the ossification of forepaw phalanges and hindpaw metatarsals and phalanges occurred in rat fetuses at 900 ppm; delays were considered marginal, reversible, and associated with severely reduced maternal weight gain. Therefore, the developmental NOAEL for rats was 450 ppm (45.0 mg/kg/day), whereas in rabbits it was 900 ppm (55.3 mg/kg/day). These NOAELs are 56,250 and 69,120 times the human adult exposure level of 0.0008 mg/kg/day, respectively. Based on the results of these studies, BDCM should not be identified as a risk to development of human conceptuses.

Developmental toxicity of levo-alpha-acetylmethadol (LAAM) in tolerant rats

Mated Crl:CD VAF/Plus female rats, in a range-finding study (n = 5–6 per dose) and a subsequent definitive study (n = 30 per dose) were used to determine the developmental toxicity, including the teratogenic potential of levo-alpha-acetyhnethadol (LAAM) hydrochloride, in tolerant rats. Tolerance was induced by initially administering the drug by gavage (10 ml/kg) at 2 mg/kg/day and increasing the dose every 2 weeks for 12 weeks until the doses of 2, 6, 9, 12, and 15, or 2, 6, and 12 mg/kg/day were achieved in the range-finding or definitive study, respectively. Females were then mated to stock males and treated throughout mating and gestation. Controls received distilled water on a similar regimen. The range-finding experiment was used for initial clinical evaluations and to determine tissue concentrations of LAAM and metabolites. In plasma, liver, and brain collected from dams and fetuses pooled by litter on gestation day 20, LAAM and its two N-demethylated metabolites, norLAAM and dinorLAAM, showed dose-dependent increases in concentration and in tissue to plasma ratios. Tissue to dam plasma ratios were highest in dam liver (17–60), intermediate in fetal liver (3–16), and fetal brain (3–14), and lowest in dam brain (0.8–5.6) and fetal plasma (0.3–2.1). In the definitive study, caesarean section examinations were performed following euthanization on gestation day 20 on all surviving females followed by teratologic examination of the fetuses. Drug-related outcomes, including increased activity, secondary hair loss, scabbing, focal swelling, and material around the nose, were exhibited by all groups receiving LAAM. Maternal toxicity was evident as decreased body weights, with maximum reduction at the 6-mg/kg/day dose, and reduction in feed consumption. There was also evidence of developmental toxicity in the form of postimplantaüon losses at all doses of LAAM. There were no deaths attributable to LAAM. No grossly observable visceral or skeletal anomalies related to LAAM were observed in the fetuses. In conclusion, the no-observable-effect level when administered to tolerant rats was less than 2 mg/kg/day with regard to clinical signs, body weight, body weight gain, and feed consumption, and with regard to developmental toxicity as reflected by postimplantaüon losses. Despite maternal and developmental toxicity, there was no evidence of selective fetal toxicity or teratogenic activity attributable to LAAM.

Evaluation of the Teratogenic Effects of Tri-ortho-cresyl Phosphate in the Long-Evans Hooded Rat

The developmental toxicity of tri-ortho-cresyl phosphate (TOCP) was evaluated in Long-Evans rats. Pregnant rats were treated with 87.5, 175, and 350 mg/kg/day TOCP throughout organogenesis from gestation Days 6 through 18 (Day of sperm = Day 0). The highest dose tested (350 mg/kg) was lethal in 28% of the dams; no maternal deaths or toxicity were observed in the 87.5 or 175 mg/kg dose groups. There were no significant differences noted among the experimental and control groups for preimplantation loss or resorption. Fetal weights for both sexes in the TOCP groups were significantly greater than in the control group; however, no difference among the TOCP groups was observed. Malformation rates were too low to warrant statistical analysis. Numerous soft tissue and skeletal variations were observed in both control and TOCP-treated groups; there were no significant differences in the frequency of variations among the dose groups. The results of this study indicate that TOCP is not teratogenic in the Long-Evans rat.

Peri- and Postnatal Developmental Toxicity of Salcaprozate Sodium (SNAC) in Sprague-Dawley Rats

Salcaprozate sodium (SNAC) (sodium 8-((2-hydroxybenzoyl) amino) octanoate, CAS RN 203787-91-1) is classified as an oral absorption promoter and may be a useful means for improving the absorption of certain nutrients and pharmaceutical agents. Presented herein is a subset of data from a larger study evaluating the potential effects of SNAC on the gestation, parturition, lactation, maternal behavior, and offspring development of rats. Pregnant Crl:CD BR VAF/Plus female rats (F0; n = 25) received SNAC at 1000 mg/kg/d orally (gavage) from implantation through lactation and weaning. F1 pups were exposed in utero and potentially through maternal milk; observations continued through sexual maturity. The study concluded with Caesarean sectioning of F1 dams for litter observations and fetal evaluations. No deaths, abortions, premature deliveries, or gross lesions occurred in (F0) dams. Excess salivation, red perivaginal substance, and slight reductions in body weights, body weight gains, and/or feed intake were noted in late gestation/early lactation. SNAC was associated with a prolonged gestation period, leading to a greater number of dams with stillborn pups, higher number of stillborn pups, and reduced live litter size. Offspring body weights/gains, feed consumption, age of sexual maturation, mating, fertility, behavioral parameters, and organ weights at necropsy were unaffected by SNAC. No gross external changes were observed in F1 or F2 pups. In summary, SNAC administered orally at 1000 mg/kg/d to pregnant rats from gestation to weaning resulted in a slight decrease in maternal body weights (−3.8%) and prolonged gestation, along with an increase in stillbirths, but had no effects on growth and development in surviving offspring.