We studied the cardiac protective qualities of
zinc in the postischemic isolated rat heart. Hearts, perfused with
Krebs-Henseleit buffer with or without
zinc-bis-histidinate, were subjected to 20 min of "no-flow" normothermic global
ischemia. Pre- and postischemic treatment with 0, 10, 20, or 30 microM
zinc resulted in concentration-dependent enhancement of postischemic function as evidenced by decreased end-diastolic pressure (37 +/- 3, 25 +/- 5, 17 +/- 5, and 8 +/- 2 mmHg, respectively) and increased recovery of developed systolic pressure (41 +/- 6, 59 +/- 17, 76 +/- 18, and 87 +/- 16 mmHg, respectively) and maximum rate of rise in pressure (+dP/dtmax; 823 +/- 141, 1,413 +/- 396, 1,700 +/- 450, and 2,157 +/- 407 mmHg/s, respectively) as well as decreased
lactate dehydrogenase efflux from the hearts (peak: 1,002%, 840%, 580%, and 440%, respectively). Only preischemic treatment resulted in an intermediate protective effect, whereas treatment starting at reperfusion worsened postischemic damage. In hearts perfused with
zinc throughout the experiment, prolongation of the preischemic treatment interval further enhanced postischemic recovery. With the use of
salicylate as a trap for .
OH, it was determined that
zinc virtually eliminated the early postischemic "burst" of this species normally observed in this preparation. Atomic absorption studies demonstrated that hearts treated with 30 microM
zinc contained 27% less
copper than control hearts by the end of the reperfusion period. In control hearts, electron microscopy revealed swollen mitochondria with marked loss of inner matrix density, whereas morphology of postischemic
zinc-treated hearts was essentially normal. These studies indicate that
zinc possesses cardiac cytoprotective qualities and support the concept that this
metal can decrease .
OH formation by affecting
copper reactivity.