FIGURE 1.

NHE-1 protects cells against irradiation-induced cell death in an acidic environment. (A) Cell cycle distribution of CCL39 cells treated (+) or not (-) with 100 μM of the NHE-1 inhibitor (HOE#694) in normoxia in a ${\text{HCO}}_3^{-}$/CO₂-free environment at pH_o 7.5 or 7.0 for 24 h. (B,C) CCL39 cells (1 × 10⁴) were plated in 60 mm dishes. Once attached cells were incubated in a ${\text{HCO}}_3^{-}$-free medium adjusted to pH_o 7.5 or 7.0, and treated in the presence (+) or absence (-) of 100 μM of NHE-1 inhibitor (HOE#694) for 24 h in a CO₂-free atmosphere. Dishes were then irradiated (0, 2, 4, 6, 8, and 10 Gy) and returned to a 5% CO₂ incubator with fresh ${\text{HCO}}_3^{-}$-containing medium for 4 days. Cell death was determined by the trypan blue exclusion assay.