Protein tyrosine phosphorylation in normal and PV ECFC after incubation with EP or SCF. Day-8 cells were incubated at 37°C with medium, rhEP at 20 U/mL, rhSCF at 100 ng/mL, or rhEP plus rhSCF for 10 minutes. The cells were then lysed and immunoprecipitated with anti-pTyr antibody for SDS-PAGE. -P h o s p h o t y r o s i n e - c o n t a i n i n g -proteins were identified by immunoblotting with anti-pTyr antibody. The purity of the ECFC was 74% ± 5% (normal) and 77% ± 4% (PV).