hGH enhances dTMP-induced platelet production. (A-B) Western blot analysis of p-STAT5 and p-ERK1/2 in whole-cell lysates from M07e cells after exposure to rhTPO (20 ng/ml) or rhGH (100 ng/ml) for the indicated times. (C) Western blot analysis of p-ERK1/2 in whole-cell lysates from human cord blood-derived CD34⁺ cells cultured with rhTPO (20 ng/ml) for 6 days, and treated with rhTPO (20 ng/ml) or rhGH (100 ng/ml) for the indicated times after starvation. (D) Human cord blood-derived CD34⁺ cells were cultured with rhGH (100 ng/ml) in the presence of rhSCF (20 ng/ml) for 7 days; then the cells were further treated with rhGH (100 ng/ml) for another 3 days with or without U0126 (10 μM) in the culture. Histogram showing the percentage of CD41⁺CD42b⁺ megakaryocytes from 3 independent experiments analyzed by flow cytometry. Error bars denote SD. (E) Western blot analysis of p-ERK1/2 (i) and p-Akt (ii) in whole-cell lysates from human cord blood-derived CD34⁺ cells cultured with rhTPO (20 ng/ml) for 11 days, and then treated with rhTPO (20 ng/ml) or rhGH (100 ng/ml) for the indicated times after starvation. (F) Western blot analysis of p-Akt in whole-cell lysates from Meg-01 cells after exposure to rhTPO (20 ng/ml) or rhGH (100 ng/ml) for the indicated times. (G) Human cord blood-derived CD34⁺ cells were cultured with rhTPO (20 ng/ml) for 7 days and then treated with rhGH (100 ng/ml) with or without U0126 (10 μM) or LY294002 (20 μM) for another 3 or 6 days. (i) Proplatelet-forming megakaryocytes were counted in each well 3 days later. (ii) Culture-derived platelets were analyzed 6 days later. Mean ± SD of 3 experiments. **P < .01. (H) Western blot analysis of the activation of ρ GTPases, RhoA (i), Rac1 (ii), and Cdc42 (iii) in whole-cell lysates from human cord blood-derived CD34⁺ cells cultured with rhTPO (20 ng/ml) for 7 days, and then treated with rhGH (100 ng/ml) for 3 days with or without LY294002 (20 μM).