Exogenous adenosine and postischemic dysfunction in the isolated rabbit heart

It is recognized that adenosine lessens the systolic alterations of the pos tischemic ventricular dysfunclion ("stunned myocardium"), but little is kno wn about the drug's effects on the diastolic phase of the cardiac cycle. Th e aim of this work was to determine the effect of adenosine when it was adm inistered: a) before ischemia and during reperfusion, and b) from the early reperfusion period to the end of the experiment on the systolic and diasto lic function of the "stunned myocardium". An additional objective was to de termine whether adenosine modifies the release of creatinphosphokinase (CPK ) and lactatedehydrogenase (LDH), in the "stunned myocardium". Rabbit isola ted isovolumic hearts were perfused according to Langendorff's technique, a nd subjected to 15 minutes global ischemia and 30 minutes reperfusion. A sm all 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 pressu re generation and maximal rate of pressure decay (+dP/dt(max) and -dP/dt(ma x)), the ratio between these two variables (+P/-P), and the time constant o f isovolumic relaxation (tau, Tau). The adenosine administered both before the ischemia period, and at the beginning of reperfusion, attenuated the sy stolic and diastolic stiffness alterations without modifying the isovolumic relaxation. The administration of adenosine did not diminish the CPK and L DH release significantly when it was given before the ischemia period or th e beginning of reperfusion.