IR induces dose-dependent cell death in Reh cells that can be inhibited by forskolin. (A) Reh cells were irradiated with the indicated doses of IR and cultured for 24 hours before cell death analysis by PI staining (n = 4). (B) Reh cells were treated with the indicated doses of forskolin or solvent (dimethyl sulfoxide corresponding to 60 μM forskolin) 30 minutes before irradiation with 10 Gy. After 24 hours of incubation, cell death was assessed by PI staining (n = 4). *P < .01 relative to cells treated with IR only. (C) Reh cells were treated with or without IBMX, forskolin, or 8-CPT-cAMP for 90 minutes (IBMX) or 45 minutes (forskolin, 8-CPT-cAMP) before exposure to 10 Gy IR. After 18 hours, cells were analyzed for PI uptake, annexin V binding, and TUNEL positivity by FACS (n = 4). *P < .01 relative to cells treated with IR only.