EFFECT OF ENALAPRILAT ON POSTISCHEMIC SYS TOLIC AND DIASTOLIC DYSFUNCTION (STUNNED MYOCARDIUM) ON THE ISOLATED RABBIT HEART

The aim was to determine: 1) whether Enalaprilat (0.08 mg/kg/min) admi nistration: a) before ischemia or b) at the beginning of reperfusion i mproved the postischemic systolic and diastolic dysfunction (''stunned myocardium'') and attenuated the ''hyperfunction'' phase at the begin ning of reperfusion; and 2) whether creatine kinase (CPK), and lactate dehydrogenase (LDH) activities, and lactate release are involved in t he protective effects of Enalaprilato. An isolated isovolumic rabbit h eart preparation was used as experimental model and subjected to 15 mi nutes of ischemia followed by 30 minutes of reperfusion, without (grou p 1), and with Enalaprilat before the ischemia (group 2) and at the be ginning of reperfusion (group 3). Left ventricular developed pressure, and end diastolic pressure (diastolic stiffness) were measured and th e time constant of isovolumic relaxation (t, Tau) and the ratio betwee n + dP/dt(max) and -dP/dt(max) were calculated. For the determinations of lactate release and CPK and LDH activities in the perfusate, sampl es were taken from the coronary effluent for spectrophotometrical meas urements. In comparison to the stunned group (group 1) both Enalaprila t preischemia (group 2) and postischemia (group 3) exerted a significa nt protective effect on the postischemic recovery of contractile state and diastolic stiffness, and attenuated the ''hypercontractile'' phas e in both groups. However Enalaprilat failed to improve myocardial rel axation. Lactate release was also attenuated, but the enzyme activitie s were not modified.