[Exogenous adenosine and postischemic dysfunction in the isolated rabbit heart].
It is recognized that adenosine lessens the systolic alterations of the postischemic ventricular dysfunction ("stunned myocardium"), but little is known about the drug's effects on the diastolic phase of the cardiac cycle. The aim of this work was to determine the effect of adenosine when it was administered: a) before ischemia and during reperfusion, and b) from the early reperfusion period to the end of the experiment on the systolic and diastolic function of the "stunned myocardium". An additional objective was to determine whether adenosine modifies the release of creatine phosphokinase (CPK) and lactate dehydrogenase (LDH), in the "stunned myocardium". Rabbit isolated isovolumic hearts were perfused according to Langendorff's technique, and subjected to 15 minutes global ischemia and 30 minutes reperfusion. A small latex balloon was inserted into the left ventricle via the left atrium which allowed to measure the ventricular end-diastolic pressure (diastolic stiffness) and calculate the developed pressure, the maximal rate of pressure generation and maximal rate of pressure decay (+dP/dtmax and -dP/dtmax), the ratio between these two variables (+P/-P), and the time constant of isovolumic relaxation (tau, Tau). The adenosine administered both before the ischemia period, and at the beginning of reperfusion, attenuated the systolic and diastolic stiffness alterations without modifying the isovolumic relaxation. The administration of adenosine did not diminish the CPK and LDH release significantly when it was given before the ischemia period or the beginning of reperfusion.