Developmental Toxicity Evaluation of Inhaled Methyl Isobutyl Ketone in Fischer 344 Rats and CD-1 Mice

Developmental Toxicity Evaluation of Inhaled Methyl IsobutylKetone in Fischer 344 Rats and CD-1 Mice. Tyl, R. W., FRANCE,K. A., FISHER, L. C., PRITTS, I. M., TYLER, T. R., PHILLIPS,R. D., and MORAN, E. J. (1987). Fundam. Appl. Toxicol. 8, 310–327.Pregnant Fischer 344 rats and CD-1 mice were exposed to methylisobutyl ketone vapor (CAS No. 108-10-1) by inhalation on GestationalDays 6 through 15 at concentrations of 0, 300, 1000, or 3000ppm (mean analytical values of 0, 305, 1012, and 2997 ppm, respectively).The animals were sacrificed on Gestational Day 21 (rats) or18 (mice), and live fetuses were examined for external, visceral,and skeletal alterations. In rats, exposure to 3000 ppm resultedin maternal toxicity expressed as clinical signs, decreasedbody weight and body weight gain, increased relative kidneyweight, and decreased food consumption, and in fetotoxicityexpressed as reduced fetal body weight per litter and reductionsin skeletal ossification. In mice, exposure to 3000 ppm resultedin maternal toxicity expressed as exposure-related increasesin deaths (12.0%, 3/25 dams), clinical signs, and increasedabsolute and relative liver weight, and in fetotoxicity expressedas increased incidence of dead fetuses, reduced fetal body weightper litter, and reductions in skeletal ossification. No treatment-relatedincreases in embryotoxicity or fetal malformations were seenin either species at any exposure concentration tested. Therewas no evidence of treatment-related maternal, embryo, or fetaltoxicity (including malformations) at 1000 or 300 ppm in eitherSpecies.     

Developmental Toxicity Evaluation of Inhaled Nitrobenzene in CD Rats

Developmental Toxicity Evaluation of Inhaled Nitrobenzene inCD Rats. TYL, R. W., FRANCE, K. A., FISHER, L. C., DODD, D.E., PRITTS, I. M, LYON, J. P., O'NEAL, F. O., and KIMMERLE,G. (1987). Fundam. Appl. Toxicol. 8, 482–492. PregnantCD (Sprague–Dawley) rats were exposed to nitrobenzenevapor (CAS Registry No. 98-95-3) at 0, 1, 10, and 40 ppm (meananalytical values of 0.0, 1.06, 9.8, and 39.4 ppm, respectively)on gestational days (gd) 6 through 15 for 6 hr/day. At sacrificeon gd 21, fetuses were evaluated for external, visceral, andskeletal malformations and variations. Maternal toxicity wasobserved: weight gain was reduced during exposure (gd 6–9and 6–15) to 40 ppm, with full recovery by gd 21, andabsolute and relative spleen weights were increased at 10 and40 ppm. There was no effect of treatment on maternal liver,kidney, or gravid uterine weights, on pre- or postimplantationloss including resorptions or dead fetuses, on sex ratio oflive fetuses, or on fetal body weights (male, female, or total)per litter. There were also no treatment-related effects onthe incidence of fetal malformations or variations. In summary,during organogenesis in CD rats, there was no developmentaltoxicity (including teratogenicity) associated with exposureto nitrobenzene concentrations that produced some maternal toxicity(10 and 40 ppm) or that produced no observable maternal toxicity(1 ppm).     

Evaluation of the Developmental Toxicity of Ethylene Glycol Monohexyl Ether Vapor in Fischer 344 Rats and New Zealand White Rabbits

Evaluation of the Developmental Toxicity of Ethylene GlycolMonohexyl Ethyl Vapor in Fischer 344 Rats and New Zealand WhiteRabbits. TYL, R. W., BALLANTYNE, B., FRANCE, K. A., FISHER,L. C., KLONNE, D. R., AND PRITTS, I. M. (1989). Fundam Appl.Toxicol. 12, 269-280. Timed pregnant Fischer 344 rats and NewZealand White rabbits were exposed to vapor from ethylene glycolmonohexyl ether (EGHE, CAS No. 112-25-4) for 6 hr/day on gestationaldays (gd) 6 through gd 15 (rats) or gd 6 through gd 18 (rabbits)at analytically measured concentrations (as means ± SD)of 20.8 ± 0.90,41.1 ± 1.77, or 79.2 ± 10.8ppm; control animals were exposed to air alone. Monitors formaternal toxicity were body weight, food and water consumption,clinical signs, and hematology. At sacrifice (gd 2 1 rats, gd29 rabbits) maternal weight, liver weight, and gravid uterineweight were measured. Gestational parameters monitored werenumbers of corpora lutea, preimplantation losses, viable implants,early and late resorptions, and dead fetuses. Live fetuses weresexed, weighed, and examined for external, visceral, and skeletalmalformations and variations. Rabbit maternal toxicity occurredat 79.2 ppm as transient weight gain reduction during the exposureperiod. For maternal rats at 79.2 ppm, there were transientdecrease in body weight and body weight gain during exposure,reduced food consumption, increased water consumption, and excesslacrimation. At 41.1 ppm, maternal body weight gain was reducedduring the exposure period only. There were no treatment- relatedeffects with respect to hematology, necropsy, or gestationalparameters and no significant change in the incidence of malformationsor variations (expressed as total, individual. external, visceral.or skeletal). Thus, exposure of rats and rabbits to EGHE vaporduring the period of organogenesis produced maternal toxicityat near-saturation vapor concentrations (79.2 ppm), but no evidencefor developmental toxicity or teratogenicity. The no-effectvapor concentrations for maternal toxicity were 41.1 ppm forrabbits and 20.8 ppm for rats.     

Evaluation of the Developmental Toxicity of {beta}-(3,4-Epoxycyclohexyl) ethytrimethosysilane in Fischer 344 Rats and New Zealand Whit Rabbits

Evaluation of the Developmental Toxicity of ß-(3,4-Epoxycyclohexyl)ethyltrimethoxysilanein Fischer 344 Rats and New Zealand White Rabbits. TYL, R. W.,BALLANTYNE, B., FISHER, L. C, AND FRANCE, K. A. (1988). FundamAppl Toxicol. 10, 439–452. ß-(3,4-epoxycyclohex-yl)ethyltrimethoxysilane(ECEMS, CAS No. 3388-04-3) is mutagenic in vitro and weaklycarcinogenic in mice after dermal application. Timed pregnantFischer 344 rats and New Zealand white rabbits were dosed withECEMS in corn oil by gavage on gestational days (gd) 6 through15 at doses of 0.0,0.25, 1.0, or 2.5 ml ECEMS/kg for rats and0.0,0.05,0.25, or 0.75 ml ECEMS/kg for rabbits. At terminationon gd 21 (rats) or gd 29 (rabbits), live fetuses were examinedfor external, visceral, and skeletal alterations. In rats, maternaltoxicity was observed at 1.0 and 2.5 ml/kg, as evidenced byreduced weight gain and food consumption during treatment, clinicalsigns of toxicity, reduced body weight on gd 21 (corrected forgravid uterine weight), and increased relative liver weight.There were no significant differences among groups on pre- orpostimplantation loss, fetal body weight/litter, or on the incidenceof malformations. Minimal fetal toxicity, dilated lateral cerebralventricles and reduced ossification in the forelimbs, was observedat 2.5 ml/kg. In rabbits, maternal mortality (2/20 does) andslightly (but statistically significantly) elevated maternalrelative kidney weight were observed at 0.75 ml/kg. Clinicalsigns of toxicity were observed at 0.25 and 0.75 ml/kg. Pre-and postimplantation loss, fetal body weight/litter, and theincidence of malformations were all unaffected by treatment.Minimal fetal toxicity, extra (13th) ribs and reduced ossificationin lumbar arch 4, was observed at 0.75 ml/kg ECEMS. Therefore,administration of ECEMS during organogenesis in rats and rabbitsproduced maternal toxicity at 1.0 and 2.5 ml/kg in rats andat 0.25 and 0.75 ml/kg in rabbits. Minimal fetal toxicity wasobserved at 2.5 ml/kg in rats and at 0.75 ml/kg in rabbits.No embryo-toxicity or teratogenicity was observed in eitherspecies at any dosage. The "no observable effect level" (NOEL)for maternal toxicity was 0.25 ml/kg for rats and 0.05 ml/kgfor rabbits; the NOEL for developmental toxicity was 1.0 ml7sol;kgfor rats and 0.25 ml/kg for rabbits.     

Developmental toxicity evaluation of inhaled toluene diisocyanate vapor in CD rats.

Mated female CD (Sprague-Dawley) rats, 25/group, were exposed to toluene diisocyanate (TDI) vapor, for six h/day on gestational days (gd) 6 through 15, at 0.00, 0.02, 0.10, or 0.50 p.p.m.. Maternal clinical signs, body weights, and feed and water consumption were recorded throughout gestation. At termination (gd 21), maternal body, gravid uterine, and liver weights were recorded. Corpora lutea were counted, and implantation sites were identified: resorptions and dead and live fetuses. All live fetuses were examined for external alterations. One-half of the live fetuses/litter were examined for visceral (including craniofacial) alterations. The remaining intact fetuses/litter were stained with alizarin red S and examined for ossified skeletal alterations. Maternal toxicity at 0.50 ppm consisted of reduced body weights, body weight gains, feed consumption, and clinical signs of toxicity. Water consumption was unaffected. Gestational parameters exhibited no significant treatment-related changes, including pre- and postimplantation loss, sex ratio/litter, or fetal body weights/litter. Incidences of individual malformations, malformations by category (external, visceral, and skeletal), total malformations, individual external and visceral variations, variations by category, and total variations were unaffected. Of 111 skeletal variants observed, only 1, incidence of poorly ossified cervical centrum 5, was increased at 0.50 ppm, indicating possible minimal fetotoxicity, although it occurred in the absence of any other indications of developmental toxicity. Therefore, exposure to TDI vapor by inhalation, during major organogenesis in CD rats, resulted in maternal toxicity and minimal fetotoxicity at 0.50 ppm no observed adverse effect level (NOAEL) for maternal and developmental toxicity was 0.10 ppm. No treatment-related embryotoxicity or teratogenicity was observed.     

Developmental Toxicity Evaluation of Dietary Di(2-ethylhexyl) phthalate in Fischer 344 Rats and CD-1 Mice

Developmental Toxicity Evaluation of Dietary Di(2-ethylhexyl)phthalatein Fischer 344 Rats and CD-I Mice. TYL, R. W., PRICE, C. J.,MARR, M. C. AND KJMMEL, C. A. (1988). Fundam. Appl. Toxicol.10, 395–412. Di(2-ethylhexyl)phthalate (DEHP), a widelyused plasticizing agent, was evaluated for developmental toxicityin timed-pregnant Fischer 344 rats (22-25 dams/dose) and CD-Imice (24-30 dams/dose). DEHP was administered in the diet ongestational Days (gd) 0 through 20 at 0.0,0.5, 1.0, 1.5, or2.0% (rats) and on gd 0 through 17 at 0.00, 0.025,0.05, 0.10,or 0.15% (mice). At termination (gd 20, rats; gd 17 mice), allfetuses were examined for external, visceral, and skeletal malformationsand variations. In rats, maternal toxicity and reduced fetalbody weight per litter were observed at 1.0, 1.5, and 2.0%.Increased resorptions and decreased number of live fetuses/litterwere observed at 2.0%. Maternal food consumption was reducedand water consumption was increased in all DEHP groups. Thenumber and percentage of fetuses malformed per litter were unaffectedby treatment. In mice, maternal toxicity, increased resorptionsand late fetal deaths, decreased number of live fetuses, andreduced fetal body weight per litter were observed at 0.10 and0.15%. Maternal food and water consumption exhibited a dose-relatedupward trend with food consumption significantly increased at0.15%. The number and percentage of fetuses malformed per litter(open eye, exophthalmia, exen-cephaly, short, constricted, orno tail, major vessel malformations, fused or branched ribs,and fused or misaligned thoracic vertebral centra) were elevatedat 0.05,0.10, and 0.15% DEHP. In conclusion, DEHP was not teratogenicat any dose tested in Fischer 344 rats when administered inthe feed throughout gestation but did produce maternal and otherembryofetal toxicity at 1.0, 1.5, and 2.0%. In contrast, DEHPadministration throughout gestation in CD-I mice resulted inan increased incidence of malformations at doses which producedmaternal and other embryofetal toxicity (0.10 and 0.15%) andat a dose (0.057percnt;) which did not produce significant maternaltoxicity. No treatment-related embryofetal toxicity includingteratogenicity was observed in mice at 0.025% Or in rats at0.5% DEHP.     

Developmental Toxicity Studies in Mice, Rats, and Rabbits with the Anticonvulsant Gabapentin

The developmental toxicity of the anticonvulsant agent gabapentinwas evaluated in mice, rats, and rabbits treated by gavage throughoutorganogenesis. Mice received 500, 1000, or 3000 mg/kg on gestationdays (GD) 6–15 and rats and rabbits received 60, 300,or 1500 mg/kg on GD 6–15 (rats) or 6–18 (rabbits).Additional groups received an equivalent volume of the vehicle,0.8% methylcellulose, or remained untreated. All dams were observeddaily for clinical signs of toxicity. In mice, body weightsand food consumption were recorded on GD 0, 6, 12, 15, and 18while in rats and rabbits these parameters were evaluated daily.Near term (mouse, GD 18; rat, GD 20; and rabbit, GD 29) eachfemale was euthanatized, necropsies were performed, and litterand fetal data were collected. Live fetuses were examined forexternal, visceral, and skeletal variations and malformations.No adverse maternal or fetal effects were observed in mice orrats given doses up to 1500 or 3000 mg/kg, respectively. Notreatment-related maternal or fetal effects were apparent inrabbits given 60 or 300 mg/kg. At 1500 mg/kg, one rabbit died,four others aborted, and reduced food consumption and body weightgain were observed. No other reproductive, litter, or fetalparameters were affected, except that the incidence of visceralvariations in rat fetuses was slightly but statistically significantlyincreased at 1500 mg/kg due to a slight increase in the incidenceof dilated renal pelvis. This finding was not considered biologicallysignificant because this degree of variability has been seenin this strain of rats. In conclusion, no evidence of teratogenicitywas found for gabapentin at doses up to 3000 mg/kg in the mouseand up to 1500 mg/kg in the rat and rabbit.     

The Development Toxicity of 2-Ethylhexanoic Acid in Wistar Rats

The developmental toxicity of 2-ethylhexanoic acid (2-EHA),a wood preservative and a mammalian metabolite of di-(2-ethylhexyl)phthalatewas examined in Wistar rats (20–21 pregnant females/dose).Mated animals were exposed to 2-EHA in their drinking waterat doses of 100, 300, or 600 mg/kg/day on Days 6–19 ofgestation. Control animals received vehicle water. The fetuseswere examined (on Gestational Day 20) for external, visceral,and skeletal malformations and variations. 2-EHA was marginallytoxic to the dams at 600 mg/kg, but not at lower doses, sincethe mean near term body weight was reduced by 11%. This doselevel was also slightly fetotoxic as indicated by a 5 to 8%decrease in the mean fetal body weight both in males and females.No treatment-related effects were observed in the number ofimplantations or live fetuses. At doses of 100 mg/kg and above,2-EHA caused skeletal malformations (clubfoot, absence of fibula,polydactyly), while the development of visceral tissues wasless affected. The number of affected fetuses increased in adose-dependent way (4.9, 8.9, and 15.3% of treated offspringat 100, 300, and 600 mg/kg/day, respectively, vs 2.4% control).These results indicate that 2-EHA is teratogenic in rats alreadyat doses which are not yet maternally toxic. The skeleton appearsto be the main target of 2-EHA in developing rats.     

Developmental toxicity studies of 2-(difluoromethyl)-dl-ornithine (DFMO) in rats and rabbits.

DFMO, an irreversible inhibitor of ornithine decarboxylase (ODC), is under development as a chemopreventive drug against cancers with pronounced proliferative phases. In support of human clinical trials, preclinical developmental toxicity studies were conducted in pregnant rats and rabbits. Rats were treated during GD 6-17, and fetuses were obtained by C-section on GD 20. Rabbits were treated during GD 7-20, and fetuses were obtained by C-section on GD 29. The dose range-finding study in rats (5/group at 0, 50, 125, 300, 800, or 1000 mg/kg/day) revealed maternal toxicity at doses > or = 800 mg/kg/day (decreased body weights and food consumption) and developmental toxicity at doses > or = 300 mg/kg/day (increased early resorptions and reduced fetal body weights). In the main study, rats (25/group) received 0, 30, 80, or 200 mg/kg/day. Developmental toxicity in the absence of maternal toxicity was observed at 200 mg/kg/day as significantly decreased fetal weights and increased incidence of litters with skeletal variations of 14th rudimentary rib, 14th full rib, and/or 27th presacral vertebrae. There were no treatment-related fetal skeletal malformations or external or visceral anomalies at any dose level. The dose range-finding study in rabbits (5/group at 0, 30, 60, 120, 240, or 500 mg/kg/day) revealed developmental toxicity at doses > or = 60 mg/kg/day (increased resorptions and reduced fetal body weights) in the absence of maternal toxicity. In the main study, rabbits (20/group) received 0, 15, 45, or 135 mg/kg/day. Developmental toxicity in the absence of maternal toxicity was observed at 135 mg/kg/day as nonsignificantly increased early resorptions, decreased implantation sites, decreased viable fetuses, and reduced fetal weights. There were no external, visceral, or skeletal anomalies at any dose level. Thus, in the main developmental toxicity studies, DFMO produced developmental but not maternal toxicity at 200 and 135 mg/kg/day in rats and rabbits, respectively. Accordingly, in rats, the maternal no-observable-effect level (NOEL) was 200 mg/kg/day and the fetal NOEL was 80 mg/kg/day; while in rabbits the maternal NOEL was 135 mg/kg/day and the fetal NOEL was 45 mg/kg/day. These fetal NOELs are several-fold higher than the dose level currently used in Phase II and III clinical trials (approximately 13 mg/kg).     

Developmental Toxicity Evaluation of Sodium Fluoride Administered to Rats and Rabbits in Drinking Water

Sodium fluoride (NaF; Cas No. 7681-49-4) is used in fluoridatingmunicipal water supplies, resulting in chronic exposure of millionsof people worldwide. Because of a lack of pertinent developmentaltoxicity studies in the literature, sodium fluoride was administeredad libitum in deionized/filtered drinking water (to mimic humanexposure) to Sprague-Dawley-derived rats (26/group) on GestationDays (GD) 6 through 15 at levels of 0, 50, 150, or 300 ppm andNew Zealand White rabbits (26/group) on GD 6 through 19 at levelsof 0, 100, 200, or 400 ppm. Higher concentrations via drinkingwater were not practicable due to the poor palatability of sodiumfluoride. Drinking water (vehicle) contained less than 0.6 ppmsodium fluoride (limit of detection) and sodium fluoride contentof the feed was 12.4 ppm fluoride (rats) and 15.6 ppm fluoride(rabbits). Maternal food, water, body weights, and clinicalsigns were recorded at regular intervals throughout these studies.Animals were killed on GD 20 (rats) or 30 (rabbits) and examinedfor implant status, fetal weight, sex, and morphological development.In the high-dose group of both studies there was an initialdecreased maternal body weight gain which recovered over timeand a decreased water consumption—attributed to decreasedpal atability. No clear clinical signs of toxicity were observed.Maternal exposure to sodium fluoride during organogenesis didnot significantly affect the frequency of postimplantation loss,mean fetal body weight/litter, or external, visceral or skeletalmalformations in either the rat or the rabbit. The NOAEL formaternal toxicity was 150 ppm sodium fluoride in drinking water({small tilde}18 mg/kg/day) for rats, and 200 ppm ({small tilde}18mg/kg/day) for rabbits. The NOAEL for developmental toxicitywas 300 ppm sodium fluoride ({small tilde}27 mg/kg/day) forrats and 400 ppm ({small tilde}29 mg/kg/day) for rabbits administeredduring organogenesis in drinking water. The total exposure tofluoride (mg F/kg body weight/day from food and drinking watercombined) in the mid- and high-dose groups for both specieswas >100-fold higher than the range at 0.014–0.08 mgF/kg/day estimated for a 70-kg person from food and fluoridated(1 ppm) drinking water.     

Developmental Toxicity Evaluation of Ethylene Glycol by Gavage in New Zealand White Rabbits

Artificially inseminated New Zealand white (NZW) rabbits wereadministered ethylene glycol (EG) by gavage on Gestational Days(GD) 6 through 19 at doses of 0, 100, 500, 1000, or 2000 mg/kg/day,with 23–24 inseminated animals per group. Clinical signswere recorded and water consumption was measured daily; doeswere weighed on GD 0, 6–19, 25, and 30. At necropsy (GD30), maternal liver, kidney, and gravid uterine weights wererecorded. Histopathologic examination was performed on kidneysfrom 10 does/dose and for all unscheduled deaths. Ovarian corporalutea were counted and uterine implantation sites (total sites,resorptions, dead and live fetuses) were recorded. All livefetuses were weighed, sexed, and examined for external, visceral,and skeletal malformations and variations. EG resulted in profoundmaternal toxicity at 2000 mg/kg/day (42% mortality; three earlydeliveries and one spontaneous abortion) associated with renalpathology and unaccompanied by any other indicators of maternaltoxicity. Renal lesions at 2000 mg/kg/day involved the corticalrenal tubules and included intraluminal oxalate crystals, epithelialnecrosis, and tubular dilatation and degeneration. No dose-relatedmaternal toxicity occurred at 100–1000 mg/kg/day. Therewas no indication of developmental toxicity at any dose tested,including no effects on pre- or postimplantation loss, numberof fetuses, fetal body weight, or sex ratio (% male fetuses)per litter, and no evidence of teratogenicity. The "no observableadverse effect level" (NOAEL) for maternal toxicity was therefore1000 mg/kg/day and the NOAEL for developmental toxicity wasat least 2000 mg/kg/day in this study. The sensitivity of NZWrabbits relative to that of Sprague—Dawley rats and Swissmice for maternal and developmental toxicity from gavage administrationof EG during organogenesis can be determined for maternal toxicity:rabbits>mice>rats, and for developmental toxicity, mice>>rats >> rabbits.     

Developmental Toxicity of CI-921, an Anilinoacridine Antitumor Agent

CI-921, an anilinoacridine compound active against leukemicand solid tumors, was evaluated for potential developmentaltoxicity. Intravenous injections of CI-921 in dextrose weregiven to female Sprague-Dawley rats (0.1, 0.5, and 1.0 mg/kg)on Gestation Days (GD) 6–15 and to female New ZealandWhite rabbits (0.1, 1.0 and 2.0 mg/kg) on GD 6–18. Appropriatevehicle and untreated controls were included. Maternal and fetalparameters, including external, visceral, and skeletal malformationsand variations, were assessed. Treatment of rats with 1.0 mg/kgresulted in maternal toxicity, manifested as reduced body weightgain and food consumption during and after treatment. Reducedfetal body weight, an increased incidence of stunted fetuses,malformations of the axial and appendicular skeleton, microphthalmia,and an increased number of anatomical variations (includinganomalies of the axial skeleton and apparent hydronephrosis)also occurred in rats at 1.0 mg/kg. Treatment of rabbits resultedin no apparent maternal toxicity. However, reduced fetal bodyweight, agenesis of the azygous lobe of the lung, and an increasedincidence of variations of the axial skeleton occurred at 2.0mg/kg in rabbits. These results indicate that CI-921, at thehighest dose tested in each species, produced developmentaltoxicity in the presence of maternal toxicity in rats, but inthe absence of maternal toxicity in rabbits.     

Reproductive toxicology of inhaled styrene oxide in rats and rabbits

Experiments were performed to evaluate reproductive and developmental toxicology in rats and rabbits exposed to styrene oxide by inhalation. Female rats were exposed to 100 or 300 ppm styrene oxide or to filtered air for 7 h/day, 5 days/week for 3 weeks. Extensive mortality occurred in rats that received prolonged exposure to 100 ppm styrene oxide while 300 ppm was rapidly lethal. As a result exposures were terminated in this latter group and the group was eliminated from further study. The rats of the 0 and 100 ppm groups were then mated and exposed to 0 or 100 ppm styrene oxide daily through 18 days of gestation (dg). Female rabbits were artificially inseminated and exposed for 7 h daily to 0, 15, or 50 ppm styrene oxide through 24 dg. Both of these lower concentrations used for exposure of the rabbits produced mortality of does. The rats were killed at 20 dg and the rabbits at 30 dg. Pregnant animals were examined for toxic changes including altered tissue weights and histopathologic effects. Litters were evaluated using several measures of embryotoxicity, and live fetuses were examined for external, visceral, and skeletal malformations. Exposure during gestation appeared to increase preimplantation loss in rats, and tended to increase the incidence of resorptions in rabbits. In both species, fetal weights and crown-rump lengths were reduced by gestational exposure. The incidences of ossification defects of the sternebrae aned occipital bones were increased by gestational exposure of rats to styrene oxide. These results indicate that inhalation exposures at these concentrations produce reproductive and development toxicity, as well as maternal toxicity.     

Oral meso-2,3-dimercaptosuccinic acid in pregnant Sprague-Dawley rats: teratogenicity and alterations in mineral metabolism. I. Teratological evaluation

meso-2,3-Dimercaptosuccinic acid (DMSA), an effective antagonist for the treatment of lead, arsenic, mercury, and cadmium poisoning, was evaluated for developmental toxicity in pregnant Sprague-Dawley rats. DMSA was administered by gavage on d 6-15 of gestation at doses of 0, 100, 300, or 1000 mg DMSA/kg/d. At termination on d 20 of gestation, fetuses were examined for external, visceral, and skeletal malformations and variations. Maternal toxicity was observed at all doses, as evidenced by a significant decrease in body weight gain. There were no effects with respect to hematology or clinical chemistry. Increased early resorptions, increased percentage postimplantation loss, and reduced fetal body weight per litter were observed at 100, 300, and 1000 mg/kg/d. Examination of fetuses for gross external abnormalities, visceral and skeletal malformations, or ossification variations revealed that DMSA did not produce teratogenicity at any dosage level. However, significant fetotoxicity was observed at 100, 300, and 1000 mg/kg/d. The no-observable-effect level (NOEL) for maternal and developmental toxicity was less than 100 mg DMSA/kg/d.     

Developmental Toxicity Evaluation of Acrylamide in Rats and Mice

Developmental Toxicity Evaluation of Acrylamide in Rats andMice. FIELD, E. A., PRICE, C. J., SLEET, R. B., MARR, M. C,MORRISSEY, R. E., AND SCHWETZ, B. A. (1990). Fundam. Appl. Toxicol.14, 502–512. Acrylamide (ACRL), a widely used industrialchemical with neurotoxic effects, was evaluated for developmentaltoxicity. ACRL in distilled water was administered once dailyby 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 highestdose as reduced body weight gain in both species and hindlimbsplaying in treated mice only. Weight gain corrected for graviduterine weight was also reduced in rats at 7.5 and 15 mg/kg/day.Embryo/fetal toxicity was not observed in rats, but fetal weightwas reduced in mice administered 45 mg/kg/day. No increase inthe incidence of malformations was observed in either species;however, the incidence of variations (predominately extra rib)increased with dose. In summary, administration of ACRL duringorganogene-sis produced maternal and developmental toxicityat 45 mg/kg/day in mice and maternal, but not developmental,toxicity at doses 7.5 mg/kg/day in rats.     

Evaluation of the Developmental Toxicity of Ethylene Glycol Aerosol in the CD Rat and CD-1 Mouse by Whole-Body Exposure

Ethylene glycol (EG) is a major industrial chemical, shown tobe teratogenic at high doses by gavage in rodents. Since oneroute of industrial exposure is to the aerosol at high concentrations,timed-pregnant CD rats and CD-1 mice were exposed, whole-body,to a respirable aerosol of EG (mass median aerodynamic diameter,2.3 µm) on Gestational Days (GD) 6 through 15 for 6 hrper day at target exposure concentrations of 0, 150, 1000, or2500 mg/m³ (analytical concentrations of 0, 119 ± 13,888 ± 149, and 2090 ± 244 mg/m³, respectively),with 25 plug-positive animals per species per group. Clinicalobservations and maternal body weights were documented throughoutgestation for both species. Maternal food and water consumptionwas measured in rats only throughout gestation. At schedulednecropsy (GD 21 for rats, GD 18 for mice), maternal animalswere evaluated for body weight, liver weight, kidney weight,gravid uterine weight, number of ovarian corpora lutea, andstatus of implantation sites, i.e., resorptions, dead fetuses,live fetuses. Fetuses were dissected from the uterus, counted,weighed, sexed, and examined for external, visceral, and skeletalmalformations and variations. All rat dams survived to scheduledtermination. Minimal maternal toxicity was indicated by a significantincrease in absolute and relative liver weight at 2500 mg/m³.Food and water consumption, maternal body weights and weightgain, and maternal organ weights (other than liver) were unaffectedby exposure. Gestational parameters were unaffected by exposure,including pre- and post-implantation loss, live fetuses/litter,sex ratio, and fetal body weight/litter. There was no treatment-relatedincrease in the incidence of any individual malformation, inthe incidence of pooled external, visceral, or skeletal malformations,or in the incidence of total malformations by fetus or by litter.There were no increases in the incidence of external or visceralvariations. Evidence of fetotoxicity, expressed as reduced ossificationin the humerus, the zygomatic arch, and the metatarsals andproximal phalanges of the hind-limb, was observed at 1000 and2500 mg/m³. All mouse dams survived to scheduled termination.One dam at 2500 mg/m³ was carrying a totally resorbed litterat termination. Maternal toxicity was observed at 1000 and 2500mg/m³, expressed as reduced body weight and weight gain duringand after the exposure period, and reduced gravid uterine weight.(Maternal effects may have been due, in part or in whole, toeffects on the conceptuses; see below.) Embryo/fetal toxicitywas also observed at 1000 and 2500 mg/m³, expressed as an increasein nonviable implantations/litter, a reduction in viable implantations/litter,and reduced fetal body weights (male, female, and total)/litter.The incidences of individual and pooled external, visceral,and skeletal malformations were increased at 1000 and 2500 mg/m³,as was the incidence of total malformations. Malformations werefound in the head (exencephaly), face (cleft palate, foreshortenedand abnormal face, and abnormal facial bones), and skeleton(vertebral fusions, and fused, forked, and missing ribs). Theincidences of many fetal variations were also increased at 1000and 2500 mg/m³ (and only a few at 150 mg/m³). The no observableadverse effect level (NOAEL) for maternal toxicity in rats was1000 mg/m³ (analytical concentration 888 mg/m³) and in micewas 150 mg/m³ (analytical concentration 119 mg/m³). The NOAELfor development toxicity in rats was 150 mg/m³ and in mice wasat or below 150 mg/m³, under the conditions of this study. Analysisof EG on the fur of rats and mice during and after the exposureperiod at 2500 mg/m³ indicated that much of the EG "dose" (65–95%)was potentially derived from ingestion after grooming and/orpercutaneous absorption. This contribution of the ingested and/orabsorbed chemical could have been sufficient, per se, to producethe teratogenic effects observed in mice. The definitive evaluationof the possible role of inhaled EG aerosol alone in teratogenesisrequires an exposure regimen which limits or precludes exposureby any other route.     

Developmental Toxicity of Dimethylacetamide by Inhalation in the Rat

Developmental Toxicity of Dimethylacetamide by Inhalation inthe Rat. SOLOMON, H. M., FERENZ, R. L., KENNEDY, G. L., ANDSTAPLES, R. E. (1991). Fundam. Appl. Toxicol. 16, 414–422.Dimethylacetamide (DMAC) is a widely used industrial solvent.It has been reported to be teratogenic when given to rats byinjection or following dermal application. Most of these studiesemployed large single doses and did not examine both the fetaland the maternal response. In this study, groups of pregnantCrl:CD rats were exposed to 32, 100, or 282 ppm DMAC by inhalationfor 6 hr/day from Days 6 through 15 of gestation (day on whichcopulation plug was detected was termed Day 1G). A control groupof chambered pregnant rats was exposed simultaneously to aironly. All female rats were euthanized on Day 21G. At 282 ppm,both maternal weight gain during the exposure period and fetalweight were significantly decreased and accompanied by a significantdose-response trend. These effects were not seen in rats inhalingeither 32 or 100 ppm. Fetal resorptions were not increased inany of the groups exposed to DMAC. Fetal incidences of external,visceral, or skeletal variations and malformations were similarbetween the test and control groups. Therefore, both fetal andmaternal toxicity were noted at 282 ppm and the no-observedadverse-effect level under these experimental conditions was100 ppm for both the dam and the conceptus. DMAC was not demonstratedto produce malformations in the rat fetus even at a level thatwas toxic to the dam.     

Developmental toxicities of methacrylic acid, ethyl methacrylate, n-butyl methacrylate, and allyl methacrylate in rats following inhalation exposure.

The developmental toxicities of 4 methacrylates were studied in Sprague-Dawley rats after inhalation exposure for 6 h/day, during days 6 to 20 of gestation. The exposure concentrations were, for methacrylic acid, 0, 50, 100, 200, or 300 ppm; for ethyl methacrylate, 0, 600, 1200, 1800, or 2400 ppm; for n-butyl methacrylate, 0, 100, 300, 600, or 1200 ppm; and for allyl methacrylate, 0, 12, 25, 50, or 100 ppm. No significant increases in embryo/fetal lethality or fetal malformations were observed after exposure to any of these methacrylates. Fetal toxicity evidenced by statistically significant decreases in fetal body weights was observed at exposure levels > or = 1200 ppm ethyl methacrylate, > or = 600 ppm n-butyl methacrylate, and at 100 ppm allyl methacrylate. Statistically significant increases in the incidence of fetuses with skeletal variations and of fetuses with any variations were noted at 1200 ppm n-butyl methacrylate. These developmental effects were observed in the presence of overt signs of maternal toxicity. While maternal toxicity was observed, methacrylic acid caused no evidence of developmental toxicity up to 300 ppm.     

Embryo lethality and teratogenicity of a new fluoroquinolone antibacterial DW-116 in rats

DW-116, 1-(5-fluoro-2-pyridyl)-6-fluoro-7-(4-methyl-l-piperazinyl)-1, 4-dihydro-4-oxoquinolone-3-carboxylic acid hydrochloride, is a newly developed fluoroquinolone antibacterial. The potential of DW-116 to induce developmental toxicity was investigated in Sprague-Dawley rats. DW-116 was administered by gavage to pregnant rats from days 6 to 16 of gestation at dose levels of 0, 31.3, 125, and 500 mg/kg per day. All dams were subjected to caesarean section on day 20 of gestation and their fetuses were examined for external, visceral and skeletal abnormalities. At 500 mg/kg, toxic effects including clinical signs of toxicity, suppressed body weight and decreased food intake were found in dams. An increase in the resorption rate, a decrease in the litter size, a reduction in the fetal weight, and a decrease in the placental weight were also seen. In addition, various types of external, visceral, and skeletal malformations occurred at an incidence of 17.9, 74.2 and 8.3%, respectively. Characteristic malformations included oedema, cleft palate, dilated cerebral ventricle, hypoplasia of lung and ventricular septum defect. A dramatic increase in the incidence of skeletal variations (55.6%) and retardations (94.4%) and a decrease in the number of ossification centres of sternebra, metacarpals, metatarsals and sacrocaudal vertebra were also observed. At 125 mg/kg, a reduction in the placental weight and an increase in the incidence of skeletal variations were found. There were no signs of maternal toxicity or embryotoxicity at 31.3 mg/kg. These results indicate that the fluoroquinolone antibacterial DW-116 is embryotoxic and teratogenic at minimally maternally toxic dose and is minimally embryotoxic at nonmaternally toxic dose in rats. Received: 4 November 1999 / Accepted: 23 December 1999     

Codeine: Developmental Toxicity in Hamsters and Mice

Codeine: Developmental Toxicity in Hamsters and Mice. Williams,J., PRICE, C. J., SLEET, R. B., GEORGE, J. D., MARR, M. C, KIMMEL,C. A., AND MORRISSEY, R. E. (1991). Fundam. Appl. Toxicol. 16,401–413. Timed-pregnant LVG Syrian hamsters and SwissCD-I mice were dosed orally twice daily (b.i.d.) with codeinein water on Gestational Days (gd) 5–13 (0, 10, 50, or150 mg/kg, b.i.d.—hamsters) or 6–15 (0, 37.5, 75,150, or 300 mg/kg, b.i.d.—mice). Dams were necropsiedon gd 14 (hamsters) or 17 (mice), and fetuses were weighed,sexed, and examined for external, visceral, and skeletal malformations.No maternal deaths were observed in hamsters, while 19% of thepregnant mice in the high-dose group died. Maternal weight gain(gestational and treatment periods) and gravid uterine weightswere significantly depressed in hamsters (150 mg/kg, b.i.d.)and in mice (300 mg/kg, b.i.d.). However, the corrected weightgain for both species, although decreased, was not significantlydifferent from that of the controls. In both species, maternalliver weights (relative) were significantly increased in thehigh-dose groups. There were increases in the percentage resorptionsper pregnant dam and in the proportion of litters with 100%resorptions in the high-dose groups of both species. Consideringonly live litters, the number of live fetuses per litter andthe sex ratio were unaffected in both species. Mean fetal bodyweights were also significantly decreased in the 50 and 150mg/kg, b.i.d. (hamsters), and the 150 and 300 mg/kg, b.i.d.(mice), groups. The no-observed-adverse-effect levels (NOAELs)for developmental toxicity were 10 (hamsters) and 75 (mice)mg/kg, b.i.d., whereas the NOAELs for maternal toxicity were50 (hamsters) and 150 (mice) mg/kg, b.i.d. The predominant structuralmalformation in hamsters was meningoencephalocele (high-dosegroup only), affecting 3% of fetuses and 19% of litters (neitherstatistically significant). Codeine did not induce any increasein structural malformations in mice. Thus, codeine produceddevelopmental toxicity (as indicated by decreased fetal bodyweight) at doses below those producing maternal toxicity inboth hamsters and mice. In the hamster, the more sensitive speciesto codeine developmental toxicity, effects were observed ata total daily dose of 100 mg/kg, which is only 11 times themaximum human therapeutic oral dose.