Wistar rat lung tissue respiration, ATP content and caspase activity in oxygenated MEM. Lung fragments were incubated at 37°C in 50 mL MEM (continuously gassed with 95% O2: 5% CO2) for up to ~7 h. At indicated time periods, samples were removed from the incubation medium and processed for measurements of O2 consumption, ATP content and caspase activity. Panel A: Runs of cellular mitochondrial O2 consumption are shown; t = 0 corresponds to animal sacrifice. The rate of respiration (k, μM O2 min-1) was set as the negative of the slope of [O2] vs. t. The values of k
(μM O2 min-1 mg-1) are shown at the bottom of each run. Panel B: The values of k
and ATP are plotted as a function of incubation time. Panel C: HPLC runs of caspase activity at 0, 2, 4 and 6 h of incubation. The retention time (Rt) for Ac-DEVD-AMC was ~2.5 min and AMC ~4.8 min (insert, reflecting caspase activity). The substrate run (dashed line) was sample incubated at 37°C without lung specimen for 6 h. Panel D: AMC peak areas are shown as a function of incubation period.