Mitochondrial respiratory complexes activities. Submitochondrial particles prepared from the four animal groups were analyzed for Complex I–III activity (A), Complex II–III (B), or Complex IV (D). The ratio of Complex I–III to Complex II–III activities is shown as a surrogate of isolated Complex I activity (C). CA8, 8 min of cardiac arrest prior to resuscitation; R30, 30 min post-ROSC; R60, 60 min post-ROSC; *p <.05, n = 3 in each group.