EPO as well as GM-CSF induces a transient reduction in the level of EPOR mRNA in UT-7 cells. The effects of EPO and GM-CSF on the expression of EPOR mRNA in UT-7 cells was examined by RNA blot hybridization analysis. Logarithmically growing cells were deprived of growth factors for 16 hours in IMDM containing 10% FBS and then stimulated with 10 U EPO/mL (A) or 10 ng GM-CSF/mL (B). The total cellular RNA was isolated from the cells at the time points indicated. RNAs (20 μg/lane) were electrophoresed on a formaldehyde/agarose gel. The RNAs were then transferred to a nylon membrane and hybridized to ³²P-labeled human EPOR cDNA as a probe. (C) Densitometric analysis of the data presented in (A) and (B). The amounts of the mRNAs were quantitated and normalized to β-actin mRNA levels.