| ObjectivesPerfluorooctane sulfonate(PFOS)is a degradation product of sulfonyl-based fluorochemicals that are used extensively in industrial and household applications. Humans and wildlife are exposed to this class of compounds from several sources. Toxicity tests in experimental animals have raised concerns about immunity, reproductive,developmental,central neural effects and potential carcinogenicity of PFOS.However,the effect of PFOS on the developmental neurotoxicity has not been investigated thus far.Female rats and pups general toxicity was recorded in this study which was made in the way of PFOS exposure during prenatal or postnatal period.Glu concentrations,PKC activity and NMDAR1mRNA expression of cerebral cortex of developing rats were also tested.In this way,we take expects to know the effects on developing rats'central nervous system from PFOS and to approach developmental neurotoxicity mechanism of PFOS.Materials and Methods1.Dose preparationPotassium PFOS suspensions were prepared in deionized water with 2%Tween80 at concentrations according to experiment proposal.2%Tween80 or PFOS suspensions were added in rat feed flour and make the liquid and the flour mix thoroughly.Then there were three doses PFOS feed:0,1.6 and 3.2mg/kg.2.Animals and treatmentFemale rats were divided in to three groups randomly on gestation day I(GD1) and were dosed via oral gavage at dose levels of 0,1.6 and 3.2 mg PFOS/(kg feed)from GD1 to postnatal day 35(PND35).Appling cross-fosted way to make the litters be exposed to PFOS in prenatal or postnatal period to get three kinds litters:exposed in both prenatal and postnatal period(e.g.CC,LL and HH),only exposed in postnatal period(e.g.CL and CH)and only exposed in prenatal period(e.g.LC and HC).Litters took the same feed as foster females after ablactation.Pups within each dose group were sacrificed on PND1,7,14,21,28,35 and all females were sacrificed along with PND35 pups to get serum and brains.All samples were stored at -70℃.3.Methods(1)Recorded feed consumption of females and ECI was calculated.(2)Recorded body-weight changes of both females and pups through the experimental period.(3)Recorded the litters' number per dam and pup survival rate on PND1.(4)PFOS concentrations in serum from females and pups:High performance liquid chromatograghy/Mass spetrography(HPLC/MS).(5)Glu concentrations of cerebral cortex of pups:spectrophotometer.(6)PKC activity of cerebral cortex of pups:non-radioactive fluorescent test(7)NMDAR1mRNA expression:RT-PCR.4.Statistical analysisAll data were analyzed by SPSS 13.0 statistics soft.Continuous data sign to mean±SD and analyzed using One-Way ANOVA when the data were in normal distribution.LSD test was used when homogeneity of variances test was appropriate, and if not appropriate Dunnett's C test was used to the statistical significance of the individual groups.If the analysis of normal distribution was not appropriate,the Kruskal-Wsllis test was used to identify the statistical significance of the individual groups.Litters survival rates among three groups on PND1 were analyzed using Chi-square test.There were at least three samples for each test and p＜0.05 indicated significant difference.Results1.Body-weight,feed consumption or ECI of female ratsBody-weight gains of females in 1.6mg/(kg day)dose group were increased, while body-weight gains of 3.2mg/(kg day)dose group were reduced compared with control.No significant difference was observed in feed consumption or ECI.2.Litters survival rate on PND1Litters overall survival rate on PND1 in 3.2mg/(kg day)dose group was 94.1%,which significantly different from control(98.3%,p＜0.05,x~2=6.65)and 1.6mg/(kg day)dose group(99.1%,p＜0.01,x~2=11.64).3.Pups body-weight in developing periodPups body-weight in CC and LL group on PND1 were 6.52±0.15g and 5.96±0.15g,respectively and Significant difference was showed between CC and LL group.Body-weight gains of exposure groups increased soon through PND1-21 while were more slowly than control in the next period.Until PND35,values for body-weight were 111.66±4.91g,90.18±5.91g and 81.85±4.54g for C C,LL and HH,respectively.LL and HH body-weight values were reduced with statistical significance compared with CC(p＜0.05,F=21.49 and p＜0.01,F=29.81).4.PFOS concentrations in serum of female rats and developmental ratsWhen exposure period was over,PFOS concentrations in serum in 1.6 and 3.2mg/kg dose groups were significantly higher than control(p＜0.05,F=45.20).As for pups,PFOS concentrations in HH were significantly higher than control on PND1,too(p＜0.01,F=179.09).PFOS concentrations in serum of pups in CL,CH(only exposed to PFOS in postnatal days)were always significantly higher than CC through the whole developmental period(p＜0.01),while there was no significant difference between LC,HC(only exposed to PFOS in postnatal days)and CC.5.Glu concentrations of cerebral cortex of developmental ratsGlu concentrations in LC,HC and HH groups were significantly higher than CC on PND7(p＜0.05,F=4.578).When on PND14,values in LC were significantly higher than CC(p＜0.05,F=1.883).When on PND21,values in LL and He were significantly different from CC(p＜0.05,F=4.141).When on PND28,values in CL,CH and LL(all exposed in postnatal days)were significantly lower than CC(CL and CH,p＜0.05; LL,p＜0.01;F=2.908).6.PKC activity of cerebral cortex of developmental ratsPups PKC activity in HH were significantly higher than CC on PND1(p＜0.01, F=11.734).The values in CH and HH were significantly higher than CC on PND7(CH, p＜0.05;HH,p＜0.01;F=2.761).When on PND21,values in LL were significantly higher than CC(p＜0.05,F=3.339).When on PND35,values in CH were significantly lower than CC(p＜0.05,F=1.870).7.NMDAR1mRNA expression of cerebral cortex of developmental ratsPups NMDAR1mRNA expression of CH were significantly lower than CC on PND7(p＜0.05,F=4.240).The values in LL,HC and HH were significantly lower than CC on PND14(HC,p＜0.05;LL,HH,p＜0.01;F=14.047).When on PND21,values in LC and HH were significantly higher than CC(p＜0.05,F=3.114).When on PND28,values in CH and HH were significantly lower than CC(p＜0.01,F=9.692).When on PND35,values in HC were significantly higher than CC(p＜0.05,F=1.940). Conclusions1.The effect of PFOS on body-weight of both females and pups in this study was stimulating firstly but then inhibited.2.Results of this study indicated that in utero exposure to PFOS causally contributed to pup mortality of postnatal day1-7.3.High PFOS concentrations were tested in PND1 pups serum,which indicated PFOS can permeate placental barrier translating PFOS from females to pups.4.In utero exposure to PFOS can resulted in PKC activity of pups significantly increased on PND1.The effect of exposure in postnatal days on PKC activity was stimulating firstly and then inhibited.Glu concentrations change tendency is similar with PKC activity here.The results here indicates that PFOS has hormesis.5.Exposed to PFOS in prenatal period can delay the appearance time of NMDAR1mRNA expression physiological peak.It also can intensify the fluctuation of NMDAR1mRNA expression.6.In this study,developmental rats occurred neurotoxicity at the same serum PFOS concentrations with non-occupational exposure population.
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