['To assess complement-mediated myocardial injury on isolated guinea pig working hearts and cardioprotective effects of CD59.', 'Using a modified Langendorff apparatus, isolated guinea-pig working hearts were perfused with a modified Krebs Henseleit buffer containing 3% heat-inactivated human plasma and zymosan (IPZ) (control) (n = 10), 3% normal human plasma and zymosan (NPZ) (n = 10), or 3% normal human plasma and zymosan and 1.5 microg/ml CD59 (NPZC) (n = 10), respectively. Epicardial electrocardiogram (ECG), cardiac output (CO), coronary arterial flow (CF), maximum left ventricular developed pressure (LVP(max)), maximum left ventricular developed pressure increase rate (+ dp/dt(max)), maximum left ventricular developed pressure decrease rate (- dp/dt(max)) and heart rate (HR) were recorded at 0, 15, 30, 45 and 60 min of treatment. After the experiment, immunohistochemical examination was performed to detect the presence of C3a or C5b-9 in the myocardium of the isolated hearts.', 'Compared the IPZ group, hearts treated with NPZ showed a slight depression on ST segments of epicardial ECG at 15 min, a significant elevation between 30 min to 60 min, a decrease in CF, CO, LVP(max), + dp/dt(max) and - dp/dt(max), and an increase in HR at 15 min. The observed alterations in CF, CO, LVP(max), + dp/dt(max) and - dp/dt(max) remained decreased, while the HR remained increased until the end of the protocol. The all above parameters of hearts treated with NPZC were similar to the control group (IPZ) at any given time. Immunohistochemical examination showed positive signals of C3a and C5b-9 in the myocardium of hearts treated with NPZ. C3a was positive in NPZC, and C3a and C5b-9 were negative in IPZ.'] Does cD59 prevent human complement-mediated injuries in isolated guinea pig hearts?