Myocardial stress can result in myocellular phenotypic changes including enhanced activity of
antioxidant enzyme systems. Accordingly, endogenous tissue
antioxidant enzyme activity has been associated with resistance to cardiac
ischemia and
reperfusion injury. The present study was designed to determine if environmental perturbations could alter myocardial
antioxidant enzyme (
catalase) activity and function after
ischemia. Isolated perfused rat hearts (Langendorff apparatus, 37 degrees C) were subjected to 20 min global
ischemia (37 degrees C) and 40 min reperfusion. Rats studied immediately following shipment had increased myocardial
catalase activity (1330 +/- 3.5 U/g, P < 0.05 vs quarantined control) and increased resistance to
ischemia and
reperfusion injury (end reperfusion developed pressure, DP 55 +/- 4.0 mm Hg, P < 0.05 vs quarantined control). However, control rats that were quarantined for 4 weeks exhibited a progressive decrease in
catalase activity (760 +/- 10 U/g) for 3 weeks of quarantine. There was a concurrent decrease in resistance to
myocardial ischemia and
reperfusion injury (DP 40 +/- 3.6 mm Hg). Similarly, quarantined rats subjected to construction-related noise levels in excess of 90 dB (A scale) had increased myocardial
catalase activity (1140 +/- 3.3 U/g, P < 0.05) and functional tolerance to
ischemia and reperfusion (DP 66 +/- 3.3 mm Hg, P < 0.05). Finally, rats experiencing 90-dB noise levels for 2 days exhibited increased myocardial
catalase activity (1125 +/- 30 U/g, P < 0.05) and
myocardial ischemia and
reperfusion injury tolerance (DP 62 +/- 1.7 mm Hg, P < 0.05). We conclude that variations in environmental conditions can relate to changes in
antioxidant defense mechanisms and tolerance to
myocardial ischemia and
reperfusion injury in the rat.