Abstract: BACKGROUND: In animal experiments regarding stem cells and tissue engineering, immunodeficient nude mice (BALB/c Nude) are of great significance for improving research accuracy. However, the CCl4 concentration and detection time for establishing an acute liver failure model in BALB/c Nude mice are still unclear, which seriously affects the application of this animal model in the study of immunogenic stem cell therapy.
OBJECTIVE: To explore the appropriate CCl4 concentration and detection time for establishing the acute liver failure model in BALB/c Nude mice via intraperitoneal injection in comparison with the C57 model of acute liver failure. 
METHODS: CCl4 at the concentration of 50% was intraperitoneally injected into C57 (n=6) and BALB/c Nude mice (n=6) at the dose of 4 mL/kg. The survival of mice was observed within 72 hours after injection. Then, CCl4 at the concentration of 50%, 20%, and 10% was injected intraperitoneally into BALB/c Nude mice at the dose of 4 mL/kg. The survival of mice was also observed within 72 hours after injection and pathological sections of the liver were made for histopathological observation. According to the optimal concentration of CCl4 in two kinds of mouse models of acute liver failure, 50% CCl4 was injected intraperitoneally into C57 mice and 20% CCl4 was injected intraperitoneally into BALB/c Nude mice. The levels of alanine aminotransferase and aspartate aminotransferase in serum of two kinds of mice were detected before and after injection.
RESULTS AND CONCLUSION: The survival rates of C57 and BALB/c Nude mice were 50% and 0 respectively at 24 hours after CCl4 injection, indicating that the optimal concentration of CCl4 is inconsistent in C57 and BALB/c Nude mice. BALB/c Nude mice injected with 50% CCl4 died in succession within 24 hours. The survival rate of BALB/c Nude mice injected with 20% CCl4 was 66.7% after 24 hours and was still 66.7% after 72 hours. All BALB/c Nude mice injected with 10% CCl4 survived until 72 hours after injection. Pathological results of the BALB/c Nude mouse liver 24 hours after injection showed that the lower concentration of CCl4 indicated the less liver damage, and 20% CCl4 was the most suitable for establishing the acute liver failure model in BALB/c Nude mice. In C57 mice undergoing intraperitoneal injection of CCl4, the levels of alanine aminotransferase and aspartate aminotransferase reached the peak at 4 hours and began to decline at 1 day. In BALB/c Nude mice undergoing intraperitoneal injection of CCl4, the levels of alanine aminotransferase and aspartate aminotransferase reached the peak at 1 day and began to decline at 3 days. All these findings indicate that to improve the reliability of animal experiments, 50% CCl4 should be selected when making the acute liver failure model in C57 mice, and intervention measures should be taken 4 hours after injection. When BALB/c Nude mice are used to make the acute liver failure model, 20% CCl4 should be selected and intervention measures should be taken at 1 day after injection.

Key words: carbon tetrachloride, acute liver failure, BALB/c Nude mouse, C57 mouse, model