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Dogs were placed on total cardiopulmonary bypass and the anterior descending branch of the left coronary artery was occluded for the duration of 15 min, 60 min or 90 min. In some experiments the coronary perfusion was restored after the occlusion. Fragments of sarcoplasmic reticulum were isolated from ischemic and nonischemic cardiac tissue and the Ca 2+ transport mechanism of the reticulum was studied. The Ca 2+ uptake of reticulum fragments obtained from cardiac tissue ischemic for 15 min was not impaired compared to the nonischemic control hearts. However, ischemia for 60 or 90 min caused impairment of Ca 2+ uptake by the sarcoplasmic reticulum isolated from the ischemic tissue. The functional damage brought by coronary occlusion for 60 min could be reversed by the restoration of coronary circulation after the occlusion, but after occlusion for 90 min it was irreversible.
Lee et al. (1967) studied this question.