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 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.     

Evaluation of the Developmental Toxicity of Methacrylamide and N,N'-Methylenebisacrylamide in Swiss Mice

Timed-pregnant CD-1 outbred albino Swiss mice received eithermethacrylamlde (MAC; 0, 60, 120, or 180 mg/kg/day) or N,N'-methylenebisacrylamide(BAC; 0, 3, 10, or 30 mg/kg/day) po in distilled water on gestationaldays (GD) 6 through 17. Maternal clinical status was monitoreddaily. At termination (GD 17), confirmed-pregnant females (27–30per group, MAC; 24–25 per group, BAC) were evaluated forclinical status and gestational outcome; live fetuses were examinedfor external, visceral, and skeletal malformations. For MAC,no treatment-related maternal mortality was observed. Maternalbody weight on GD 17, maternal weight gain during treatmentand gestation, and corrected maternal weight gain were reducedat the high dose. Relative maternal food and water intake wasnot adversely affected; neurotoxicity was not observed. Relativematernal liver weight was increased at a 120 mg/kg/day; graviduterine weight was decreased at 180 mg/kg/day. The maternalno-observed adverse effect level (NOAEL) was 60 mg/kg/day. TheNOAEL for developmental toxicity was also 60 mg/kg/day. At 120 mg/kg/day, mean fetal body weight was reduced. At 180 mg/kg/day,increased postimplantation death per litter was observed. Morphologicaldevelopment was not affected. The maternal NOAEL for BAC was10 mg/kg/day. At 30 mg/kg/day, decreased maternal body weighton GD 17, maternal body weight change during treatment and gestation,corrected maternal body weight, and gravid uterine weight wereobserved. Relative maternal liver weight increased at 30 mg/kg/day.The developmental NOAEL was 3 mg/kg/day BAC. Mean fetal bodyweight was reduced at 30 mg/kg/day. At 10 mg/kg/day, an increasedincidence of fetal variations (extra rib) was observed, althoughfetal malformation rate was unaffected. MAC and BAC were notteratogenic to Swiss mice at the doses tested. BAC was morepotent than MAC in causing adverse maternal and developmentaleffects.     

Developmental toxicity assessment of arsenic acid in mice and rabbits

To evaluate potential effects of exposure to inorganic arsenic throughout major organogenesis, CD-1 mice and New Zealand White rabbits were gavaged with arsenic acid dosages of 0, 7.5, 24, or 48 mg/kg/d on gestation days (GD) 6 through 15 (mice) or 0, 0.19, 0.75, or 3.0 mg/kg/d on GD 6 through 18 (rabbits) and examined at sacrifice (GD 18, mice; GD 29, rabbits) for evidence of toxicity. Two high-dose mice died, and survivors at the high and intermediate doses had decreased weight gains. High-dose-group fetal weights were decreased; no significant decreases in fetal weight or increases in prenatal mortality were seen at other dosages. Similar incidences of malformations occurred in all groups of mice, including controls. At the high dose in rabbits, seven does died or became moribund, and prenatal mortality was increased; surviving does had signs of toxicity, including decreased body weight. Does given lower doses appeared unaffected. Fetal weights were unaffected by treatment, and there were no effects at other doses. These data revealed an absence of dose-related effects in both species at arsenic exposures that were not maternally toxic. In mice, 7.5 mg/kg/d was the maternal No-Observed-Adverse-Effect-Level (NOAEL); the developmental toxicity NOAEL, while less well defined, was judged to be 7.5 mg/kg/d. In rabbits, 0.75 mg/kg/d was the NOAEL for both maternal and developmental toxicity.     

Absence of embryo-fetal toxicity in rats or rabbits following oral dosing with nelfinavir

The potential for nelfinavir mesylate (VIRACEPT) to induce maternal and embryo-fetal toxicity was evaluated in rats and rabbits following oral administration. The drug was administered by gavage to rats at doses of 200, 500, or 1000mg/kg/day on days 6-17 of gestation and to rabbits at doses of 200, 400, or 1000mg/kg/day on days 7-20 of gestation. Dams and does were euthanized on GD20 and 29, respectively, and the offspring were weighed and examined for external, visceral, and skeletal alterations. Maximum plasma nelfinavir concentrations (C(max)) in rats were comparable to C(max) values in humans and were 3- to 6-fold higher than the reported human trough levels, while plasma nelfinavir levels in rabbits were approximately 0.13-0.17x the human C(max) and 0.25-0.5x the human trough. In rats, no treatment-related maternal or embryo-fetal toxicity was observed at any dose level and the NOAEL for both maternal and fetal toxicity was considered to be 1000mg/kg/day. Two rabbits in the 400mg/kg/day group died prior to scheduled termination. Because no deaths occurred in the high dose group and there were no other treatment-related signs of clinical toxicity in any dose group, these deaths were considered unrelated to nelfinavir. Group mean body weight loss in rabbits was observed at 1000mg/kg/day on gestation days 7-10. Food consumption was also reduced in this treatment group throughout the dosing period. There were no treatment-related findings in other maternal or fetal parameters. Thus, the no-observed-adverse-effect-level (NOAEL) for maternal toxicity in the rabbit was considered to be 400mg/kg/day (based on maternal body weight loss in the high dose group), while the NOAEL for embryo-fetal toxicity in the rabbit was considered to be 1000mg/kg/day. Thus, under the conditions of this study, nelfinavir was not considered to be toxic to the rat or rabbit conceptus.     

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.     

The Developmental Toxicity of Ethylene Glycol Diethyl Ether in Mice and Rabbits

Timed-pregnant CD-1 outbred Albino Swiss mice and New ZealandWhite rabbits were dosed by gavage with ethylene glycol diethylether (EGdiEE) in distilled water during major organogenesis.Mice were dosed on Gestational Days (gd) 6 through 15 (0, 50,150, 500, or 1000 mg/kg/day) and rabbits on gd 6 through 19(0, 25, 50, or 100 mg/kg/day). Maternal clinical status wasmonitored daily during treatment. At termination (gd 17, mice;gd 30, rabbits), confirmed-pregnant females (22–24 pergroup, mice; 26–32 per group, rabbits) were evaluatedfor clinical status and gestational outcome; each live fetuswas examined for external, visceral, and skeletal malformations.In mice, no maternal mortality was observed, but maternal bodyweight gain during gestation and treatment, and at terminationwas reduced at 1000 mg/kg/day. The reduction of maternal bodyweight gain during gestation was secondary to embryo/fetal toxicity,i.e., reduced gravid uterine weight as a consequence of decreasedlitter size and fetal weight. The no-observed adverse effectlevel (NOAEL) for developmental toxicity was 50 mg/kg/day. At150 mg/kg/day the number of litters of mice with malformed fetuseswas increased. At 500 mg/kg/day fetal body weight was reduced,and malformation incidence was significantly increased. Exencephalyand fused ribs were observed most often. In rabbits, maternalbody weight was unaffected by treatment even though 6% maternalmortality was observed at 100 mg/kg/day. The developmental NOAELwas 25 mg/kg/day. Malformations were increased at 50 mg/kg/day,short tail, small spleen, fused sternebrae, and fused rib cartilagewere observed most often. In summary, oral administration ofEGdiEE to mice and rabbits during organogenesis produced profoundadverse developmental effects even in the absence of significantmaternal toxicity. Developmental effects in rabbits were morevaried.     

Evaluation of the Developmental Toxicity of Methacrylonitrile in Sprague-Dawley Rats and New Zealand White Rabbits

Timed-pregnant Sprague-Dawley (CD) outbred rats and New ZealandWhite rabbits were dosed by gavage with methacrylonitrile (MACR)in distilled water during major organogenesis. Rats were dosedon Gestational Days (GD) 6 through 15 (0, 5, 25, or 50 mg MACR/kg/day)and rabbits on GD 6 through 19 (0, 1, 3, or 5 mg MACR/kg/day).Maternal clinical status was monitored daily during treatment.At termination (GD 20, rats; GD 30, rabbits), confirmed-pregnantfemales (25–26 per group, rats; 17–22 per group,rabbits) were evaluated for clinical status and gestationaloutcome; each live fetus was examined for external, visceral,and skeletal malformations. In rats, no treatment-related maternalclinical signs or mortality were observed, nor was there anyadverse effect on maternal body weight or food or water consumption.At necropsy, absolute, relative, and adjusted maternal liverweight was increased at the mid- and high-dose groups, an effectthat may be indicative of induction of hepatic enzymes ratherthan toxicity. In the absence of any indication of maternaltoxicity, the no-observed-adverse-effect level (NOAEL) for maternaltoxicity in this study was 50 mg MACR/kg/day. The NOAEL fordevelop mental toxicity in rats was also 50 mg MACR/kg/day.There was no effect of treatment on postimplantation loss, meanfetal body weight per litter, or morphological development.In rabbits, maternal mortality and clinical signs were not doserelated. Maternal food consumption, body weight, and liver weightwere not adversely affected by treatment. Thus, the maternalNOAEL was 5 mg MACR/kg/day. Maternal toxicity, including death,was observed 7.5 mg/kg/day in preliminary studies. The developmentalNOAEL was also 5 mg MACR/kg/day. There was no adverse effectof treatment on postimplantation loss or fetal body weight.A significant decrease in the percentage male fetuses per litterwas observed, although there was no effect on total live littersize, suggesting that the reduction in the ratio of live malefetuses in the high-dose group was not biologically significant.MACR had no adverse effect on morphological development. Insummary, oral administration of MACR to rats and rabbits duringorganogenesis, at doses that did not cause persistent maternaltoxicity (50 mg MACR/kg/day, rats; 5 mg MACR/kg/day, rabbits),also did not cause any adverse developmental effects.     

Developmental toxicity evaluation of 1,2,3,4-butanetetracarboxylic acid in Sprague Dawley (CD) rats

1,2,3,4-butanetetracarboxylic acid (BTCA), proposed as a formaldehyde substitute in the treatment of permanent press fabrics, was evaluated for developmental toxicity. Timed-mated CD rats (25 per group) received BTCA 250, 500, or 1000 mg/kg/day or vehicle (deionized/distilled water) by gavage on gestational days (gd) 6 through 19. Maternal feed and water consumption, body weight, and clinical signs were monitored throughout gestation. At termination (gd 20), confirmed-pregnant females (21 to 25 per group) were evaluated for clinical status and gestational outcome; live fetuses were examined for external, visceral, and skeletal malformations. One maternal death, reduced body weight, and reduced weight gain were noted at the high dose; confirmed pregnancy rates were 84 to 100% for each group. There were no treatment-related effects on fetal growth, survival, or morphologic development. The maternal toxicity NOAEL and LOAEL are 500 and 1000 mg/kg/day, respectively. The developmental toxicity NOAEL is > or = 1000 mg/kg/day, and the LOAEL was not established in this study.     

Effects of prenatal exposure to the environmental pollutant 2-bromopropane on embryo-fetal development in rats

2-Bromopropane (2-BP), a halogenated propane analogue, is a substitute for chlorofluorocarbones. The present study was carried out to investigate the potential adverse effects of 2-BP on pregnant dams and embryo-fetal development after maternal exposure on gestational days (GD) 6 through 19 in Sprague-Dawley rats. The test chemical was administered subcutaneously to pregnant rats at dose levels of 0, 250, 500, and 1000 mg/kg per day. All dams were subjected to caesarean section on GD 20 and their fetuses were examined for external, visceral and skeletal abnormalities. In the 1000 mg/kg group, maternal toxicity included an increase in the incidence of abnormal clinical signs, a suppression in the body weight and body weight gain, and a decrease in the food intake. Developmental toxicity included an increase in the fetal deaths, a decrease in the litter size, and a reduction in the fetal body weight. In addition, an increase in the incidence of fetal external, visceral, and skeletal abnormalities was seen. In the 500 mg/kg group, minimal developmental toxicity including decreased fetal body weight and increased fetal ossification delay was observed. There were no adverse effects on either pregnant dams or embryo-fetal development in the 250 mg/kg group. These findings suggest that a 14-day subcutaneous dose of 2-BP is embryotoxic and teratogenic at a maternally toxic dose (i.e., 1000 mg/kg per day) and is minimally embryotoxic at a nonmaternally toxic dose (i.e., 500 mg/kg per day) in Sprague-Dawley rats. In the present experimental conditions, the no-observed-adverse-effect level (NOAEL) of 2-BP is considered to be 500 mg/kg per day for dams and 250 mg/kg per day for embryo-fetal development.     

Developmental Toxicology Studies of Fluoxetine Hydrochloride Administered Orally to Rats and Rabbits

Pregnant Fischer 344 rats were given fluoxetine orally at doselevels of 0, 2, 5, or 12.5 mg/kg on Gestation Days (GD) 6–15;pregnant Dutch Belted rabbits were given 0, 2.5, 7.5, or 15mg/kg orally on GD 6–18. Cesarean sections were performedon rats and rabbits on GD 20 and 28, respectively. In rats,maternal toxicity was indicated at 12.5 mg/kg by depressionof weight gain and food consumption. Fetal viability, weight,and morphology were not affected at any dose level. Maternaland developmental No Observed Adverse Effect Levels (NOAELs)in the rat were 5 and 12.5 mg/kg, respectively. In rabbits,weight loss occurred at 2.5,7.5, and 15 mg/kg. Food consumptionwas also depressed at 7.5 and 15 mg/kg; abortions and maternalmortality occurred secondarily to anorexia and cachexia at 15mg/kg. Fetal viability, weight, and morphology were not affectedat any dose level. A NOAEL for maternal effects was not establishedin the rabbit; the NOAEL for developmental effects in the rabbitwas 15 mg/kg. Based on these data, fluoxetine did not exhibitany toxicity toward the developing rat or rabbit conceptus atdoses that were maternally toxic.     

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.     

Oral developmental toxicity study of methylsulfonylmethane in rats.

Methylsulfonylmethane (MSM) is a metabolite of dimethyl sulfoxide, and occurs naturally at low levels in many foods. MSM has received wide attention as a dietary supplement to promote joint health. The objective of these studies was to determine the developmental toxicity potential of MSM when administered orally to pregnant rats during the period of major organogenesis and histogenesis. In a preliminary dose-finding study, distilled MSM microprill (i.e., microspherical pellets of MSM) was administered by oral gavage at dose levels of 0 (vehicle control), 50, 250, 500, and 1000 mg/kg/day to 8-9 sperm-positive female Sprague-Dawley rats/group/day on gestation days 6-20. No evidence of maternal or fetal toxicity was observed. For the definitive developmental study, four groups of 24-25 timed-bred primiparous female rats were administered 0, 50, 500, or 1000 mg MSM/kg/day via gavage on gestation days 6-20. Maternal feed consumption, body weight, body weight gain, uterus weight and corrected body weight/body weight gain were unaffected by treatment. No evidence of maternal toxicity, and no significant differences in litter viability, litter size, or litter body weight were detected. Fetal evaluations failed to show any biologically significant increase in the incidence of anomalies in the MSM treated groups, and no malformations were seen in any of the fetuses. No evidence of fetal mortality, alterations to growth, or structural alterations were observed in the fetuses of dams administered 50-1000 mg/kg/day. Therefore, under the conditions of this study, the no-observed-adverse-effect level (NOAEL) for maternal and developmental toxicity was 1000 mg/kg/day.     

Developmental toxicity of di-(C(7)-C(9) alkyl) phthalate and di-(C(9)-C(11) alkyl) phthalate in the rat

Two phthalate esters, di-(C(7)-C(9) alkyl) phthalate (D79P) and di-(C(9)-C(11) alkyl) phthalate (D911P), have been assessed for their potential to cause developmental toxicity in the rat. Groups of 22 timed-mated Sprague-Dawley rats were administered 250, 500, or 1000 mg/kg D79P or D911P daily by oral gavage (5 ml/kg) between gestation days (GD) 1 and 19. Control animals received the vehicle (olive oil) alone. On GD20, the animals were sacrificed and the fetuses examined. Treatment resulted in no signs of maternal toxicity, as assessed by adjusted maternal bodyweight gain throughout gestation and clinical examinations, and no effects upon litter size, fetal survival or bodyweight. Pups of the high dose D79P and intermediate and high dose D911P groups showed increased incidences of supernumerary lumbar ribs. There was a significant increase in dilated renal pelves in pups of the low dose D79P and high dose D911P groups, but only for D911P was there a significant trend. Consequently, the no observed adverse effect level (NOAEL) for maternal toxicity for both D79P and D911P is 1000 mg/kg/day. The NOAEL values for developmental toxicity are 500 mg/kg/day D79P and 250 mg/kg/day D911P.     

Maternal and developmental toxicity study of sodium azide in rats

Sodium azide (NaN(3)) is being proposed for use as an active ingredient to control a broad spectrum of soil borne pathogens including insects, weeds, nematodes, fungi, and bacteria. The purpose of this study was to determine the maternal and developmental toxicity of NaN(3) in rats. Sperm-positive Sprague-Dawley rats were treated with NaN(3) via oral gavage once daily from Gestation Day (GD) 6 through 19 at respective dose levels of 0, 1, 5, and 17.5mg/kg/day. From GD 10-12, the high-dose was reduced to 10mg/kg/day due to maternal mortality. Cesarean section was performed on GD 20 and implantation and resorptions sites, live and dead fetuses were counted. Fetuses were weighed, sexed externally and processed for gross external, visceral and skeletal examinations. A high rate of maternal mortality; reduced gestation body weight, gestation body weight changes and food consumption; decreased corrected body weight and corrected weight gain were observed at 17.5/10mg/kg/day. Fetal weight was also reduced at 17.5/10mg/kg/day. There were no maternal deaths, clinical signs or body weight effects that were considered related to NaN(3) at 1 and 5mg/kg/day. No increase in the incidence of malformations and variations were observed at any of the doses evaluated. Based on the results of this study, the No Observed Adverse Effect Level (NOAEL) and the Lowest Observed Adverse Effect Level (LOAEL) for maternal and developmental toxicity of NaN(3) in rats were considered to be 5 and 17.5/10mg/kg/day, respectively.     

“Simulated gastric hydrolysis and developmental toxicity of dioctyltin bis(2-Ethylhexylthioglycolate) [DOTE] in rabbits and mice”

Based on previous studies, dioctyltin dichloride [DOTC] was a putative toxophore for dioctyltin thioesters. Our results, generated with the use of ¹¹⁹Sn-NMR spectroscopy demonstrated that dioctyltin bis(2-ethylhexyl thioglycolate) [DOTE] hydrolyzed to form dioctyltin chloro-(2-ethylhexyl thioglycolate) [DOTCE] under simulated gastric conditions, but no DOTC was formed. DOTE was administered orally at 4, 20, and 80 mg/kg/day [GD6-GD28; rabbits] or at 15, 30, and 60 mg/kg/day [GD5-GD17; mice]. There were no maternal deaths, treatment-related statistically significant reductions in maternal body weight or weight gain, or adverse gestational outcomes in either species. Maternal thymus weight was significantly reduced in mice at 30 and 60 mg/kg. There were no effects on fetal growth, no dose-dependent pattern of external, visceral or skeletal malformations and no increase in anatomical variations in either species. We conclude that DOTE likely forms DOTCE, not DOTC, in the stomach and DOTE was not teratogenic or fetotoxic in rabbits or mice. The rabbit maternal NOAEL was 80 mg/kg/day. The rabbit developmental NOAEL was 80 mg/kg/day. The mouse maternal LOAEL was 30 mg/kg/day based on reduced thymus weight and a dose-dependent effect on maternal weight at 60 mg/kg. The mouse developmental NOAEL was 60 mg/kg bw/day, the high dose.     

Higher susceptibility of newborn than young rats to 3-methylphenol

To determine susceptibility of infants to 3-methylphenol, a repeated dose toxicity study was conducted with oral administration to newborn and young rats. In an 18-day newborn study from postnatal days 4 to 21 at doses of 30, 100 and 300 mg/kg/day, various clinical signs including deep respiration, hypersensitivity on handling and tremors under contact stimulus, and depressed body weight gain were observed at 300 mg/kg. At 100 mg/kg, hypersensitivity and tremors were also noted in a small number of males only on single days during the dosing period. No adverse effects were observed in the 30 mg/kg group. There were no abnormalities of physical development, sexual maturation and reflex ontogeny. The no observed adverse effect level (NOAEL) for newborn rats was considered to be 30 mg/kg/day and the unequivocally toxic level 300 mg/kg/day. In a 28-day study starting at 5 weeks of age, clinical signs and depression of body weight gain, as observed in the newborn rats, appeared in both sexes at 1000 mg/kg but not 300 mg/kg. The NOAEL and the unequivocally toxic level were 300 mg/kg/day and 1,000 mg/kg/day, respectively. From these results, newborn rats were concluded to be 3 to 10 times more susceptible to 3-methylphenol than young rats. However, the realistic no adverse effect dose for the newborn must be slightly lower than 100 mg/kg/day, at which the toxicity incidence was very low, rather than 30 mg/kg/day. Based on this speculation and the equal toxicity at unequivocally toxic levels, the differences in the susceptibility to 3-methylphenol could be concluded to be 3 to 4 times. This is consistent with the results of our previous comparative studies on 4-nitrophenol, 2,4-dinitrophenol and 3-aminophenol, which showed 2 to 4 times differences in the susceptibility between newborn and young rats.     

Maternal and developmental toxicity evaluation of melatonin administered orally to pregnant Sprague-Dawley rats.

Melatonin (MEL) is a widely used, over-the-counter sleep aid, and it has putative contraceptive, antioxidant, antiaging, and anticancer effects. The developmental toxicity potential for repeated oral doses of MEL had not previously been evaluated. In the present studies, time-mated, Sprague-Dawley-derived (CD) rats were administered MEL or vehicle by gavage on gestation days (gd) 6-19. MEL-treated groups received 1-, 10-, 100-, 150-, or 200-mg/kg body weight/day in the screening study (15 rats/group), and 50, 100, or 200 mg/kg/day in the definitive study (25 rats/group). In both studies, maternal food/water consumption, body weight, and clinical signs were monitored at regular intervals throughout gestation. At termination (gd 20, both studies), maternal liver and gravid uterine weights, number of ovarian corpora lutea, conceptus survival, fetal sex, and fetal body weight were evaluated. Fetal morphological examination included external structures (both studies) as well as visceral and skeletal structures (definitive study). In the screening study, maternal serum levels of 17beta-estradiol, progesterone, prolactin, and luteinizing hormone were determined by radioimmunoassay, and mammary tissue was fixed, stained, and evaluated for percent glandular area within the fat pad. No maternal morbidity/mortality was found in either study. In the screening study, aversion to treatment (> or =100 mg/kg/day) and reduced maternal weight gain (> or =150 mg/kg/day) were noted, but reproductive/endocrine parameters and fetal development were not affected. In the definitive study, aversion to treatment was noted at > or =50 mg/kg/day, and mild sedation, reduced maternal food intake, and reduced body weight gain were found during initial treatment with 200 mg/kg/day. MEL had no effect on prenatal survival, fetal body weight, or incidences of fetal malformations/variations. Thus, in the definitive study, the maternal toxicity NOAEL and LOAEL were 100 and 200 mg/kg/day, respectively, and the developmental toxicity NOAEL was > or =200 mg/kg/day.     

Embryo-fetal development toxicity of prenatal exposure to penequine hydrochloride intramuscularly in rats.

The potential for penequine hydrochloride to induce maternal and embryo-fetal developmental toxicity was evaluated in Wistar rats. The drug was administered intramuscularly (i.m.) at dose levels of 0, 10, 30 or 50mg/kg/day to groups of pregnant rats from day 6 to 15 of gestation. All dams were observed for maternal body weights, food consumption and any abnormal change, and subjected to caesarean-section on gestation day (GD) 20; all fetuses obtained from caesarean-section were assessed by external inspection, visceral and skeletal examinations. In the 50mg/kg/day group, maternal toxicity included an increase in the incidence of abnormal clinical signs, and decrease in the body weight and body weight gain. Developmental toxicity included an increase in the postimplantation loss, a decrease in the litter size, and a reduction in the gravid uterus weight. In addition, a statistically non-significant increase in the incidence of fetal external, visceral, and skeletal alterations including malformations and variations were seen in high-dose group. There were no treatment-related findings in maternal clinical and intrauterine observations, and fetal morphological examinations in mid-, low-dose and control groups. Thus, under the conditions of this study, the no-observed-adverse-effect-level (NOAEL) and lowest-observed-adverse-effect-level (LOAEL) of penequine hydrochloride for both maternal and embryo-fetal toxicity in the Wistar rats were considered to be 30mg/kg/day and 50mg/kg/day, which are approximately 900 and 1500 above the therapeutic dosage, respectively.     

Evaluation of the developmental toxicity of formamide in New Zealand white rabbits.

Naturally mated female New Zealand White (NZW) rabbits (24/group) received formamide (35, 70, or 140 mg/kg/day) or vehicle (1 ml/kg deionized/distilled water) by gavage on gestational days (GD) 6 through 29. The study was conducted using a 2-replicate design. Maternal food consumption (absolute and relative), body weight, and clinical signs were monitored at regular intervals throughout gestation. One and four maternal deaths occurred at the low and high doses, respectively. Abortions or early deliveries were noted in 0, 2, 2, and 8 females in the 0, 35, 70, and 140-mg/kg/day dose groups, respectively. Other clinical signs associated with formamide exposure were minimal: primarily reduced or absent fecal output at the high dose (2-13 animals/day). Also at the high dose, maternal body weight was significantly depressed on GD 21, 24, and 27 (87-90% of the control value); maternal body weight gain was significantly reduced for GD 12 to 15, 18 to 21, and 21 to 24 (treated animals gained less than 1 g, or lost up to 100 g). In addition, maternal body weight gain was reduced at the middle dose for GD 18 to 21. Maternal body weight gain, corrected for gravid uterine weight, was unaffected. Relative maternal food consumption in the high-dose group was 34-59% of control intake from GD 12 through GD 24, but was comparable to controls thereafter. At termination (GD 30), confirmed-pregnant females (9-20 per group) were evaluated for clinical status, liver weights, and gestational outcome; live fetuses were examined for external, visceral, and skeletal malformations and variations. Maternal liver weight (absolute or relative to body weight) was unaffected by treatment, but gravid uterine weight at the high dose was 71% of the control value. A significantly increasing trend was noted for the percent non-live implants per litter. In addition, although not statistically significant from the control group, the values for the percent late fetal deaths per litter and percent non-live implants per litter in the 140-mg/kg/day group were higher than maximum historical values, suggesting an increase in late gestational deaths in the surviving high-dose animals. Formamide decreased the mean number of live fetuses per litter at the high dose to 66% of the control value. Mean fetal body weight per litter for males and the sexes combined was significantly decreased at the high dose; mean female fetal body weight was also decreased, although the difference did not reach statistical significance. There was no effect of treatment on the incidence of external, visceral, or skeletal malformations or variations in animals surviving to scheduled necropsy. In summary, the no-observed-adverse-effect level (NOAEL) for maternal toxicity was 70 mg/kg/day and the lowest-observed-adverse-effect level (LOAEL) was 140 mg/kg/day under the conditions of this study. Similarly, the NOAEL for developmental toxicity was 70 mg/kg/day and the LOAEL was 140 mg/kg/day.