Chelation of GRP78 with lead and its localization changes in the astroglia of rats exposed to lead

To observe the chelation of GRP78 with lead (Pb) and its localization changes, astroglial cells from Wistar rat brain were primarily cultured in medium with acetate Pb. The processes were terminated at different time points. The immunoprecipitation (IP) and Western blotting were used for GRP78 purification and expression and the Pb concentration was determined by employing atomic absorption spectrophotometry (AAS). The localization change of GRP78 was observed with colloid gold immunoelectron microscopy. The results showed that the expression of GRP78 was increased significantly in the cells treated with 1.0 mu mol/L acetate Pb for 24 h and peaked at 96-192 h (P < 0.01), and at the 12th day, the expression of GRP78 began to decrease but was still higher than normal (P < 0.05). Pb content started to increase when cells were treated by acetate Pb for 24 h, and the peak appeared at 8 day (P < 0.01), and then Pb content decreased gradually, but was still higher than normal (P < 0.05). GRP78 protein expression began to remarkably increase when it transferred from ER to the cytosol around the nuclei 24 h after treatment with Pb. It is concluded that GRP78 in astroglia could strongly chelate with Pb ions and it might be a target protein of Pb.