Liver weight/total body weight ratios and BrdU staining in WT and IL-6 knockout mice after 70% hepatectomy with and without SCF treatment. Liver weight/total body weight ratios and BrdU staining as an estimate of hepatocyte proliferation were measured in mice over time. Four treatment groups were studied: WT + vehicle, WT + SCF, IL-6 knockout + vehicle, and IL-6 knockout + SCF. (a) Beginning 72 hours after hepatectomy, liver weight/total body weight ratios in IL-6 knockout mice treated with vehicle are significantly decreased compared with the other three treatment groups, and this difference continues to 120 hours. *P < 0.05, IL-6 knockout + vehicle vs. all other groups. There was no significant difference noted between IL-6 knockout mice treated with SCF and WT animals treated with vehicle or SCF. Data are expressed as mean ± SEM. (b) At 36 hours after hepatectomy, there was a significant increase in hepatocyte proliferation in IL-6 knockout animals treated with SCF (^#P < 0.05 vs. all other treatment groups). At 48 hours of incubation, the proliferation measured in IL-6 knockout animals treated with vehicle was significantly decreased compared with all other treatment groups (*P < 0.01 vs. all other groups). By 60 hours after hepatectomy, proliferation in IL-6 knockout mice treated with vehicle was still significantly decreased compared with WT animals treated with vehicle or SCF (**P < 0.05 vs. WT + vehicle and WT + SCF); however, there was no longer a difference between IL-6 knockout mice treated with vehicle and IL-6 knockout mice treated with SCF.