Recent reports suggest that brief periods of low-flow ischemia (lf Isc) and reperfusion (R) before prolonged Isc mimic ischemic preconditioning (IPC) in murine hearts, probably by a preservation of high energy phosphates.

In order to test this hypothesis, Langendorff-perfused isolated rabbit hearts were subjected to 45 min lf Isc (5% of baseline perfusion flow) with lf IPC or not, followed by 120 min R. lf IPC was induced by a single episode of 5 min lf Isc and 10 min R. These were compared with IPC hearts by 5 min no-flow Isc and 10 min R.

If IPC as well as IPC enhanced post-ischemic functional recovery although IPC did not reduce infarct size (Isc control, 37.5±3.1, IPC, 16.2±1.5, lf Isc, 43.0±0.7, and lf IPC, 40.4±1.0% of the left ventricle). Myocardial ATP hydrolysis and lactate production during the preischemic, ischemic, and reperfusion periods were not differ between the experimental groups.

These results suggest that a brief period of lf Isc could not precondition the rabbit heart and the energy metabolism hypothesis may not be a universal mechanism for the cardioprotective effect of IPC.