Developmental triclosan exposure decreases maternal, fetal, and early neonatal thyroxine: a dynamic and kinetic evaluation of a putative mode-of-action

This work tests the mode-of-action (MOA) hypothesis that maternal and developmental triclosan (TCS) exposure decreases circulating thyroxine (T4) concentrations via up-regulation of hepatic catabolism and elimination of T4. Time-pregnant Long-Evans rats received TCS po (0-300mg/kg/day) from gestational day (GD) 6 through postnatal day (PND) 21. Serum and liver were collected from dams (GD20, PND22) and offspring (GD20, PND4, PND14, PND21). Serum T4, triiodothyronine (T3), and thyroid-stimulating hormone (TSH) concentrations were measured by radioimmunoassay. Ethoxy-O-deethylase (EROD), pentoxyresorufin-O-depentylase (PROD) and uridine diphosphate glucuronyltransferase (UGT) enzyme activities were measured in liver microsomes. Custom Taqman(?) qPCR arrays were employed to measure hepatic mRNA expression of select cytochrome P450s, UGTs, sulfotransferases, transporters, and thyroid hormone-responsive genes. TCS was quantified by LC/MS/MS in serum and liver. Serum T4 decreased approximately 30% in GD20 dams and fetuses, PND4 pups and PND22 dams (300mg/kg/day). Hepatic PROD activity increased 2-3 fold in PND4 pups and PND22 dams, and UGT activity was 1.5 fold higher in PND22 dams only (300mg/kg/day). Minor up-regulation of Cyp2b and Cyp3a expression in dams was consistent with hypothesized activation of the constitutive androstane and/or pregnane X receptor. T4 reductions of 30% for dams and GD20 and PND4 offspring with concomitant increases in PROD (PND4 neonates and PND22 dams) and UGT activity (PND22 dams) suggest that up-regulated hepatic catabolism may contribute to TCS-induced hypothyroxinemia during development. Serum and liver TCS concentrations demonstrated greater fetal than postnatal internal exposure, consistent with the lack of T4 changes in PND14 and PND21 offspring. These data support the MOA hypothesis that TCS exposure leads to hypothyroxinemia via increased hepatic catabolism; however, the minor effects on thyroid hormone metabolism may reflect the low efficacy of TCS as thyroid hormone disruptor or highlight the possibility that other MOAs may also contribute to the observed maternal and early neonatal hypothyroxinemia.     

Towards a Pragmatic Alternative Testing Strategy for the Detection of Reproductive Toxicants

Exposure of rodents in utero to perfluorooctane sulfonate (PFOS) impairs perinatal development and survival. Following intravenous or gavage exposure of C57Bl/6 mouse dams on gestational day (GD) 16 to ³⁵S-PFOS (12.5 mg/kg), we determined the distribution in dams, fetuses (GD18 and GD20) and pups (postnatal day 1, PND1) employing whole-body autoradiography and liquid scintillation counting. In dams, levels were highest in liver and lungs. After placental transfer, ³⁵S-PFOS was present on GD18 at 2–3 times higher levels in lungs, liver and kidneys than in maternal blood. In PND1 pups, levels in lungs were significantly higher than in GD18 fetuses. A heterogeneous distribution of ³⁵S-PFOS was observed in brains of fetuses and pups, with levels higher than in maternal brain. This first demonstration of substantial localization of PFOS to both perinatal and adult lungs is consistent with evidence describing the lung as a target for the toxicity of PFOS at these ages.     

Developmental toxicity of perfluorooctane sulfonate (PFOS) is not dependent on expression of peroxisome proliferator activated receptor-alpha (PPAR alpha) in the mouse

Perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) are members of a family of perfluorinated compounds. Both are environmentally persistent and found in the serum of wildlife and humans. PFOS and PFOA are developmentally toxic in laboratory rodents. Exposure to these chemicals in utero delays development and reduces postnatal survival and growth. Exposure to PFOS on the last 4 days of gestation in the rat is sufficient to reduce neonatal survival. PFOS and PFOA are weak agonists of peroxisome proliferator activated receptor-alpha (PPAR alpha). The reduced postnatal survival of neonatal mice exposed to PFOA was recently shown to depend on expression of PPAR alpha. This study used PPAR alpha knockout (KO) and 129S1/SvlmJ wild type (WT) mice to determine if PPAR alpha expression is required for the developmental toxicity of PFOS. After mating overnight, the next day was designated gestation day (GD) 0. WT females were weighed and dosed orally from GD15 to 18 with 0.5% Tween-20, 4.5, 6.5, 8.5, or 10.5mg PFOS/kg/day. KO females were dosed with 0.5% Tween-20, 8.5 or 10.5mg PFOS/kg/day. Dams and pups were observed daily and pups were weighed on postnatal day (PND) 1 and PND15. Eye opening was recorded from PND12 to 15. Dams and pups were killed on PND15, body and liver weights recorded, and serum collected. PFOS did not affect maternal weight gain or body or liver weights of the dams on PND15. Neonatal survival (PND1-15) was significantly reduced by PFOS in both WT and KO litters at all doses. WT and KO pup birth weight and weight gain from PND1 to 15 were not significantly affected by PFOS exposure. Relative liver weight of WT and KO pups was significantly increased by the 10.5mg/kg dose. Eye opening of PFOS-exposed pups was slightly delayed in WT and KO on PND13 or 14, respectively. Because results in WT and KO were comparable, it is concluded that PFOS-induced neonatal lethality and delayed eye opening are not dependent on activation of PPAR alpha.     

Developmental toxicity of perfluorooctane sulfonate (PFOS) is not dependent on expression of peroxisome proliferator activated receptor-alpha (PPARα) in the mouse

Perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) are members of a family of perfluorinated compounds. Both are environmentally persistent and found in the serum of wildlife and humans. PFOS and PFOA are developmentally toxic in laboratory rodents. Exposure to these chemicals in utero delays development and reduces postnatal survival and growth. Exposure to PFOS on the last 4 days of gestation in the rat is sufficient to reduce neonatal survival. PFOS and PFOA are weak agonists of peroxisome proliferator activated receptor-alpha (PPARα). The reduced postnatal survival of neonatal mice exposed to PFOA was recently shown to depend on expression of PPARα. This study used PPARα knockout (KO) and 129S1/SvlmJ wild type (WT) mice to determine if PPARα expression is required for the developmental toxicity of PFOS. After mating overnight, the next day was designated gestation day (GD) 0. WT females were weighed and dosed orally from GD15 to 18 with 0.5% Tween-20, 4.5, 6.5, 8.5, or 10.5 mg PFOS/kg/day. KO females were dosed with 0.5% Tween-20, 8.5 or 10.5 mg PFOS/kg/day. Dams and pups were observed daily and pups were weighed on postnatal day (PND) 1 and PND15. Eye opening was recorded from PND12 to 15. Dams and pups were killed on PND15, body and liver weights recorded, and serum collected. PFOS did not affect maternal weight gain or body or liver weights of the dams on PND15. Neonatal survival (PND1–15) was significantly reduced by PFOS in both WT and KO litters at all doses. WT and KO pup birth weight and weight gain from PND1 to 15 were not significantly affected by PFOS exposure. Relative liver weight of WT and KO pups was significantly increased by the 10.5 mg/kg dose. Eye opening of PFOS-exposed pups was slightly delayed in WT and KO on PND13 or 14, respectively. Because results in WT and KO were comparable, it is concluded that PFOS-induced neonatal lethality and delayed eye opening are not dependent on activation of PPARα.     

Evaluation of potential reproductive and developmental toxicity of potassium perfluorohexanesulfonate in Sprague Dawley rats

This study evaluates the potential reproductive and developmental toxicity of perfluorohexanesulfonate (PFHxS), a surfactant found in sera of the general population. In a modified OECD 422 guideline-based design, 15 rats per sex and treatment group (control, 0.3, 1, 3, and 10 mg/kg-d) were dosed by gavage with potassium PFHxS (K⁺PFHxS) or vehicle (0.5% carboxymethylcellulose) 14 days prior to cohabitation, during cohabitation, and until the day before sacrifice (21 days of lactation or presumed gestation day 25 (if not pregnant) for females and minimum of 42 days of treatment for males). Offspring were not dosed by gavage but were exposed by placental transfer in utero and potentially exposed via milk. Evaluations were made for reproductive success, clinical signs, body weight, food consumption, estrous cycling, neurobehavioral effects, gross and microscopic anatomy of selected organs, sperm, hematology, clinical pathology, and concentration of PFHxS in serum and liver. Additional three rats per sex per group were added to obtain sera and liver samples for PFHxS concentration determinations during the study. No reproductive or developmental effects were observed. There were no treatment-related effects in dams or offspring. K⁺PFHxS-induced effects noted in parental males included: (1) at all doses, reductions in serum total cholesterol; (2) at 0.3, 3, and 10 mg/kg-d, decreased prothrombin time; (3) at 3 and 10 mg/kg-d, increased liver-to-body weight and liver-to-brain weight ratios, centrilobular hepatocellular hypertrophy, hyperplasia of thyroid follicular cells, and decreased hematocrit; (4) at 10 mg/kg-d, decreased triglycerides and increased albumin, BUN, ALP, Ca²⁺, and A/G ratio. Serum and liver concentrations of PFHxS are reported for parents, fetuses, and pups. PFHxS was not a reproductive or developmental toxicant under study conditions.     

Exposure to perfluorooctane sulfonate during pregnancy in rat and mouse. II: postnatal evaluation.

The postnatal effects of in utero exposure to perfluorooctane sulfonate (PFOS, C8F17SO3-) were evaluated in the rat and mouse. Pregnant Sprague-Dawley rats were given 1, 2, 3, 5, or 10 mg/kg PFOS daily by gavage from gestation day (GD) 2 to GD 21; pregnant CD-1 mice were treated with 1, 5, 10, 15, and 20 mg/kg PFOS from GD 1 to GD 18. Controls received 0.5% Tween-20 vehicle (1 ml/kg for rats and 10 ml/kg for mice). At parturition, newborns were observed for clinical signs and survival. All animals were born alive and initially appeared to be active. In the highest dosage groups (10 mg/kg for rat and 20 mg/kg for mouse), the neonates became pale, inactive, and moribund within 30-60 min, and all died soon afterward. In the 5 mg/kg (rat) and 15 mg/kg (mouse) dosage groups, the neonates also became moribund but survived for a longer period of time (8-12 h). Over 95% of these animals died within 24 h. Approximately 50% of offspring died at 3 mg/kg for rat and 10 mg/kg for mouse. Cross-fostering the PFOS-exposed rat neonates (5 mg/kg) to control nursing dams failed to improve survival. Serum concentrations of PFOS in newborn rats mirrored the maternal administered dosage and were similar to those in the maternal circulation at GD 21; PFOS levels in the surviving neonates declined in the ensuing days. Small but significant and persistent growth lags were detected in surviving rat and mouse pups exposed to PFOS prenatally, and slight delays in eye opening were noted. Significant increases in liver weight were observed in the PFOS-exposed mouse pups. Serum thyroxine levels were suppressed in the PFOS-treated rat pups, although triiodothyronine and thyroid-stimulating hormone [TSH] levels were not altered. Choline acetyltransferase activity (an enzyme that is sensitive to thyroid status) in the prefrontal cortex of rat pups exposed to PFOS prenatally was slightly reduced, but activity in the hippocampus was not affected. Development of learning, determined by T-maze delayed alternation in weanling rats, was not affected by PFOS exposure. These results indicate that in utero exposure to PFOS severely compromised postnatal survival of neonatal rats and mice, and caused delays in growth and development that were accompanied by hypothyroxinemia in the surviving rat pups.     

Developmental exposure to brominated diphenyl ethers results in thyroid hormone disruption.

The objective of the current study was to characterize the effects of DE-71 (a commercial polybrominated diphenyl ether mixture containing mostly tetra- and penta-bromodiphenyl ethers) on thyroid hormones and hepatic enzyme activity in offspring, following perinatal maternal exposure. Primiparous Long-Evans rats were orally administered DE-71 (0, 1, 10, and 30 mg/kg/day) in corn oil from gestation day (GD) 6 to postnatal day (PND) 21. Serum and liver samples obtained from dams (GD 20 and PND 22), fetuses (GD 20), and offspring (PNDs 4, 14, 36, and 90) were analyzed for circulating total serum thyroxine (T(4)) and triiodothyronine (T(3)), or hepatic microsomal ethoxy- and pentoxy-resorufin-O-deethylase (EROD and PROD), and uridine diphosphoglucuronosyl transferase (UDPGT) activity. There were no significant effects of treatment on maternal body weight gain, litter size, or sex ratio, nor were there any effects on any measures of offspring viability or growth. Serum T(4) was reduced in a dose-dependent manner in fetuses on GD 20 (at least 15%) and offspring on PND 4 and PND 14 (50 and 64% maximal in the 10 and 30 mg/kg/day groups, respectively), but recovered to control levels by PND 36. Reduction in serum T(4) was also noted in GD 20 dams (48% at highest dose), as well as PND 22 dams (44% at highest dose). There was no significant effect of DE 71 on T(3) concentrations at any time in the dams or the offspring. Increased liver to body weight ratios in offspring were consistent with induction of EROD (maximal 95-fold), PROD (maximal 26-fold) or UDPGT (maximal 4.7-fold). Induction of PROD was similar in both dams and offspring; however, EROD and UDPGT induction were much greater in offspring compared to dams (EROD = 3.8-fold; UDPGT = 0.5-fold). These data support the conclusion that DE-71 is an endocrine disrupter in rats during development.     

Effect of in utero and lactational exposure of triazophos on reproductive system functions in male offsprings,Rattus norvegicus

In the present study, Triazophos (TZ) was used at acceptable daily intake (ADI) to investigate the consequence of prenatal and postnatal exposure on reproductive functions in the male offsprings. Pregnant females were divided into three groups, the first group was orally gavaged with olive oil (control), the second group was administered with 0.01?mg kg^?1 bw of the ADI of TZ from gestation day (GD) 1 until parturition (designated as P group) and the third group was gavaged with the same dose from GD1 to postnatal day (PND) 21 of lactation (marked as P?+?L group). Non-significant reduction occurred in the body weight of pups except at (PND) 35 during which body weight of P?+?L group pups significantly decreased. Male offsprings born to TZ exposed females showed significant changes at maturity (PND 63) in weight of liver, thyroid and testis, alterations in the levels of protein, urea, creatinine in plasma and abnormal levels of cholesterol, phospholipids and lipid peroxidation in testicular homogenate. Gonadal inhibition in TZ exposed progeny was reflected from a significant fall in sperm count, sperm motility, plasma testosterone level and histopathological alterations in testis. Hence, in utero and lactational exposure to ADI level of TZ influences testis development and functions in the male offsprings. Further investigations are suggested with germline studies of offsprings to examine the transgenerational effect of TZ exposure.     

Perfluorooctanoic acid and perfluorononanoic acid in fetal and neonatal mice following in utero exposure to 8-2 fluorotelomer alcohol.

8-2 Fluorotelomer alcohol (FTOH) and its metabolites, perfluorooctanoic acid (PFOA) and perfluorononanoic acid (PFNA), are developmental toxicants but metabolism and distribution during pregnancy are not known. To examine this, timed-pregnant mice received a single gavage dose (30 mg 8-2 FTOH/kg body weight) on gestational day (GD) 8. Maternal and neonatal serum and liver as well as fetal and neonatal homogenate extracts were analyzed using gas chromatography coupled with mass spectrometry. During gestation (GD9 to GD18), maternal serum and liver concentrations of PFOA decreased from 789 +/- 41 to 668 +/- 23 ng/ml and from 673 +/- 23 to 587 +/- 55 ng/g, respectively. PFOA was transferred to the developing fetuses as early as 24-h posttreatment with concentrations increasing from 45 +/- 9 ng/g (GD10) to 140 +/- 32 ng/g (GD18), while PFNA was quantifiable only at GD18 (31 +/- 4 ng/g). Post-partum, maternal serum PFOA concentrations decreased from 451 +/- 21 ng/ml postnatal day (PND) 1 to 52 +/- 19 ng/ml (PND15) and PFNA concentrations, although fivefold less, exhibited a similar trend. Immediately after birth, pups were cross-fostered with dams that had been treated during gestation with 8-2 FTOH (T) or vehicle (C) resulting in four treatment groups in which the first letter represents in utero (fetal) exposure and the second represents lactational (neonatal) exposure: C/C, T/C, C/T, T/T. On PND1, neonatal whole-body homogenate concentrations of PFOA from T/T and T/C groups averaged 200 +/- 26 ng/g, decreased to 149 +/- 19 ng/g at PND3 and this decreasing trend was seen in both neonatal liver and serum from PND3 to PND15. Based on detectible amounts of PFOA in neonatal serum in the C/T group on PND3 (57 +/- 11 ng/ml) and on PND15 (58 +/- 3 ng/ml), we suggest that the neonates were exposed through lactation. In conclusion, exposure of neonates to PFOA and PFNA occurs both pre- and postnatally following maternal 8-2 FTOH exposure on GD8.     

PCBs, thyroid hormones, and ototoxicity in rats: cross-fostering experiments demonstrate the impact of postnatal lactation exposure.

Previous research has demonstrated the sensitivity of the developing rat to the hypothyroxinemic and ototoxic effects of perinatal exposure to Aroclor 1254 (A1254). We tested the hypothesis that postnatal exposure via lactation is the major cause of the ototoxicity by cross fostering animals at birth. Primiparous rats (22-24/dose) received 0 or 6 mg/kg A1254 (po in corn oil) from gestation day (GD) 6 to postnatal day (PND) 21. On the day of birth, half of the treated litters and half of the control litters were cross-fostered, resulting in the following groups: Ctrl/Ctrl (controls); A1254/A1254 (perinatal exposure); A1254/Ctrl (prenatal exposure only); and Ctrl/A1254 (postnatal exposure only). We assessed offspring at a number of ages for: serum thyroid hormone concentrations, liver and brain concentrations of PCBs, body weight, mortality, age of eye opening, auditory startle amplitudes, and auditory thresholds for 1 kHz and 40 kHz tones. Circulating thyroxine (T(4)) concentrations were sharply reduced at GD 21 in the A1254-exposed group, and on PND 3, 7, 14, and 21 in the A1254/A1254 and the Ctrl/A1254 groups. Smaller decreases in T(4) were observed in the A1254/Ctrl group on PND 3, 7, and 14. PCB concentrations in the liver on PND 21 were sharply elevated in the A1254/A1254 and Ctrl/A1254 groups. Much smaller increases were seen in the A1254/Ctrl group. Age of eye-opening and startle amplitudes were unaffected by treatment. A1254 exposure caused permanent hearing deficits (20 dB increase) at the low frequency (1 kHz) in the A1254/A1254 and Ctrl/A1254 groups. The present findings demonstrated that the critical period for the ototoxicity of developmental A1254 exposure is within the first few postnatal weeks in the rat. This effect is consistent with the greater degree of postnatal hypothyroxinemia resulting from the greater magnitude of exposure that occurs postnatally via lactation.     

Thyroxine Replacement Attenuates Hypothyroxinemia, Hearing Loss, and Motor Deficits Following Developmental Exposure to Aroclor 1254 in Rats

The nervous system is dependent upon thyroid hormones for normaldevelopment, and we previously reported that developmental Aroclor1254 (A1254) exposure caused hypothyroxinemia, hearing lossand other behavioral changes in rats. (Goldey et al, 1995a;Herr et al, 1996). The hypothesis that A1254-induced hypothyroxinemiamay have contributed to the observed functional changes wastested in primiparous Long-Evans rats given daily oral dosesof corn oil (control) or 8 mg/kg of Aroclor 1254 from gestationday (GD) 6 through postnatal day (PND) 21. In addition, fromPND 4 to PND 21, all pups in one-half of the litters receiveddaily, subcutaneous injections of saline or 100 µg/kgthyroxine (T4), to yield four groups of litters: corn oil phissaline (CO-S), corn oil plus T4 (CO-T4), Aroclor 1254 plus saline(PCB-S), and Aroclor 1254 plus T4 (PCB-T4). We measured thyroidhormone concentrations (T4 and T3) in serum collected from 7-,14-, and 21-day-old pups. The kinetics of the injected T4 werealso monitored in the CO-T4 and PCB-T4 groups on PND 7 and 21by measuring T4 and T3 at 1, 3, 5, 8, and 24 h after injection.Circulating T4 concentrations were dramatically depleted inthe PCB-S group relative to CO-S. The kinetics study indicatedthat T4 therapy raised circulating T4 concentrations followingin the PCB-T4 pups to near CO-S concentrations, but only forapproximately 6 h postinjection, and T4 concentrations fellprecipitously thereafter to near PCB-S concentrations. In accordwith previous studies, PCB-S pups showed early eye opening,an effect which was exacerbated by T4 injection (in both theCO-T4 and the PCB-T4 groups). Motor activity (figure-eight maze)testing also replicated our finding of an age-dependent, transientreduction in motor activity on PND 15 that was significantlyattenuated in the PCB-T4 group. Similarly, we again found reducedacoustic startle amplitudes on PND 23 and low-frequency (1 kHz)hearing loss in animals tested as adults (the latter derterminedby reflex modification audiometry Importantly, the hearing lossat 1kHz in PCB-exposed animals was significantly attenuatedby T4 replacement therapy. These data suggest the hypothesisthat hypothyroxinemia is involved in PCB-induced alterationsin motor and auditory function, while other effects (e.g., eyeopening) appear to have a different mechanism of action.     

Ninety-day toxicity and one-generation reproduction study in rats exposed to allethrin-based liquid mosquito repellent

Rats exposed to liquid mosquito repellent (LMR) containing allethrin (3.6% w/w) 8-hrs/ day for a period of ninety days did not produce any signs of toxicity or death. Significant increases in relative weight of liver and adrenal in males, brain and thyroid in females were observed. No significant changes were noticed in clinical enzyme profile, gonadal enzymes and histopathology of vital organs except mild changes in the activities of liver and serum alkaline phosphates (ALP), testicular glucose-6-phosphate dehydrogenase (G-6PDH) and epididymal sorbitol dehydrogenase (SDH). Rats exposed to LMR for one generation had not produced changes in their reproductive indices such as fertility index, gestation index, live pups/ dam and sex ratio. There was no change in the preweanling evaluation of pups such as survival and growth index on post-natal days (PND) 0, 4, 7,14 and 21. No significant pathomorphological changes were observed in liver, brain, kidney and gonads of PND 21 pups. Absences of any major adverse effects in the adult as well as weanling rats suggest the safe use of allethrin-based LMR.     

Prenatal PFOS exposure induces oxidative stress and apoptosis in the lung of rat off-spring

Perfluorooctane sulfonate (PFOS) could induce neonatal pulmonary injuries in rodents. The aim of this study was to investigate the underlying mode of action. Pregnant rats were dosed orally with PFOS (0, 0.1 and 2.0mg/kgd) from gestation days (GD) 1 to 21. Lung samples from postnatal day (PND) 0 and 21 pups were analyzed for the toxic effects of PFOS. The results showed that maternal exposure to 2.0mg/kgd PFOS caused severe histopathological changes along with marked oxidative injuries and cell apoptosis in offspring lungs; at the same time, the ratio of Bax to Bcl-2, release of cytochrome c (Cyt c) from mitochondria to cytoplasm, expressions of Fas and Fas-L, and activities of caspase-3, -8 and -9 were up-regulated correspondingly. The results indicate that oxidative stress and both intrinsic and extrinsic cell death pathways were involved in prenatal PFOS exposure-induced injuries in postnatal lungs.     

Tissue manganese concentrations in lactating rats and their offspring following combined in utero and lactation exposure to inhaled manganese sulfate.

There is little information regarding the tissue distribution of manganese in neonates following inhalation. This study determined tissue manganese concentrations in lactating CD rats and their offspring following manganese sulfate (MnSO4) aerosol inhalation. Except for the period of parturition, dams and their offspring were exposed to air or MnSO4 (0.05, 0.5, or 1 mg Mn/m3) for 6 h/day, 7 days/week starting 28 days prior to breeding through postnatal day (PND) 18. Despite increased manganese concentrations in several maternal tissues, MnSO4 inhalation exposure did not affect body weight gain, terminal (PND 18) body weight, or organ weights in the dams. Exposure to MnSO4 at 1 mg Mn/m3 resulted in decreased pup body weights on PND 19 and decreased brain weights in some PND 14 to PND 45 pups. Exposure to MnSO4 at > or =0.05 mg Mn/m3 was associated with increased stomach content, blood, liver, and skull cap manganese concentrations in PND 1 pups, increased brain, lung, and femur manganese concentrations in PND 14 pups, and elevated olfactory bulb, cerebellum, and striatum manganese concentrations in PND 19 pups. When compared to controls, MnSO4 exposure to > or =0.5 mg Mn/m3 increased liver and blood manganese concentrations in PND 14 pups and increased liver, pancreas, and femur manganese concentrations in PND 19 pups. Manganese concentrations returned to control values in all offspring tissues by PND 45 +/- 1. Our data demonstrate that neonatal tissue manganese concentrations observed following MnSO4 inhalation are dependent on the MnSO4 exposure concentration and the age of the animal.     

Exposure to perfluorooctane sulfonate during pregnancy in rat and mouse. I: maternal and prenatal evaluations.

The maternal and developmental toxicities of perfluorooctane sulfonate (PFOS, C8F17SO3-) were evaluated in the rat and mouse. PFOS is an environmentally persistent compound used as a surfactant and occurs as a degradation product of both perfluorooctane sulfonyl fluoride and substituted perfluorooctane sulfonamido components found in many commercial and consumer applications. Pregnant Sprague-Dawley rats were given 1, 2, 3, 5, or 10 mg/kg PFOS daily by gavage from gestational day (GD) 2 to GD 20; CD-1 mice were similarly treated with 1, 5, 10, 15, and 20 mg/kg PFOS from GD 1 to GD 17. Controls received 0.5% Tween-20 vehicle (1 ml/kg for rats and 10 ml/kg for mice). Maternal weight gain, food and water consumption, and serum chemistry were monitored. Rats were euthanized on GD 21 and mice on GD 18. PFOS levels in maternal serum and in maternal and fetal livers were determined. Maternal weight gains in both species were suppressed by PFOS in a dose-dependent manner, likely attributed to reduced food and water intake. Serum PFOS levels increased with dosage, and liver levels were approximately fourfold higher than serum. Serum thyroxine (T4) and triiodothyronine (T3) in the PFOS-treated rat dams were significantly reduced as early as one week after chemical exposure, although no feedback response of thyroid-stimulating hormone (TSH) was observed. A similar pattern of reduction in T4 was also seen in the pregnant mice. Maternal serum triglycerides were significantly reduced, particularly in the high-dose groups, although cholesterol levels were not affected. In the mouse dams, PFOS produced a marked enlargement of the liver at 10 mg/kg and higher dosages. In the rat fetuses, PFOS was detected in the liver but at levels nearly half of those in the maternal counterparts, regardless of administered doses. In both rodent species, PFOS did not alter the numbers of implantations or live fetuses at term, although small deficits in fetal weight were noted in the rat. A host of birth defects, including cleft palate, anasarca, ventricular septal defect, and enlargement of the right atrium, were seen in both rats and mice, primarily in the 10 and 20 mg/kg dosage groups, respectively. Our results demonstrate both maternal and developmental toxicity of PFOS in the rat and mouse.     

Disruption of thyroid hormone homeostasis at weaning of Holtzman rats by lactational but not in utero exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin.

The purpose of this study is to clarify whether lactational exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is entirely responsible for the perturbation in thyroid hormone homeostasis during the neonatal period. Pregnant Holtzman rats were given a single oral dose of 1.0 mug TCDD/kg body weight on gestational day 15. Half of the litters were cross-fostered with the half of the dams treated with vehicle on postnatal day (PND) 1 to make four groups of rats, control (C/C), prenatal TCDD exposure only (T/C), postnatal TCDD exposure only (C/T), and both prenatal and postnatal TCDD exposure (T/T). On PND 21, the C/T and T/T groups, but not the T/C and C/C groups, showed a significant decrease in serum total thyroxin (TT4) and free thyroxin (FT4) concentrations in both sexes and a significant increase in serum thyroid-stimulating hormone (TSH) levels, particularly male pups. These two groups of male and female pups had significantly higher concentrations of TCDD in the liver, with marked induction of cytochrome P450 (CYP) 1A1 mRNA and intense immunostaining of CYP1A1 in the liver. UDP glycosyltransferase 1 family, polypeptide A6 (UGT1A6) and UGT1A7 mRNAs were induced in their livers, with marked immunostaining of UGT1A6. The transfer of TCDD from dams to the pups was confirmed by the detection of TCDD in mother's milk remaining in the stomachs of lactationally exposed pups on PND 1. The present results demonstrate that lactational, but not in utero, exposure to TCDD was responsible for the disruption of thyroid hormone homeostasis.     

Neonatal mortality from in utero exposure to perfluorooctanesulfonate (PFOS) in Sprague-Dawley rats: dose-response, and biochemical and pharamacokinetic parameters

Perfluorooctanesulfonate (PFOS) is a widely distributed, environmentally persistent acid found at low levels in human, wildlife, and environmental media samples. Neonatal mortality has been observed following PFOS exposure in a two-generation reproduction study in rats and after dosing pregnant rats and mice during gestation. Objectives of the current study were to better define the dose-response curve for neonatal mortality in rat pups born to PFOS-exposed dams and to investigate biochemical and pharmacokinetic parameters potentially related to the etiology of effects observed in neonatal rat pups. In the current study, additional doses of 0.8, 1.0, 1.2, and 2.0 mg/kg/day were included with original doses used in the two-generation study of 0.4 and 1.6 mg/kg/day in order to obtain data in the critical range of the dose-response curve. Biochemical parameters investigated in dams and litters included: (1) serum lipids, glucose, mevalonic acid, and thyroid hormones; (2) milk cholesterol; and (3) liver lipids. Pharmacokinetic parameters investigated included the interrelationship of administered oral dose of PFOS to maternal body burden of PFOS and the transfer of maternal body burden to the fetus in utero and pup during lactation, as these factors may affect neonatal toxicity. Dosing of dams occurred for 6 weeks prior to mating with untreated breeder males, through confirmed mating, gestation, and day four of lactation. Dose levels for the dose-response and etiological investigation were 0.0, 0.4, 0.8, 1.0, 1.2, 1.6, and 2.0 mg/kg/day PFOS. Statistically significant decreases in gestation length were observed in the 0.8 mg/kg and higher dose groups. Decreases in viability through lactation day 5 were observed in the 0.8 mg/kg and higher dose groups, becoming statistically significant in the 1.6 and 2.0 mg/kg dose groups. Reduced neonatal survival did not appear to be the result of reductions in lipids, glucose utilization, or thyroid hormones. The endpoints of gestation length and decreased viability were positively correlated, suggesting that late-stage fetal development may be affected in pups exposed to PFOS in utero and may contribute to the observed mortality. Benchmark dose (BMD) estimates for decreased gestation length, birth weight, pup weight on lactation day 5, pup weight gain through lactation day 5, and viability resulted in values ranging from 0.27 to 0.89mg/kg/day for the lower 95% confidence limit of the BMD5 (BMDL5). Results of analyses for PFOS in biological matrices indicate a linear proportionality of mean serum PFOS concentration to maternal administered dose prior to mating and through the first two trimesters of gestation. However, at 21 days of gestation, mean serum PFOS concentrations were notably reduced from values measured earlier in gestation. Urinary and fecal elimination was low as expected from prior observations in adult rats. Significant transfer of PFOS from dam to fetus in utero was confirmed, and results suggest that dam and corresponding fetal body burdens, as indicated by serum and liver PFOS levels, correlate with neonatal survival.