Cytochrome induces apoptosis in metabolically quiescent cells. Forward/side-scatter plots (gate A) and DNA histograms of A15 cells quiesced for 24 hours without IL-3 then electroporated with bovine cytochrome c at 80 μg/mL. In growing cells, IL-3 was present throughout all manipulations. DNA analysis was performed after 2 hours. (a) Cells growing in IL-3. (b) Cells quiesced for 24 hours. (c) Growing cells electroporated with FCS. (d) Growing cells electroporated with 80 μg/mL bovine cytochrome c. (e) Quiesced cells electroporated with FCS. (f) Quiesced cells electroporated with 80 μg/mL cytochrome c. Gates B through E set for pre-G1, G1, S, and G2/M. The left shift in (b) is due to cell contraction. Note the pre-G1 apoptotic DNA, broadening of G1 with right shoulder in quiesced cells, and reduction in G2/M in cells electroporated with cytochrome c. Apoptosis induced by cytochrome c by direct microscopy was as follows: growing, 51%; quiesced, 43%. Controls showed less than 3% apoptosis.