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The use of embryonic stem cells for regulatory developmental toxicity testing in vitro--the current status of test development.

The future chemical policy of the European Union as well as the 7th amendment of the cosmetic directive is calling for the development of alternative tests to animal experimentation for toxicological safety testing. In the field of embryotoxicity one of the most promising in vitro models are based on embryonic stem cells. The embryonic stem cell test has already been validated in comparison to in vivo results in an international blind collaboration study. The presented review is discussing the use, limitations and further needs for the test in order to be fully suitable for regulatory acceptance. In this context, it is summarized which requirements for an in vitro embryotoxicity test have to be fulfilled for regulatory toxicity testing. In addition, an overview about the current status of test development of other embryonic stem cell tests is presented. Several workshops have reviewed the progress of in vitro tests for developmental toxicity testing. A general consensus of these workshops has been that one single test will not be sufficient to cover all manifestations of developmental toxicity. The establishment of a test battery for developmental toxicity is required. This will be even more challenging since the principles of a composing test strategy and its validation have not been defined yet. Finally, the unique possibility of combining the human embryonic stem cell technology and the microarray techniques might lead to a deeper understanding of the toxicological mechanisms of human developmental toxicants.

Abnormalities, Drug-Induced↗

The reproductive and developmental toxicity of High Flash Aromatic Naphtha.

Catalytic reforming is a refining process that converts naphthenes to aromatics by dehydrogenation to make higher octane gasoline blending components. A portion of this wide boiling range hydrocarbon stream can be separated by distillation and used for other purposes. One such application is a mixture of predominantly 9-carbon aromatic molecules (C9 aromatics, primarily isomers of ethyltoluene and trimethylbenzene), which is removed and used as a solvent--High Flash Aromatic Naphtha. A program was initiated to assess the toxicological properties of High Flash Aromatic Naphtha since there may be human exposure through inhalation or external body contact. The current study was conducted to assess the potential for developmental toxicity in the mouse and for reproductive toxicity in the rat. In the developmental toxicity study in CD-1 mice, exposure of dams by inhalation to near lethal levels (1500 ppm) resulted in fetal mortality, reduced weight, delayed ossification, and an increased incidence of cleft palate. At 500 ppm, a level at which maternal weight gain was slightly reduced, fetal weight gain was also reduced, but there was no other evidence of developmental effects. The lowest exposure level (100 ppm) did not cause any maternal or developmental toxicity. There was no consistent evidence of reproductive toxicity in rats, even at exposure levels which resulted in significantly reduced parental weight gain. In addition, when parental exposure was stopped on GD (gestation day) 20, birth weights as well as postnatal survival were generally similar to control values, even in the 1500 ppm exposure group. Postnatal weight gain was also similar to controls early in weaning, but, if maternal exposure was reinitiated, weight gain was reduced in the high exposure group. However, when exposure was continued until delivery, pups in the high exposure group exhibited reduced litter size, birth weight and poor survival. Thus it was likely that the reduction in fetal weight, seen in the developmental toxicity study in mice, was transient and had no postnatal consequences if maternal exposure was terminated at any time prior to delivery.

Administration, Inhalation↗

Developmental toxicity of purified fumonisin B1 in pregnant Syrian hamsters.

The purpose of this study was to characterize the developmental toxicity of fumonisin B1 (FB1), a mycotoxin produced by Fusarium moniliforme, on fetal Syrian hamsters. Fusarium moniliforme has been associated with a variety of diseases in animals and esophageal cancer in humans. Purified FB1 causes leukoencephalomalacia in horses and is hepatocarcinogenic in rats. Fumonisin B1 has been associated with fetal toxicity in rats and mice and has been suggested to be involved in reproductive failure in pregnant sows. Results from a preliminary developmental toxicity study using an aqueous extract of F. moniliforme corn-culture material in hamsters suggested that FB1 was a developmental toxicant. These results were verified using purified FB1. Six groups of ten time-mated female Syrian hamsters were dosed with 0.0-18 mg kg(-1) day(-1) of FB1 by gavage on days 8-12 of gestation and euthanized on day 15. Live fetuses were weighed and examined for gross external and internal abnormalities and skeletal anomalies. Purified fumonisin B1 was shown to cause dose-dependent fetal death and delayed fetal development without causing fetal abnormalities.

Abnormalities, Drug-Induced↗

Evaluation of the developmental toxicity of isoeugenol in Sprague-Dawley (CD) rats.

Isoeugenol, used as a perfumery and flavoring agent, was evaluated for developmental toxicity. Timed-pregnant CD((R)) outbred albino Sprague-Dawley rats received isoeugenol (250, 500, or 1000 mg/kg/day) or vehicle (5 ml/kg corn oil) by gavage on gestational days (gd) 6 through 19. Maternal food and water consumption, body weight, and clinical signs were monitored at regular intervals throughout gestation. At termination (gd 20), confirmed-pregnant females (23-25 per group) were evaluated for gestational outcome. All live fetuses were weighed and examined for external malformations, and approximately 50% were evaluated for visceral or skeletal malformations. There were no treatment-related maternal deaths. Clinical signs associated with isoeugenol exposure included dose-related evidence of sedation and aversion to treatment (rooting behavior) in all isoeugenol groups, as well as an increased incidence of piloerection at >/= 500 mg/kg/day. Maternal body weight, weight gain, and gestational weight gain (corrected for gravid uterine weight) were reduced at all doses in a dose-related manner. Gravid uterine weight was significantly decreased at the mid and high doses, whereas maternal relative liver weight was increased at all three dose levels. During treatment (gd 6 to 20), maternal relative food consumption was significantly decreased at the high dose, and maternal relative water consumption was elevated in the mid- and high-dose groups. Prenatal mortality (resorption or late fetal death) was unaffected. At 1000 mg/kg/day, average fetal body weight/litter was decreased by 7% (male) or 9% (female). Incidences of fetal morphological anomalies were statistically equivalent among groups, except for an increase in the incidence of unossified sternebra(e), a skeletal variation, at the high dose. In summary, the maternal toxicity lowest observed adverse effect level (LOAEL) was 250 mg/kg/day based primarily on reduced body weight and gestational weight gain (corrected for gravid uterine weight), and the maternal toxicity no observed adverse effect level (NOAEL) was not determined in this study. The developmental toxicity LOAEL was 1000 mg/kg/day based on intrauterine growth retardation and mildly delayed skeletal ossification. The developmental toxicity NOAEL was 500 mg/kg/day.

Abnormalities, Drug-Induced↗

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-acetylmethadol (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 postimplantation 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 postimplantation losses. Despite maternal and developmental toxicity, there was no evidence of selective fetal toxicity or teratogenic activity attributable to LAAM.

Abnormalities, Drug-Induced↗

Developmental toxicity of orally administered thiabendazole in Sprague-Dawley rats and New Zealand white rabbits.

The developmental toxicity of thiabendazole (TBZ) was assessed in studies in New Zealand white rabbits and Sprague-Dawley rats. The doses of TBZ for these studies were based on decreases in maternal weight gain in dose range-finding studies in pregnant females of each species. In rabbits, TBZ was administered orally at doses ranging from 24 to 600 mg/kg body weight/day in two separate studies. In rats, TBZ was administered at doses of 10, 40 or 80 mg/kg body weight/day. In all studies, TBZ was administered daily by gavage in aqueous suspension on gestation days 6 to 17. In the initial rabbit study, weight loss occurred in the 600 mg/kg/day group and weight gain decreased in the 120 mg/kg/day group. In addition, there were four complete litter resorptions and four abortions in the 120 and 600 mg/kg/day groups, respectively. To determine whether these changes (known to occur spontaneously in rabbits) were reproducible, the study was repeated. In this study, decreased maternal weight gain and decreased foetal weights were found at 600 mg TBZ/kg/day, but there was no evidence of selective developmental toxicity. Similarly, in rats TBZ produced decreased maternal weight gain (12 to 26%) associated with slight (5 to 7%) decreases in foetal weights at doses of 30 and 80 mg/kg/day. No changes were found at 10 mg TBZ/kg/day and no evidence of selective developmental toxicity or teratogenicity was found at any dose. On the basis of these results, it is concluded that TBZ is not teratogenic or selectivity foetotoxic in rats or rabbits.

Abnormalities, Drug-Induced↗

Aryl hydrocarbon receptor 2 mediates 2,3,7,8-tetrachlorodibenzo-p-dioxin developmental toxicity in zebrafish.

In order to use the zebrafish as a model vertebrate to investigate the developmental toxicity of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), it is essential to know whether one or both forms of the zebrafish aryl hydrocarbon receptor (AHR), zfAHR1 or zfAHR2, mediate toxicity. To determine the role of zfAHR2, an antisense morpholino approach was used to knock down translation of the protein. No effect of the zfahr2 morpholino (zfahr2-MO) was seen on normal development in embryos not treated with TCDD. Injection of embryos at the 1-2 cell stage with zfahr2-MO decreased TCDD-induced transcription of zfCYP1A mRNA until 96 h post fertilization (hpf), and immuno-histochemical detection of zfCYP1A protein in embryos at 72 hpf revealed a dramatic decrease in expression. The zfahr2-MO completely protected embryos from TCDD-induced edema and anemia and provided protection against TCDD-induced reductions in peripheral blood flow initially; however, a slight reduction in blood flow was observed at later times when the morpholino was no longer effective. Due to persistence of TCDD and decreasing effectiveness of the zfahr2-MO over time, the morpholino provided only transient protection against TCDD-induced inhibition of chondrogenesis of the lower jaw, and no protection against an effect of TCDD that was initiated late in development, blockade of swimbladder inflation. The zfahr2-MO did not protect embryos from TCDD-induced mortality but did produce a 48 h delay in its onset. Endpoints of TCDD developmental toxicity manifested in zfahr2 morphants at late stages of development, beyond 144 hpf, were clearly different from TCDD-exposed embryos injected with a control morpholino. Most strikingly, zfahr2 morphants exposed to TCDD never developed edema. Taken together, these results demonstrate that zfAHR2 mediates several endpoints of TCDD developmental toxicity in zebrafish.

Animals↗

Developmental toxicity evaluation of inhaled 2-ethoxyethanol acetate in Fischer 344 rats and New Zealand white rabbits.

Pregnant Fischer 344 rats and New Zealand white rabbits were exposed to 2-ethoxyethanol acetate (EEA; CAS No. 111-15-9) vapor by inhalation on Gestational Days 6 through 15 (rats) or 6 through 18 (rabbits) at concentrations of 0, 50, 100, 200, or 300 ppm, 6 hr/day. The animals were terminated on Gestational Day 21 (rats) or 29 (rabbits) and fetuses were examined for external, visceral, and skeletal malformations and variations. In rabbits, exposure to 100-300 ppm resulted in maternal toxicity: decreased weight gain at 100-300 ppm, clinical signs at 200-300 ppm, alterations in hematology at 100-300 ppm, reduced gravid uterine weight at termination at 200-300 ppm, and elevated absolute liver weight at 300 ppm. Developmental toxicity was observed at 100-300 ppm: an increased incidence of totally resorbed litters at 200-300 ppm, an increase in nonviable fetuses at 300 ppm, and a decrease in viable implants (live fetuses) per litter at 200-300 ppm. The incidence of fetal malformations (external, visceral, and skeletal) was increased at 200-300 ppm. The incidence of total malformations was 100% at 300 ppm and significantly increased at 200 ppm. Reduced fetal ossification was observed at 100-300 ppm. In rats, exposure to 100-300 ppm also resulted in maternal toxicity: reduced weight gain and reduced food consumption at 200-300 ppm and elevated relative liver weight and alterations in hematology at 100-300 ppm. Absolute maternal liver weight was increased at all EEA exposure concentrations; relative liver weight was increased at 100-300 ppm. Developmental toxicity was observed at 100-300 ppm: increased nonviable implantations/litter (300 ppm), reduced fetal body weight/litter (200-300 ppm), and increased incidence of external (300 ppm), visceral, and skeletal (100-300 ppm) variations indicative of toxicity. The incidence of visceral, skeletal, and total malformations was increased at 200-300 ppm. In conclusion, in both species, inhalation exposure to EEA during organogenesis produced maternal toxicity at 100-300 ppm and developmental toxicity at 100-300 ppm, including teratogenicity at 200-300 ppm. At 50 ppm in both species, there was no evidence of maternal or developmental toxicity, including teratogenicity.

Administration, Inhalation↗

Evaluation of developmental toxicity data: a discussion of some pertinent factors and a proposal.

There is currently no well-accepted standard method for evaluation of developmental toxicity data. This paper presents one approach to the evaluation of developmental toxicity data. We initially identify some pertinent factors that influence the interpretation of animal data and summarize the literature pertaining to these factors. Such factors include the quality and quantity of data and the relationship between maternal and developmental toxicity. We proceed with a discussion of quantitative assessment of data and propose schemes for qualitative and quantitative developmental hazard assessments.

Animals↗

Valproic acid developmental toxicity and pharmacokinetics in the rhesus monkey: an interspecies comparison.

This study was undertaken to assess the developmental toxicity and drug distributional and metabolic characteristics of prenatal valproic acid (VPA) exposure in rhesus monkeys. Oral administration of 20-600 mg/kg/day VPA (approximately 1-15 X human therapeutic dose) to 33 animals on variable gestational days (GD) during organogenesis resulted in dose-dependent developmental toxicity manifested as increased embryo/fetal mortality, intrauterine growth retardation, and craniofacial and skeletal defects. Biphasic plasma elimination curves were observed for total and free VPA on the first (GD 21) and last (GD 50) days of treatment in the 100- and 200-mg/kg/day dose groups. VPA exhibited dose-independent elimination kinetics at the plasma concentrations observed in this study. There was no significant change in pharmacokinetic parameters (maternal plasma elimination rate, area under the curve, peak plasma concentration) between the first and last days of treatment at either dose level. Placental transfer studies indicated that embryos were exposed to half the free VPA concentrations present in maternal plasma on GD 37. Comparisons of interspecies sensitivity to VPA-induced developmental toxicity in the mouse, rat, monkey, and man are made.

Abnormalities, Drug-Induced↗

Overview of a workshop on quantitative models for developmental toxicity risk assessment.

A workshop was held to discuss potential advancements to improve the precision of risk estimates for developmental toxicity. This paper presents an overview of the discussions at the workshop, focusing on the risk assessment process and science policy considerations important in the use of quantitative models. Some of the pertinent biological considerations are reviewed, particularly those related to the repair capacity of the developing organism and how this affects the concept of a threshold for developmental toxicity effects, as well as the maternal and litter influences on developmental toxicity outcomes. Finally, the current status of use of quantitative approaches is described, possible short-term approaches are discussed, and future research needs in this area are outlined.

Abnormalities, Drug-Induced↗

Assessment of the developmental toxicity of deferoxamine in mice.

Deferoxamine (DFO), an efficient chelating agent available for the treatment of iron and aluminium overload, was evaluated for developmental toxicity in Swiss mice. Intraperitoneal injections of DFO were given to pregnant animals at 0, 44, 88, 176, and 352 mg/kg per day on gestational days 6 through 15. Maternal clinical status was monitored daily during and after treatment. Fetal parameters, including external, visceral, and skeletal malformations and variations, were assessed. Mice were killed on day 18. No maternal mortality was observed, but dams exhibited reduced body weight gain during treatment at 88, 176, and 352 mg/kg per day. Body weight at termination, corrected body weight, and food consumption were reduced in all groups. In contrast, the only significant treatment-related embryo/fetal effect was a decrease in the number of live fetuses per litter at 352 mg/kg per day. The no-observable-adverse-effect level (NOAEL) for maternal toxicity of DFO was < 44 mg/kg per day, whereas the NOAEL for developmental toxicity was 176 mg/kg per day. In summary, intraperitoneal administration of DFO to mice during organogenesis produced developmental toxicity in the presence of maternal toxicity. Because of the remarkable maternal toxicity of DFO, extreme caution in the use of this drug is recommended during pregnancy.

Animals↗

Developmental toxic effects of ethylbenzene or toluene alone and in combination with butyl acetate in rats after inhalation exposure.

First, the developmental toxic potential of n-butyl acetate (BA) was examined in Sprague-Dawley rats following whole body inhalation exposure, 6 h day(-1), from day 6 to 20 of gestation, at concentrations of 0, 500, 1000, 2000 and 3000 ppm. Maternal toxicity was evidenced by significant decreases in body weight gain at 2000 and 3000 ppm, and by reduced food consumption at 1000 ppm and higher concentrations. The effects on prenatal development were limited to a significant decrease in fetal weight at 3000 ppm. Thus, inhaled BA was not a selective developmental toxicant. In the second part of this study, the developmental toxic effects of simultaneous exposures to ethylbenzene (EB) and BA, or to toluene (TOL) and BA were evaluated. Pregnant rats were administered EB (0, 250 or 1000 ppm) and BA (0, 500 or 1500 ppm), or TOL (0, 500 or 1500 ppm) and BA (0, 500, 1500 ppm), separately and in combinations, using a 2 x 2 factorial design. The maternal weight gain was reduced after exposure to 1000 ppm EB, to 1500 ppm BA, or to 1500 ppm TOL, either alone or in binary combinations. A significant reduction of fetal weight was associated with exposure to 1000 ppm EB alone, to either mixtures of EB with BA, or to 1500 ppm TOL alone or combined with BA at either concentration. No embryolethal or teratogenic effects were observed whatever the exposure. There was no evidence of interaction between EB and BA or between TOL and BA in causing maternal or developmental effects.

Abnormalities, Drug-Induced↗

Developmental toxicity of boric acid in mice and rats.

Boric acid (BORA), an ingredient of many cosmetics, pharmaceuticals, and pesticides, was tested for developmental toxicity in timed-pregnant Swiss mice and Sprague-Dawley rats (n = 26-28/group). BORA (0, 0.1, 0.2, or 0.4% in feed) was provided throughout gestation to attain steady-state exposure as early as possible during prenatal development. Average doses (mg/kg/day) were 248, 452, or 1003 in mice, and 78, 163, or 330 in rats. To limit prenatal mortality, BORA (0.8% or 539 mg/kg/day) was provided to an additional group of rats on Gestational Days (GD) 6 to 15 only. On GD 17 (mice) or 20 (rats), fetuses were weighed and examined for malformations (external, visceral, skeletal). Mouse dams exhibited mild renal lesions (greater than or equal to 0.1%), increased water intake and relative kidney weight (0.4%), and decreased weight gain (0.4%) during treatment. There was a reduction of fetal body weight (greater than or equal to 0.2%) and an increased incidence of resorptions and malformed fetuses per litter (0.4%). Morphological changes included an increased incidence of short rib XIII (a malformation) and a decreased incidence of rudimentary or full rib(s) at lumbar I (an anatomical variation). Maternal rats exhibited increased liver and kidney weights at greater than or equal to 0.2%, altered water and/or food intake at greater than 0.2%, and decreased weight gain at greater than 0.4%. Average fetal body weight/litter was reduced at all doses. Prenatal mortality was increased only at 0.8%. The incidence of fetal malformations was significantly increased at greater than or equal to 0.2%. The most frequently observed malformations were enlarged lateral ventricles of the brain and agenesis or shortening of rib XIII. In rats, the no-observable-adverse-effect level (NOAEL) for maternal toxicity was 78 mg/kg (0.1%), while in mice the low dose of 248 mg/kg (0.1%) approached the maternal NOAEL with mild renal lesions in only 2 of 10 females. Embryo/fetal toxicity occurred in all groups of rats at greater than or equal to 78 mg/kg (greater than or equal to 0.1%) while the NOAEL for developmental toxicity in mice was 248 mg/kg (0.1%). Thus developmental toxicity occurred below maternally toxic levels in rats as well as in the presence of maternal toxicity in mice and rats.

Abnormalities, Drug-Induced↗

Reproductive and developmental toxicity studies of silicone elastomer Q7-2423/Q7-2551 in rats and rabbits.

The purpose of these studies was to assess the potential adverse effects of silicone breast implant envelope elastomer on general reproduction and fetal development in rats and rabbits. One control and one treatment group of 30 male and 30 female Charles River CD rats and 25 inseminated New Zealand white rabbits per group were used in the one-generation reproductive and developmental toxicity studies, respectively. Two 1.2-cm discs of silicone elastomer were subcutaneously implanted in one site in the left flank and one site in the right-flank of the treated group of rats, while four 2.5-cm discs were implanted in two sites in the left flank and two sites in the right flank of the treated group of rabbits. The size of the elastomer implants was chosen to approximate the expected body burden of women with breast implants. The control animals in both studies received subcutaneous implantation of either 1.2- or 2.5-cm discs of polyethylene of the same number in the same locations. The control and test articles were implanted in the male and female rats at 61 and 47 days, respectively, prior to mating (in the rat reproduction study) and approximately 42 days prior to insemination of female rabbits (in the rabbit developmental toxicity study). Subcutaneously implanted discs of silicone breast implant envelope elastomer did not induce maternal or developmental toxicity before or during pregnancy or during lactation, did not cause any adverse effects on the parents or neonates, and did not impair reproductive performance in the rat reproduction study. No maternal toxicity or adverse developmental effects, including teratogenicity, were observed in the treated groups in the rabbit developmental toxicity study.

Abnormalities, Drug-Induced↗

Prediction of the developmental toxicity hazard potential of halogenated drinking water disinfection by-products tested by the in vitro hydra assay.

A series of seven randomly selected potential halogenated water disinfection by-products were evaluated in vitro by the hydra assay to determine their developmental toxicity hazard potential. For six of the chemicals tested by this assay (dibromoacetonitrile; trichloroacetonitrile; 2-chlorophenol; 2,4,6-trichlorophenol; trichloroacetic acid; dichloroacetone) it was predicted that they would be generally equally toxic to both adult and embryonic mammals when studied by means of standard developmental toxicity "teratology" tests. However, the potential water disinfection by-product chloroacetic acid (CA) was determined to be over eight times more toxic to the "embryonic" developmental portion of the assay than it was to the adults. Because of this potential selectivity, CA is a high-priority item for developmental toxicity tests in pregnant mammals to confirm or refute its apparent unique developmental hazard potential and/or to establish a NOAEL by the route of most likely human exposure.

Animals↗

Developmental toxicity evaluation of acrylamide in rats and mice.

Acrylamide (ACRL), a widely used industrial chemical with neurotoxic effects, was evaluated for developmental toxicity. ACRL in distilled water was administered once daily by gavage on gestational days (gd) 6-17 to mice (0, 3, 15, or 45 mg/kg) and on gd 6-20 to rats (0, 2.5, 7.5, or 15 mg/kg). Following termination (gd 17, mice; gd 20, rats) fetuses were examined for external, visceral, and skeletal malformations. Maternal toxicity during treatment was observed at the highest dose as reduced body weight gain in both species and hindlimb splaying in treated mice only. Weight gain corrected for gravid uterine weight was also reduced in rats at 7.5 and 15 mg/kg/day. Embryo/fetal toxicity was not observed in rats, but fetal weight was reduced in mice administered 45 mg/kg/day. No increase in the incidence of malformations was observed in either species; however, the incidence of variations (predominately extra rib) increased with dose. In summary, administration of ACRL during organogenesis produced maternal and developmental toxicity at 45 mg/kg/day in mice and maternal, but not developmental, toxicity at doses greater than or equal to 7.5 mg/kg/day in rats.

Acrylamide↗

Developmental toxicity of pentostatin (2'-deoxycoformycin) in rats and rabbits.

The developmental toxicity of the potent adenosine deaminase (ADA) inhibitor, pentostatin (2'-deoxycoformycin), was investigated in pregnant rats and rabbits administered daily iv doses during organogenesis. Rats received 0, 0.01, 0.10, or 0.75 mg/kg on gestation days 6-15 and rabbits received 0, 0.005, 0.01, or 0.02 mg/kg on gestation days 6-18 and maternal and fetal parameters were evaluated on gestation day 21 (rats) or 30 (rabbits). Live fetuses were examined for external, visceral, and skeletal malformations and variations. In rats, maternal body weight gain and food consumption were significantly suppressed at doses of 0.10 and 0.75 mg/kg during the treatment period but returned to control levels during posttreatment. Increased postimplantation loss and decreased numbers of live fetuses, litter size, and fetal body weight were observed at 0.75 mg/kg. A statistically significant increase in the incidence of vertebral malformations occurred at 0.75 mg/kg. The incidence of certain skeletal variations (extra presacral vertebrae, extra ribs, hypoplastic vertebrae) was also increased at 0.75 mg/kg. Ossification of cervical centra was reduced at 0.75 mg/kg compared with controls. In rabbits, marked maternal toxicity (death, body weight loss, and decreased food consumption) and reproductive toxicity (abortion and premature delivery) occurred in all pentostatin-treated groups. However, there were no significant effects on number of live fetuses, pre- or postimplantation loss, litter size, or fetal body weights in the animals with live litters. There was also no apparent increase in the incidence of malformations or variations in the live fetuses of pentostatin-treated rabbits. Thus, these studies demonstrate developmental toxicity of pentostatin in rats and rabbits, and teratogenicity in rats, at maternally toxic doses.

Abnormalities, Drug-Induced↗