Lead exposure during different periods of pregnancy in placental apoptosis in rats

Abstract

Objective To investigate the effects of lead exposure on rat placental apoptosis during different periods of pregnancy. Methods All Wistar rats were randomly divided into four groups with 27 for each group with the sex ratio of 2 : 1 (female : male). The groups with lead exposure consumed water with 0. 025％ lead acetate during the entire, early or late period of pregnancy. Controls were given distilled water without lead. Blood lead levels were determined by atomic absorption spectrophotometry at the end of pregnancy. Placental apoptosis were assessed by both Hoechst staining and terminal deoxynucleotidyl transferase-mediated dUTP nick end labelling (TUNEL) assay. Data were assessed by one-way analysis of variance, and differences between groups were compared by q-test. Results Blood lead levels at the end of pregnancy of the groups with lead exposure (entire, early or late pregnancy) and the control group were (1. 74±0. 19) μmol/L,(1.27±0.26) μmol/L, (0.60±0. 11) μmol/L and (0.04±0.01) μmol/L respectively(F= 12. 10,P＜0.01). In 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 brown-staining apoptotic cells nuclei with some nuclei particles staining brown. Two assays showed the same results: the apoptotic index of the groups with lead exposure were higher than that of the control group; the apoptosis index of the group with lead exposure during entire pregnancy was higher than that of the group with lead exposure during early and late pregnancy (P ＜ 0. 05).Conclusions Lead exposure during pregnancy could elevate the blood levels of lead and the degree of placental apoptosis. Key words: Lead poisoning; Placenta; Apoptosis; Pregnancy; Rats