The expression of P-selectin on postischemic endothelium after reperfusion has been shown to trigger neutrophil attachment and the subsequent inflammatory responses. Extensive studies have demonstrated that P-selectin is involved in the progression of neutrophil-mediated myocardial infarction and no-reflow phenomenon. In the present study, we examined the effects of selectin inhibitors, sialyl Lewis X-oligosaccharide and anti-P-selectin monoclonal antibody, PB1.3 on neutrophil-dependent left ventricular dysfunction in isolated rat heart. The hearts were subjected to global ischemia for 20 min and then reperfused for 45 min with rat plasma in the presence of human neutrophils during the first 5 min of the reperfusion. Left ventricular developed pressure and other parameters of the left ventricular function deteriorated throughout the reperfusion period in a neutrophil-dependent manner. In contrast, the coronary flow was reduced early on (< 15 min) but recovered to the level in the hearts reperfused with no neutrophils 45 min after the reperfusion. We examined the effects of selectin inhibitors under experimental conditions in which the hearts were perfused with 30 million neutrophils. The treatment with sialyl Lewis X-oligosaccharide at a dose of 0.3 mg/min resulted in amelioration of left ventricular developed pressure to 57.2 +/- 14%, compared to 26.1 +/- 4.3% in the saline-treated group (P < 0.05). Similarly, the treatment with mouse anti-human P-selectin monoclonal antibody (IgG1) PB1.3 at a dose of 0.6 mg/min resulted in the prominent recovery of left ventricular developed pressure after 45 min of reperfusion (59.9 +/- 9.3% vs. 26.1 +/- 4.3% in the saline-treated group, P < 0.05). PB1.3 also attenuated the elevation of left ventricular end-diastolic pressure compared to that of the saline-treated group during the reperfusion period. Moreover, the treatment with PB1.3 ameliorated the recovery of coronary flow until 10 min after the reperfusion and the recovery of coronary flow 10 min after the reperfusion was 55.2 +/- 9.2%, as compared to 28.2 +/- 7.7% in saline-treated hearts (P < 0.05). To our knowledge, this is the first direct demonstration that the specific inhibition of P-selectin results in the inhibition of neutrophil-mediated left ventricular dysfunction or myocardial stunning.