Fig. 6.

Exposure to a proton carrier (CCCP; 20 μM) reduces cell viability assayed 2–4 days later. Viability was measured as Alamar blue reducing activity (see materials and methods) normalized to values measured in sister cultures not exposed to CCCP or high [K⁺]. For results indicated by open bars, sister cultures were exposed for 5–60 min to CCCP in normal medium and assayed 4 days later. For results represented by hatched bars, sister cultures were all exposed to a high-[K⁺] medium for 60 min (in mM: 145 KCl, 20 NaHCO₃, 5 glucose, 80 sucrose, and 1 BAPTA), during which some cultures were also exposed to CCCP for the indicated times. Cultures were washed thoroughly with normal medium at the end of the CCCP and/or high-[K⁺] exposure and assayed 2 days later. *P < 0.05, significant difference from sister cultures not exposed to CCCP or high [K⁺] (Dunnett's test for multiple comparisons). The illustrated findings were confirmed in 2 additional experiments.