Objective To explore the influence of endoplasmic reticulum stress on fatty liver in mice feeding with high-fat diet.Methods The 8-week-old male C57BL/6J mice were randomly divided into two groups:high-fat diet group (with 60％ calories by high saturated fatty acid) and control group (with chow diet),both groups had been fed for 16 weeks.H&E-staining and Sudan Ⅳ-staining reflected lipid deposition in liver.The levels of 78-kDa glucose-regulated protein (GRP78),protein kinase R-like endoplasmic reticulum kinase (PERK),phosphorylated α subunit of eukaryotic initiation factor 2 (p-eIF1 α),C/EBP homologous protein (CHOP),steroid regulated element binding proteins 1 (SREBP-1),and fatty acid synthetase (FAS) protein were determined by Western blot to reflect the endoplasmic reticulum stress and lipid synthesis.Results In liver of high fat diet (HFD) group,H&E staining showed that the cytoplasm of hepatocytes were filled with vacuoles,Sudan Ⅳ staining also displayed that many different sizes of red lipid drops exist in hepatocytes.Compared to the liver of control group,high-fat diet induced endoplasmic reticulum stress and elevated lipid synthesis,as evidenced by increases in the level of peroxisome proliferator-activated receptor alpha (PPARα) mRNA expression,and the protein levels of GRP78,PERK,phosphorylated eIF2α,CHOP were also significantly increased.In primary normal hepatocytes incubated with exogenous oleic acid intervention for 24-72 hours,the expression of GRP78,PERK,phosphorylated eIF2α,CHOP protein levels,and the expression of SREBP-1 and FAS protein were significantly increased in dose-dependent manner.Conclusions Feeding with high-fat diet led to accumulation of lipid deposition in liver and fatty liver,the underlying mechanisms might be related to induction of endoplasmic reticulum stress.