Fig. 1. Graphical presentation of the experimental protocols used to examine cardiac performance in oxygenated and anoxic in situ perfused trout hearts. Output pressure (P_out) is represented by the solid line, and the two maximal performance tests are shown as the progressive increases in P_out. The anoxic exposure is shown with grey bars. During both routine oxygenated and anoxic conditions, P_in was adjusted to as much as 0.25 kPa to maintain cardiac flow rate () at 12, 16, 20 or 24 ml min^-1 kg^-1 at 5, 10, 15 and 18°C, respectively. Arrows indicate samples for lactate measurements of the perfusate.