Myocardial flavin reductase and riboflavin: a potential role in decreasing reoxygenation injury.

Ferrylmyoglobin has been implicated in cardiac reoxygenation damage. Flavin reductase, an enzyme previously isolated from erythrocytes, can reduce ferrylmyoglobin in the presence of sufficient flavin concentrations. Flavin reductase mRNA signals were detected in rabbit heart, lung, liver, kidney, and isolated cardiomyocytes. It was hypothesized that increasing flavin reductase catalysis by administering flavins exogenously could decrease cardiac reoxygenation damage in isolated rabbit hearts. Riboflavin (150 microM) inhibited reoxygenation-induced lactate dehydrogenase release by 57%, an effect prevented by hematoporphyrin, a flavin reductase inhibitor. The results suggest that riboflavin supplementation has cardioprotective effects during reoxygenation and that these effects are mediated by flavin reductase.