MKs express functional IGF-1R. (A) Immunoblotting analysis of IGF-1R, IRS-1, and IRS-2 in human and mouse MKs. (B-C) Association of IRS-1 and IRS-2 with IGF-1R in human and mouse MKs after treatment with or without 100 ng/mL rhIGF-1 for 15 minutes. Lysates were subjected to immunoprecipitation with antibody against IGF-1R, and were immunoblotted with antibodies against p-Tyr, IRS-1, IRS-2, or IGF-1R. (D-F) Real-time PCR (RT-PCR) (D) and immunoblot analysis of IGF-1R expression (E-F) in human MKs at the same counts, primary MKs were cultured from CD34⁺ cells cultured with 20 ng/mL TPO for 7, 10 and 14 days. Human MKs or mouse MKs were purified after being labeled with CD41 antibody. *P < .05, **P < .01, vs the expression level at day 7.