Effect of HAPO on the survival rate of irradiated mice. (A) Survival curves of BALB/c mice after irradiation with 6.0 Gy (93% lethal dose). The 16 mice in each group received a daily subcutaneous injection of rhHAPO at doses of 5 μg, 10 μg, or 15μg for 14 days. The control mice received the same volume of PBS injected according to the same schedule. The irradiated mice started to die after 6 days. The administration of rhHAPO increased the survival rate in a dose-dependent manner, with 100% protection at a dose of 15 μg/d. (B) Quantitative changes of bone marrow and peripheral blood cells of the mice after irradiation. The 16 mice in each group received a daily subcutaneous injection of rhHAPO (10 μg) or PBS. At each time point, 3 mice in each group were randomly sampled and were subjected to examination for the content of the bone marrow CD34⁺ cells from the murine femurs (i) and the quantitative changes in the number of white blood cells (ii), platelets (iii), and red blood cells (iv) in the blood of the mice after irradiation. Data are represented as the mean ± SD. ^*P < .05 versus control.