EFFECT OF HYPOXIA AND REOXYGENATION ON THE ISOLATED RABBIT HEART DETERMINED BY MONOCLONAL ANTIMYOSIN ANTIBODY UPTAKE

Objective: The aim was to examine the effect of hypoxia and reoxygenation upon the isolated rabbit heart, and to determine whether or not irreversible tissue injury develops in association with the reintroduction of molecular oxygen to the previously hypoxic heart. Methods: Isolated rabbit hearts suspended on a Langendorff apparatus and perfused with a modified Krebs-Henseleit buffer were subjected to either 5 or 30 min hypoxia and, when applicable, followed by 45 min reoxygenation. The effect of hypoxia and reoxygenation upon the isolated heart was determined with a 125labelled monoclonal antibody to the intracellular protein myosin. Determination of tissue creatine kinase release and morphological analysis, using lanthanum chloride as a marker of vessel damage, were also performed to document the uptake of antimyosin with myocardial tissue injury. Results: Hearts subjected to 30 min hypoxia followed by 45 min reoxygenation showed a significant increase in antimyosin uptake when compared to hearts exposed to 30 min hypoxia. Creatine kinase release and morphological analysis showed an increase in intracellular damage in hearts receiving 30 min hypoxia and 45 min reoxygenation when compared to hearts receiving 30 min hypoxia without subsequent reoxygenation. Hearts subjected to 5 min hypoxia followed by reoxygenation did not show a significant increase in antimyosin uptake as compared to continuously oxygenated control hearts or hearts made hypoxic for 5 min without subsequent reoxygenation. Conclusions: Antimyosin antibody binding increased in hearts subjected to hypoxia and reoxygenation compared to hearts subjected to hypoxia without reoxygenation. The data provide compelling evidence that reoxygenation of hypoxic tissue exacerbates the extension of cellular damage. The ability of superoxide dismutase and catalase to decrease antimyosin uptake suggests that reactive oxygen species play a role in reoxygenation induced myocardial damage. This study also provides evidence that the labelled antimyosin antibody provides a convenient approach to quantitate the extent of damage induced by hypoxia with and without subsequent reoxygenation.