Neutrophils delay functional recovery of the post-hypoxic heart of the rabbit

A postischemic contractile dysfunction termed myocardial stunning has been described in vivo and is attributed, in part, to the generation of oxygen-derived free radicals and the presence of neutrophils. An analogous contractile derangement occurs in the posthypoxic heart in vitro. This study determined the role of neutrophils in hypoxia/reoxygenation-induced cardiac dysfunction in the isolated buffer-perfused rabbit heart utilizing a recirculating system with or without neutrophils present. In control hearts perfused with a neutrophil-free buffer, reoxygenation after 20 min of hypoxia was associated with a slow recovery of contractility which returned to prehypoxic values by 30 to 45 min. Although perfusion with buffer-containing neutrophils did not affect the hypoxia-induced decrease in myocardial contractility, the recovery of contractile function during subsequent reoxygenation was significantly diminished (P less than .01 vs. control), remaining depressed by 30 to 35% at 45 min. The myocardial neutrophil content increased approximately 2-fold in response to hypoxia and reoxygenation, as assessed using 51Cr-labeled neutrophils. The deleterious effects of neutrophil perfusion on cardiac function could not be attributed to neutrophil-mediated plugging of coronary vessels or enhanced myocellular damage. These results support the concept that neutrophils contribute to the cardiac dysfunction described in this model.