Hepatocyte proliferation in vivo was determined using the bromodeoxyuridine (BrdU) incorporation assay. Mice were injected (IP) with BrdU (50 μg/g body weight) and euthanized 2 hours later, and the livers were harvested for IHC staining of BrdU using a kit (BD Biosciences). The percentage of BrdU-labeled hepatocytes in each slide was counted in five low-power (×100) fields. Data represent mean ± SEM (n = 3). *P < 0.05.