[Changes in myocardial energy charge following cardiac arrest and subsequent resuscitation]

Cardiac resuscitation becomes more difficult as time of arrest is prolonged. This study was designed to investigate changes in energy charge (EC) during cardiac arrest and subsequent resuscitation periods. The experiment was divided into 2 parts. In the first part, 36 rats were divided into 6 groups. Control rats were anesthetized only with pentobarbital and the heart was extirpated. In other rats, an acute exsanguination was carried out until mean arterial pressure (MAP) fell to 0, and then the rats were divided into 5 groups according to the time of extirpation following the cardiac arrest: 1, 5, 10, 15 and 20 minutes, respectively. The extirpated hearts were rapidly frozen with liquid nitrogen. ATP, ADP and AMP were enzymatically measured and EC was calculated. ECG was monitored to ascertain complete electrical arrest. Disappearance of ECG activity was observed about 9 minutes after MAP reaching zero. In the second part; 36 rats were also divided into 6 groups. After the same manipulation as in the first part, the extirpated heart was perfused for 30 minutes using Langendorff method and both cardiac function (LVP, LV dp/dt and HR) and EC were investigated. Total adenine nucleotide (TAN) was already diminished at 1 minute and decreased progressively. On the contrary, EC was well maintained around control level until ECG activity disappeared completely, and an abrupt decrease in EC occurred after electrical arrest. When the heart was perfused about 30 minutes, EC recovered almost to the control level in the groups in which perfusion was started within 10 minutes, but its recovery was incomplete in the groups in which perfusion was begun after 10 minutes.(ABSTRACT TRUNCATED AT 250 WORDS)