Objective: To observe the effect of Gegen Tongmai Yin on the endoplasmic reticulum stress related C/EBP-homologousprotein (CHOP) expression induced by homocysteine (HCY)

in order to discuss anti-atherosclerosis (AS) molecular mechanism. Method: Thirty-six rabbits were randomly divided into 6 groups

the normal control group (the normal feed)

the high-fat group (the normal feed+1% cholesterol+0.02% methionine)

the rosuvastatin group (1 mg·kg-1+high-fat feed)

the Gegen Tongmai Yin low

middle and high dose group (5

7.5

10 g·kg-1+high-fat feed).The rabbit AS model was induced by feeding the high-fat diet for 9 weeks. The superior segment of thoracic aorta was taken for the pathological observation

the CHOP expression was detected by situ hybridization and Western-blotting hybridization. Result: Pathological observation showed that the typical lipid plaque formed under the tunica intima in high-fat group

the pathological changes in the Rosuvastatin group were weaker than high-fat group

with small lipid plaque formed. The lipid plaque only formed in local areas in the Gegen Tongmai Yin low-dose group

the tunica intima structural disordered in the middle-dose group

only a small quantity cellular proliferation of smooth muscle in the high-dose group. Tissue in situ hybridization detection showed that CHOP gene expressed in the cytoplasm of tunica intima and tunica media in all groups. Small brownish yellow granules appeared in the endothelial cells and smooth muscle cells in normal control group. The brownish yellow granules were strongly expressed in the smooth muscle cells and foam cells in the high-fat group. The positive signal decreased expression in the smooth muscle cells in Gegen Tongmai Yin groups compared with the high-fat group. Western-blotting hybridization showed that CHOP protein were all expressed in 6 groups

CHOP protein expression increased in high-fat group compared with normal group. The difference was statistically significant(P<0.01);CHOP protein expression decreased in Gegen Tongmai Yin low

middle and high dose groups

the difference was significant(P<0.01). Conclusion: The Gegen Tongmai Yin's anti-AS mechanism may be correlated with the CHOP expression. The Gegen Tongmai Yin can improve the injury of blood vessel induced by HCY and depress the CHOP expression in the rabbit's thoracic aorta.