〔Abstract〕 Objective To explore the effects of inhibition of the inositol 1,4,5-trisphate receptor(IP3R)-Ca2+pathway on acetaminophen(APAP)-induced liver injury in mice and its mitochondrial-associated endoplasmic reticulum membranes(MAMs). Methods 40 SPF-rated male C57BL/6 mice were randomly divided into control group(n=10),model group(n=10),IP3R inhibitor(2-aminoethoxydiphenyl borate, 2-APB)group(n=10) and the Ca2+chelator [1,2-bis(2-aminophenoxy) ethane-N,N,N′N′-tetraacetic acid, BAPTA-AM] group(n=10).Mice in the model group, 2-APB group, and BAPTA-AM group were given a single intraperitoneal injection of APAP(300 mg/kg).Half an hour before APAP injection, mice in the 2-APB group were injected intraperitoneally with 2-APB(20 mg/kg) and mice in the BAPTA-AM group were injected intraperitoneally with BAPTA-AM(2.5 mg/kg).The mice in each group were executed 24 hours after intraperitoneal injection of APAP.Serum alanine aminotransferase(ALT) and aspartate aminotransferase(AST) were measured by chemical method. The pathological change of liver was observed by HE staining.The ultrastructural changes of mitochondria, endoplasmic reticulum and MAMs in liver cells were observed by transmission electron microscopy.The changes of Ca2+in liver tissue homogenate were measured by calcium assay kit.The protein expression levels of mitofusin 1(MFN1),mitofusin 2(MFN2),inositol 1,4,5-trisphate receptor(IP3R1),glucose regulated protein 75(GRP75) were detected by Western blot. Results Compared with the control group, the serum ALT and AST in the model group increased(P<0.01).Disorganized hepatocyte arrangement, hepatocyte degeneration and lobular central necrosis were observed.Breakage and disappearance of mitochondrial cristae, swelling and fracture of the endoplasmic reticulum and increase of the number of MAMs were also observed by transmission electron microscopy.The Ca2+level in liver tissue homogenate increased(P<0.01).MFN1 and MFN2 protein expression decreased(P<0.01),IP3R1 and GRP75 protein expression increased(P<0.01).Compared with the model group, the serum ALT and AST in 2-APB group and BAPTA-AM group decreased(P<0.01),the liver pathological changes were significantly improved, MAMs decreased, the content of Ca2+in liver homogenate decreased(P<0.01),MFN1 and MFN2 protein expression increased(P<0.01),IP3R1 and GRP75 protein expression decreased(P<0.01). Conclusion Inhibition of the IP3R-Ca2+pathway protects against APAP-induced liver injury in mice. Its mechanism is related to reducing hepatic Ca2+levels, reducing the number of MAMs, and regulating the expression of MAMs-related proteins.