Developmental toxicity assessment of the new fluoroquinolone antibacterial DW-116 in rabbits

DW-116 is a newly developed fluoroquinolone antibacterial with a broad spectrum against both Gram-positive and Gram-negative bacteria. We have reported recently that DW-116 is embryotoxic and teratogenic in rats. The present study was conducted to investigate the teratogenicity of DW-116, together with maternal toxicity and developmental toxicity using New Zealand White rabbits. The test chemical was administered by gavage to pregnant rabbits from gestational day (GD) 6 through to GD 18 at dose levels of 0, 5, 19.5 and 76.1 mg kg(-1) day(-1). All does were subjected to caesarean section on day 28 of gestation and their foetuses were examined for external, visceral and skeletal abnormalities. In the 76.1 mg kg(-1) group, a minimal maternal toxicity, as evidenced by decreased body weight gain during treatment period, was observed in pregnant rabbits. Significant embryo-foetal toxicity, including increased number of foetal deaths and delayed foetal ossification, was seen. However, no treatment-related morphological changes were detected in foetal external, visceral and skeletal examinations. There were no adverse effects on either pregnant dams or embryo-foetal development at 19.5 and 5 mg kg(-1). It was concluded that administration of DW-116 during the major organogenetic period in rabbits produced decreased maternal body weight gain, increased number of foetal deaths and foetal developmental delay but no evidence of teratogenicity. The no-observed-adverse-effect levels (NOAELs) of DW-116 are considered to be 19.5 mg kg(-1) day(-1) for does and embryo-foetuses, respectively.     

Evaluation of the prenatal developmental toxicity of orally administered arsenic trioxide in rats.

A thorough review of the literature revealed no published repeated-dose oral developmental toxicity studies of inorganic arsenic in rats. In the present study, which was conducted according to modern regulatory guidelines, arsenic trioxide was administered orally beginning 14 days prior to mating and continuing through mating and gestation until gestational day 19. Exposures began prior to mating in an attempt to achieve a steady state of arsenic in the bloodstream of dams prior to embryo-foetal development. Groups of 25 Crl:CD(SD)BR female rats received doses of 0, 1, 2.5, 5 or 10mg/kg/day by gavage. The selection of these dose levels was based on a preliminary range-finding study, in which excessive post-implantation loss and markedly decreased foetal weight occurred at doses of 15 mg/kg/day and maternal deaths occurred at higher doses. Maternal toxicity in the 10mg/kg/day group was evidenced by decreased food consumption and decreased net body weight gain during gestation, increased liver and kidney weights, and stomach abnormalities (adhesions and eroded areas). Transient decreases in food consumption in the 5mg/kg/day group caused the maternal no-observed-adverse-effect level (NOAEL) to be determined as 2. 5mg/kg/day. Intrauterine parameters were unaffected by arsenic trioxide. No treatment-related foetal malformations were noted in any dose group. Increased skeletal variations at 10mg/kg/day were attributed to reduced foetal weight at that dose level. The developmental NOAEL was thus 5mg/kg/day. Based on this study, orally administered arsenic trioxide cannot be considered to be a selective developmental toxicant (i.e. it is not more toxic to the conceptus than to the maternal organism), nor does it exhibit any propensity to cause neural tube defects, even at maternally toxic dose levels.     

Evaluation of the Pre-, Peri-, and Postnatal Toxicity of Monoethanolamine in Rats Following Repeated Oral Administration during Organogenesis

Pregnant Wistar rats (40/group) were administered monoethanolamine(MEA) as an aqueous solution by gavage at dose levels of 0,40, 120, and 450 mg/kg/day on days 6 through 15 of gestation.On day 20 of gestation, 25 dams/group were euthanized and thefetuses were delivered by cesarean section, weighed, sexed,and examined for external, visceral, and skeletal alterations.The remaining dams (15/group) were allowed to litter and reartheir pups to day 21 postpartum. The dams and pups were theneuthanized and examined for gross pathologic changes. Gavageadministration of 450 mg MEA/kg/day to pregnant rats resultedin maternal toxicity as evidenced by statistically significant( = 0.05) decreases in feed consumption on gestation days 6–8and 17–20 and on postpartum days 0–4. Additionally,statistically significant decreases in mean maternal body weightswere observed on gestation days 15, 17, and 20 and on lactationdays 0, 4, 7, and 21. Body weight gains of the 450 mg/kg/daydams were also significantly decreased (13% relative to controls)on gestation days 15–20. There was no evidence of maternaltoxicity at 40 or 120 mg/kg/day of MEA. Despite the maternaleffects observed at 450 mg/kg/day, no significant fetal effectswere observed at this or any dose level tested, nor were thereany indications of a treatment-related effect on postnatal growthor on the viability of offspring. Thus, it was concluded thatMEA was not developmentally toxic to Wistar rats following repeatedoral administration, even at maternally toxic dose levels ashigh as 450 mg/kg/day.     

Assessment of the no-observed-effect level (NOEL) of quinalphos in pregnant rats.

Technical quinalphos (0.5, 1.5, 2, 3 or 4.5 mg/kg body weight) was administered orally to pregnant rats from day 6-15 of gestation. At 3 and 4.5 mg/kg/day, quinalphos produced significant changes in hepatic ALT, ALP and serum ALT, AST, ALP and LDH activity along with hepatocellular changes in dams. The AchE activity in brain and red blood cells was also significantly inhibited at these two doses. At 0.5, 1.5 and 2 mg/kg/day, however, quinalphos did not produce any such changes. Up to a dose of 2 mg/kg/day there was no foetotoxic or teratogenic effect, as evidenced by number of implantation sites, percent resorption, foetal weight, morphological, visceral and skeletal evaluations. Hence, 2 mg/kg body weight of quinalphos could be considered as the no-observed-effect level (NOEL) on foetal and maternal toxicity in rats.     

Study of the teratogenic potential of FD & C Yellow No. 5 when given by gavage to rats

FD & C Yellow No. 5 (tartrazine) was given to Osborne-Mendel rats by gavage at dose levels of 0, 60, 100, 200, 400, 600 or 1000 mg/kg body weight/day on days 0–19 of gestation. No maternal or developmental toxicity was observed when the rats were killed on day 20. The mean daily food consumption for the entire period of gestation was significantly greater in the females given 1000 mg/kg body weight/day than in the controls, but maternal body-weight gain was not affected. No dose-related effects were observed in implantations, foetal viability or external foetal development. Foetal skeletal and visceral development was similar among foetuses from all groups. At the doses given, FD & C Yellow No. 5 was neither toxic nor teratogenic.     

The effect of lentinan on pregnancy of the New Zealand white rabbit

Lentinan at 0.1, 0.3 and 1.0 mg/kg/day was administered i.v. to the New Zealand White rabbit, once daily, on days 6–18 of gestation. There were no significant treatment-related effects on post implantation loss, mean litter size and weight, mean foetal weight or the incidence of minor skeletal or visceral anomalies.     

A teratogenic study of carbaryl in Swiss albino mice

To study the teratogenicity of carbaryl, groups of 10 pregnant mice were dosed, by gavage, with 0, 100, 150 or 200 mg carbaryl/kg body weight, in corn oil, on day 8 or day 12 of pregnancy or daily (as daily doses) from day 6 to day 15. The two higher doses were toxic to both dams and foetuses regardless of the timing of treatment. Treated dams generally showed reduced weight gains but total weight gain was significantly reduced only for dams given 200 mg carbaryl on day 8 or day 12 of gestation. Maternal mortality was increased in most groups given 150 or 200 mg carbaryl. Carbaryl treatment tended to reduce litter size, to increase the percentage of resorbed foetuses, and to reduce foetal weight. There were increased incidences of open eye, of certain visceral abnormalities, and of reduced ossification in virtually all treated groups. The variety of abnormalities in treated foetuses reflected the dysmorphogenic potential of the pesticide. More aberrations were seen in foetuses from dams treated throughout organogenesis than in those from dams given a single dose.     

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.     

Developmental toxicity of 2-butin-1,4-diol following oral administration to the rat

Developmental toxicity of 2-butin-1,4-diol was determined in groups of 18–22 pregnant Wistar rats at dose levels of 10, 40 and 80 mg/kg bw/day administered by gavage from days 6 to 15 pc. At 80 mg/kg bw/day food consumption and maternal body weight were reduced and one dam died during the treatment period. At this dose level the incidence of affected fetuses per litter with accessory 14th ribs was increased. This variation is assessed as an embryotoxic effect resulting from non-specific stress on the dams. No teratogenic effects were caused by 2-butin-1,4-diol. The NOAEL on the maternal and the developing organism was 40 mg/kg bw/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 orally administered thiabendazole in ICR mice.

Thiabendazole (TBZ) is a potent anthelmintic and fungicide used in the treatment of parasitic infections in humans and domestic animals and post-harvest protection of agricultural commodities. TBZ is not teratogenic or selectively foetotoxic in rats or rabbits, in contrast to several other benzimidazole derivatives. However, when administered orally to pregnant (Jcl:ICR) mice at lethal dosages, malformations were observed in treated fetuses. To assess whether the effects found in this previous study were attributable to maternal toxicity or TBZ the present study was conducted. TBZ doses of 25, 100 or 200 mg/kg/day were selected based on a preliminary range-finding study in which maternotoxicity was evident at doses of 200 mg/kg/day or above. The compound was administered during gestation days 6-15 as a solution in olive oil. Caesarean sections were completed on gestation day 18 and complete fetal examinations conducted. Decreases in maternal weight gain relative to controls were found at doses of 100 mg/kg/day or above, which paralleled decreases in foetal weights in these same dose groups. However, there were no treatment-related external, visceral or skeletal anomalies in any treatment group. Therefore, TBZ was not teratogenic or selectively foetotoxic in mice, with no-observed-effect levels (NOEL) of 25 and greater than 200 mg/kg/day for maternal and fetal weight effects and teratogenicity, respectively. These results indicate that foetal effects noted in previous studies in mice were probably secondary to severe maternal toxicity.     

Developmental toxicity of flupyrazofos, a new organophosphorus insecticide, in rats.

Flupyrazofos is a new type of pyrazole organophosporus insecticide, which has a high activity against the diamond-back moth (Plutella xylostella). The potential of this agent to induce developmental toxicity was investigated in the Sprague-Dawley rat. One hundred mated females (sperm in vaginal LAVAGE=day 0) were distributed among three treated groups and a control group. Flupyrazofos was administered by gavage to pregnant rats from days 7-17 of gestation at dose levels of 0, 5, 12 and 30 mg/kg/day. All dams were subjected to the caesarean section on day 20 of gestation and their fetuses were examined for external, visceral and skeletal abnormalities. At 30 mg/kg, maternal effects including mortality (4.3%), clinical signs of toxicity, decreased food intake, suppressed body weight, and increased weight of adrenal glands, kidney and heart were observed in dams. Litter values for corpora lutea, implantations, sex ratio and litter size were within the normal range. However, a reduction in the fetal weight and an increase in the incidence of fetal skeletal retardations were observed. At 12 mg/kg, toxic effects including mortality (4.2%), nasal discharge and some fetal skeletal retardation were observed. There were no signs of either maternal toxicity or embryotoxicity at 5 mg/kg. The results show that flupyrazofos induces fetal growth retardation only at maternally toxic doses in rats and the no-observed-adverse-effect levels (NOAELs) of this agent are considered to be 5 mg/kg for both dams and fetuses.     

Teratology study in fischer 344 rats exposed to ethylene oxide by inhalation

Pregnant Fischer 344 rats were exposed 6 hr/day to either 100, 33, or 10 ppm of ethylene oxide vapor on Days 6 through 15 of the gestation period. Two separate control groups were maintained under the same conditions but were exposed to room air only. Two other groups of rats were given a known rodent teratogen, aspirin, by gavage; one group was given 500 mg/kg body weight on Day 9 of gestation, and the other was given 625 mg/kg body weight on Day 10 of gestation. No treatment-related effects of ethylene oxide were noted for the following evaluations; maternal survival, litter size, number of implantation and resorption sites, and number of preimplantation losses. Exposure to 100 ppm of ethylene oxide resulted in a significant depression of body weight in the fetuses, but did not result in any abnormal effects of embryonic or fetal lethality, or teratologic effects of the soft tissues or skeleton. Consequently, ethylene oxide was not considered a teratogen by inhalation in the Fischer 344 rat at an exposure concentration of 100 ppm.     

A Study of Developmental Toxicity of Hydroquinone in the Rabbit

To obtain information on potential developmental toxicity, hydroquinone(HQ) was administered to pregnant New Zealand White rabbits(18 mated per dose group) in aqueous solution (0, 25, 75, or150 mg HQ/kg/day) by gavage on Gestation Days (GD) 6 to 18.Caesarean sections were performed on GD 30. Doses of 75 and150 mg/kg/day adversely affected feed consumption and/or bodyweights of dams during the treatment period. At these doses,however, treatment-related effects were not evident from physicalobservations, liver and kidney weights, premature delivery incidence,and caesarean sectioning data. The NOEL for maternal toxicitywas 25 mg/kg/day. In the 150 mg/ kg/day dose group, total incidencesof external, visceral, and skeletal findings for fetuses didnot differ statistically from controls. Slight, statisticallyinsignificant, increases were found, however, in the incidencesof ocular and minor skeletal malformations (microophthalmia,vertebral/rib defects, angulated hyoid arch) on both a per fetusand a per litter basis. Under the conditions of this study,HQ at 150 mg/kg/day produced minimal developmental alterationsin the presence of maternal toxicity. The NOEL for developmentaltoxicity was 75 mg/kg/day.     

Influence of Symmetrical Polychlorinated Biphenyl Isomers on Embryo and Fetal Development in Mice: II. Comparison of 4,4'-Dichlorobiphenyl, 3,3'4,4'-Tetrachlorobiphenyl, 3,3'5,5'-Tetrachlorobiphenyl, and 3,3'4,4'-Tetramethylbiphenyl

Outbred albino (CD-1) mice were given the following biphenylisomers by gavage in cottonseed oil on Days 6–15 of gestation:4,4'-dichlorobiphenyl (DCB) at 16, 32, and 64 mg/kg/day; 3,3',4,4'-tetrachlorobiphenyl(3,4-TCB) at 1, 2, 4, 8, 16, 32, and 64 mg/kg/day; 3,3',5,5'-tetrachlorobiphenyl(3,5-TCB) at 64 mg/ kg/day; and 3,3',4,4'-tetramethylbiphenyl(TMB) at 64 mg/kg/day. The mice were killed on Day 18 of gestation,necropsies were performed on the dams, and the fetuses wereexamined for external, visceral, and skeletal malformations.Although DCB was toxic to the dams at 64 mg/ kg/day, developmentaltoxicity was not detected. 3,4-TCB administration was followedby a significant (p < 0.01) increase in the average percentageof malformed fetuses per litter at 4 (7.2%), 8 (9.8%), 16 (25.4%),32 (50.0%), and 64 (75.0%) mg/kg/day versus the vehicle controlgroup (1.1%). None of the dosages tested was lethal to any ofthe dams. Significant decreases in maternal weight gain wereobserved at 16 mg/kg/day and above; however, the differencesfrom the control value most likely were due to significant decreasesin the mean number of live fetuses per dam, as the result ofreductions in the number of implants per dam, and significantincreases in the incidence of resorptions. Vaginal bleedingand other evidence of abortifacient effects also were presentin several dams in groups receiving 3,4-TCB at 16 mg/kg/dayand above. Cleft palate and hydronephrosis (significantly increasedat dosages of 4 mg/kg/day and above) were the predominant malformationsdetected. Thus, 3,4-TCB was found to be toxic to the conceptusat dosages of 4 mg/kg/day and above. Neither 3,5-TCB nor TMBshowed indications of maternal or developmental toxicity at64 mg/kg/day.     

Developmental toxicity study of chlorpyrifos in rats

Chlorpyrifos (O,O-diethyl-O-(3,5,6-trichloro-2-pyridyl)-phosphorothioate) was evaluated for potential developmental toxicity. Groups of 30 bred female Fischer 344 rats were given 0, 5, 15, and 25mg/kg per day by gavage on gestation days 6-15; the fetuses were evaluated on gestation day 21. Clinical signs of toxicity attributed to chlorpyrifos were noted in dams receiving 15 and 25mg/kg per day. Maternal effects in these groups also included depressed body weight and acetylcholinesterase activity. Fetal weight and viability were decreased, and fetal death and early resorption were increased at the 25mg/kg per day maternal dose. Visceral, skeletal, and external variations were also increased in this group. Chlorpyrifos showed fetotoxic and teratogenic effects at a maternal dose of 25mg/kg per day, a dose that also produced maternal toxicity.     

Teratogenicity studies on halogenated benzenes (pentachloro-, pentachloronitro- and hexabromo-) in rats.

The fungicide, pentachloronitrobenzene (PCNB), and fire retardants, pentachloro- (QCB) and hexabromobenzene (HBB) were administered orally to rats at 0, 50, 100 or 200 mg/kg on day 6-15 of gestation. The highest doses were associated with loss of maternal body weight gain but the loss was not statistically significant. At term, all dams were killed and foetuses removed to determine effects on prenatal survival and morphological development. All doses of QCB increased the foetal incidence of extra ribs in a dose-related manner while the 200 mg/kg dose also reduced the mean foetal weight and increased the incidence of sternal defects. PCNB and HBB had no effect at all doses.     

In Utero and Lactational Exposure to Fluoxetine in Wistar Rats: Pregnancy Outcomes and Sexual Development

This study evaluated the reproductive effects of fluoxetine exposure in utero and during lactation on pregnancy outcomes and the sexual development of offspring. Pregnant Wistar rats were treated daily with fluoxetine (0.4, 1.7 and 17 mg/kg/day) or distilled water by gavage from gestation day (GD) 7 to lactation day (LD) 21. A significant reduction in maternal body weight was observed during pregnancy and lactation in dams exposed to 17 mg/kg fluoxetine. Hormone analysis revealed an increase in progestagen and glucocorticoid metabolites on GD 15 and oestrogen and progestagen metabolites on LD 7 in dams treated with 17 mg/kg fluoxetine. Oestrogen metabolites also were increased on LD 7 in dams treated with 0.4 mg/kg fluoxetine. Besides that, an increase in the weight of the adrenal glands and a reduction in uterine weight in dams exposed to highest dose of fluoxetine were observed. Finally, pup birthweight and the viability and weaning indices also were reduced in animals exposed to 17 mg/kg fluoxetine. Overall, maternal hormonal changes were only observed at the highest dose tested, which also induced maternal and foetal toxicity. No significant changes were seen in dams or offspring exposed to therapeutic‐like doses.     

Developmental toxicity study of glycolic acid in rats.

The developmental toxicity of glycolic acid was assessed in rats by orally administering solutions of the test material in water over days 7-21 of gestation (the day of copulation plug detection was defined as day 1 of gestation). Groups of 25 mated female Crl: CD BR rats were gavaged at daily dose levels of 0, 75, 150, 300 or 600 mg/kg. The dams were euthanized on day 22 and the offspring were weighed, sexed, and examined for external, visceral, and skeletal alterations. Clear evidence of maternal toxicity was demonstrated at 600 mg/kg; adverse clinical observations were statistically significantly increased (wheezing/lung noise, abnormal gait/staggering, lethargy). In addition, maternal body weights, weight changes, and food consumption were statistically significantly reduced at this dose level. Marginal evidence of maternal toxicity was demonstrated at 300 mg/kg; wheezing/lung noise similar to that seen at 600 mg/kg was observed in 2 of 25 dams. This increase approached statistical significance (p = 0.0553). There was marked evidence of developmental toxicity at 600 mg/kg. Mean fetal weight was statistically significantly reduced while the incidences of skeletal (ribs, vertebra, and sternebra) malformations and variations were statistically significantly increased. At 300 mg/kg/day, there was a slight (2 affected fetuses from 2 litters) increase in the incidence of two skeletal malformations: fused ribs and fused vertebra. Although these increases were not statistically significant (p = 0.0555), they were consistent with findings seen at 600 mg/kg/day and thus were considered relevant. There was no other evidence of developmental toxicity at 300 mg/kg/day nor was any developmental toxicity seen at 150 or 75 mg/kg/day. Thus, the maternal and developmental no-observed-effect level (NOEL) was considered 150 mg/kg.     

The developmental toxicity of uranium in mice

To evaluate the developmental toxicity of uranium, 5 groups of 20 pregnant Swiss mice were given by gavage daily doses of 0, 5, 10, 25 and 50 mg/kg of uranyl acetate dihydrate on gestational days 6-15. Cesarean sections were performed on all females on gestation day 18. Fetuses were examined for external, visceral, and skeletal abnormalities. The results indicated that such exposure resulted in maternal toxicity as evidenced by reduced weight gain and food consumption during treatment, and increased relative liver weight. There were no treatment-related effects on the number of implantation sites per dam, or on the incidence of postimplantation loss (resorptions plus dead fetuses). The number of live fetuses per litter and the fetal sex ratio were not affected by the treatment. However, dose-related fetal toxicity, consisting primarily of reduced fetal body weight and body length, and an increased incidence of abnormalities was observed. Malformations (cleft palate, bipartite sternebrae) and developmental variations (reduced ossification and unossified skeletal variations) were noted at the 25 and 50 mg/kg per day test levels. Therefore, administration of uranyl acetate dihydrate during organogenesis in mice produced maternal toxicity at 5, 10, 25 and 50 mg/kg per day. The "no observable effect level" (NOEL) for fetotoxicity including teratogenicity was below 5 mg/kg per day, as some anomalies were observed at this dose. There was no evidence of embryolethality at any dosage level used in this study.