Myocardial enzyme release from ischemic isolated perfused working rat heart

Isolated working rat hearts were made ischemic for 5, 10, and 30 minutes respectively. After the ischemic period, all hearts were perfused in a retrograde nonworking way for 30 minutes. During the 5 first minutes of ischemia, there was a marked fall of cardiac output and coronary flow. A significant release of GOT was seen and this was more marked after longer periods of ischemia. Addition of adrenaline to the perfusate increased the enzyme release. Pacing at 400/minute, high preload, high afterload, acidosis, or alkalosis did not alter enzyme release. Glycogen, ATP and CrP levels were depressed at the end of the ischemic period, but were seen to be rising again during the retrograde perfusion. This study indicates that myocardial tissue may release enzymes without being irreversibly damaged.