Effects Of Lead Exposure On Rat Placental Apoptosis,Smad4and S100B Protein Expression During Different Periods Of Pregnancy

Objective To investigate the correlation between apoptosis, Smad4, S100B protein and the level of blood lead of placenta during different periods of pregnancy.Methods All108wistar rats were divided into four groups randomly. All rats were orally fed with0.025%lead acetate during different periods of pregnancy. Blood lead levels were determined by atomic absorption spectrophotometry at the end of pregnancy. We use Hoechst33258staining, terminal deoxynucleotidyl transferase mediated deoxyuridine triphosphate nick end labelling (TUNEL) staining to demonstrate apoptotic index(AI) of the placenta cells in all samples. The expression of Smad4and S100B protein in rat placenta was tested by means of immunohistochemistry. Measurement data in groups were assessed by one-way analysis of variance (ANOVA), numeration data in groups were assessed by chi square test.Results①Blood lead levels at the end of pregnancy of the groups with lead exposure were higher than0.483μmol/L, and higher than the control group(F=12.10,P<0.01).②In the groups with lead exposure, Hoechst staining showed hyperchromatic nuclei in placental trophoblast apoptotic cells and compact fluorescent particles in some nucleus; TUNEL assay showed apoptotic cells nucleus staining brown color with some nucleus particles staining brown color. Two assays showed same results:the apoptotic index(AI) of the groups with lead exposure were higher than that of the control group, and the AI of the group with lead exposure during the entire period of pregnancy was higher than the group with lead exposure during the early and late period of pregnancy (P <0.01).③The positive expression of placental Smad4was present in cytoplasm of cytrophoblast, blood capillary and stromal cells. And this expression in lead exposed rats was significantly higher than that in controls (F=10.08,P<0.01). And the groups with lead exposure during the late and entire period of pregnancy were lower than the group with lead exposure during the early period of pregnancy(P<0.05).④The positive expression of placental S100B protein was present in cytoplasm of cytrophoblast, decidual cell and vascular endothelial cell. And this expression in lead exposed rats was significantly higher than that in controls(52.94%), and that of the group with lead exposure during the entire period of pregnancy(93.33%) was higher than the group with lead exposure during the early (87.50%) and late(80.00%)period of pregnancy (χ2=18.62,P<0.05).Conclusions There is a close correlations between apoptosis, Smad4,S100B protein and the level of blood lead of placenta during different periods of pregnancy. So, apoptosis of placenta may play an important role in the pathogenesis of peripartum lead exposure, Smad4and S100B protein take important effects in the development of apoptosis.