Myocardial stunning (temporary post-ischaemic contractile dysfunction) may be caused by oxidative stress and/or impaired myocyte Calcium homeostasis. Regional myocardial stunning was induced in open-chest pigs (segment shortening reduced to 68.3 +/- 4.7% of baseline) by repetitive brief circumflex Coronary occlusion (1/R). Reduced glutathione was depleted in stunned rnyocardium (1.34 +/- 0.06 vs. 1.77 +/- 0.11 nmol/mg, p = 0.02 vs. remote myocardium) indicating regional oxidant stress, but no regional differences were observed in protein-bound 3-nitrotyrosine or S-nitrosothiol content. Repetitive 1/R did not affect myocardial quantities of the sarcolemmal sodium-calcium exchanger, L-type channel, SR calcium ATPase and phospholamban, or the kinetics of ligand binding to L-type channels and SR calcium release channels. However, initial rates of oxalate-supported Ca-45 uptake by SR were impaired ill stunned myocardium (41.3 +/- 13.5 vs. 73.0 +/-15.6 nmol/min/mg protein, p = 0.03). The ability of SR Calcium ATPase to sequester cytosolic calcium is impaired in stunned myocardium. This is a potential mechanism Underlying contractile dysfunction. (C) 2009 Elsevier Inc. All rights reserved.