Objective    To investigate the relationship between endoplasmic reticulum stress induced by proteinuria and apoptosis of renal proximal tubular epithelial cells in chronic kidney disease (CKD).     Methods    Twenty-one patients with CKD were included. According to 24-hour urinary protein excretion

they were grouped by three levels: 1.5 g/24 h

1.5-3.5 g/24 h

3.5 g/24 h. The control tissues were pathologically confirmed as normal renal tissues adjacent to the renal tumors. Immunohistochemistry was performed to detect the protein markers of endoplasmic reticulum of renal proximal tubular epithelial cells-oxygen-regulated protein150 (ORP150) and glucose-regulated protein 78 (GRP78)

and TUNEL was used to detect the apoptosis of the epithelial cells. The correlation of proteinuria levels with ORP150

GRP78 or apoptosis index was determined.     Results    The expressions of ORP150 and GRP78 in endochylema of renal proximal tubular epithelial cells both increased dramatically in the CKD patients (P0.01). They also showed significant difference among the patients of three levels of proteinurea (P0.01)

and had positive correlation with proteinuria levels (r=0.695

r=0.76

P0.01). The apoptosis indexes showed significant difference among the three levels of proteinurea

and had positive correlation with proteinuria levels (r=0.835

P0.01).     Conclusion    Endoplasmic reticulum stress and apoptosis of renal proximal tubular epithelial cells exist in CKD

and showed positive correlations with proteinurea. Endoplasmic reticulum stress may be essential in the apoptosis of renal proximal tubular epithelial cells induced by proteinuria.