Lack of effect of IFNγ on decay of SCF and EP receptor mRNA after actinomycin D treatment. Day-6 cells were incubated with (•) or without (○) 2,500 U/mL rhIFNγ for 3 hours and then RNA synthesis was inhibited with actinomycin D (5 μg/mL). Total RNA was extracted at the indicated time periods for Northern analysis. The membrane was hybridized sequentially with SCF (A) and EP (B) receptor ³²P-DNA probes, as well as a probe for actin, and densitometry was performed with correction for loading variations. The purity of control cells was 48% ± 3% and the purity of rhIFNγ-treated cells was 46% ± 2% (mean ± SD of 3 experiments).