Objective To Study the pathogenesis of placenta toxicity of lead exposure during different gestation period by observing the pregnant outcome and testing the expression of matrix metalloproteinase-9(MMP-9)and tissue inhibitor of metalloproteinase-1(TIMP-1)in placenta.
Methods Total of 108 Wistar rats divided into four groups with 27 each randomly. Sex ratio was 2:1(male/female). Fed with 0.025% lead acetate solution, ad libertum, during different period of gestation. Group A were fed with 0.025% lead acetate in early gestation(1-10 d). Group B were fed with 0.025% lead acetate in late gestation (11-20 d). Group C were fed with 0.025% lead acetate throughout whole gestation (1-20 d). Atomic absorption spectrophotometer was used to measured the blood lead concentration at end of pregnancy. The pregnant rats were necrospied at the end of gestation(three weeks)under aenesthia. Placenta were observed and blood sample was taken from abdominal vein. The number of pups, their body weight、body length、tail length、placenta weight were measured. The expression of MMP-9 and TIMP-1 in rat placenta was tested by means of immunohistochemistry.
Results The blood lead level of experimental groups was significant different(P < 0.01)versus the blood lead level of control. There were significant differences among placenta weight, body weight of pups, body length and tail length of pups in different groups (P < 0.01). Among them experimental group C was the lowest (0.31& #177;0.13)g,(2.08& #177;0.88)g,(2.37& #177;0.32)cm,(0.98& #177;0.09)cm. Maternal blood lead level was negatively correlated to placenta weight(r=0.652, P < 0.01). The expression of MMP-9 was significantly reduced and TIMP-1 was significantly increased versus the control group.
Conclusion Lead exposure to rat during different gestation period lead to different pregnant outcome. Lead exposure throughout the gestation cause the highest blood lead concentration at the end of the pregnancy, and the placenta, pups were most seriously effected. Changing of the MMP-9 and TIMP-1 expression in placenta may play one of the roles in pathogenesis of placenta toxicity of lead exposure.
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