Suppression of stress proteins in endoplasmic reticulum in liver cytosol of rats treated with a highly toxic coplanar PCB

The present study was addressed on the effect of 3,3',4,4'5- pentachlorobiphenyl (PenCB) to the expression of glucose regulated protein (GRP) 78 and GRP94 in liver endoplasmic reticulum of rat by treatment with the schedule after acute or subacute exposure. In the acute exposure, male Wistar rats received PenCB in corn oil at once a dose of 25 mg/kg i.p., then at 5 days after treatment the microsomes were prepared. Free- and pair-fed control groups were given the vehicle. The microsomal proteins were separated on SDS-PAGE, transferred to membrane and blotted using anti-sera to the GRPs. The reduction of GRP78 and GRP94 was associated significantly with the acute exposure. In subacute exposure, the rats received PenCB in corn oil at once a dose of 0.1 or 1.0 mg/kg i.p. At 4 weeks after treatment, liver microsomes were obtained. The expression level of GRP78 and GRP94 are also decreased at 1.0 mg PenCB/kg treatment as similar as the acute exposure. But the reduction was not notable at 0.1 mg PenCB/kg treatment. GRP78 and GRP94 are a member of GRPs and the expression is regulated by glucose in cells as stress proteins. GRP78 and GRP94 have also the function for chaperone protein. Chaperone proteins have important physiological functions against synthesized and/or denatured proteins, which include assembling, folding of proteins. Our results suggested that a part of the toxicity of PenCB is associated to significant decrease of the chaperone proteins in the endoplasmic reticulum.