Reversal of MPA-induced apoptosis by guanosine in 32D cells. Cells were cultured without (lane 1) or with (lanes 2 to 7) 2 μM MPA. At beginning of the culture 100 μM guanosine (lane 3), 100 μM adenine (lane 4), 20 μM adenosine (lane 5), 100 μM cytidine (lane 6), or 100 μM uridine (lane 7) was added. ELISA was used to measure apoptosis after 24 hours of treatment. Data are from 1 representative experiment assayed in triplicate. Similar reversal by guanosine has been documented at least 5 times in 32D cells and in BaF3 and FL5.12 cells.