The effect of EPO and cEPO on NO production in EPCs. (A) CD34⁺ EPCs were incubated with 50 mU/mL EPO, 50 mU/mL cEPO, or vehicle (Control) for 3 hours before measuring bioavailable NO with DAF-FM diacetate. Shown are the representative results of 10 independent experiments (n ≥ 10). *P < .001 compared with control. (B) EPCs were exposed to EPO () for the indicated time before cell lysis and determination of cGMP intracellular concentration. Shown is the average of 3 different experiments. *P < .026 compared with untreated. (C) RNA was isolated from CD34⁺ EPCs, human EPC colony-forming units, PBMCs, and human liver. After RT-PCR was performed, the PCR products were analyzed on a 1% agarose EtBr gels. The representative results of 2 experiments are shown. (D) Bone marrow cells isolated from wild-type C57/BL6 mice and βC-R knockout mice were grown under conditions that promoted EPC growth. After 1 week, the cells were trypsinized, replated for 24 hours, and pretreated with EPO or cEPO for 3 hours before measurement of bioavailable NO by DAF-FM. Shown are the representative results of 2 independent experiments as mean ± SD (n ≥ 20). *P < .001 compared with control. (E) Bone marrow–derived mice EPC colonies as in panel C were treated with (5μM) bradykinin. Shown is the representative result of 2 different experiments as mean ± SD (n ≥ 15). *P < .001 compared with control.