Generation of free radicals in Langendorff and working hearts during normoxia, hypoxia, and reoxygenation.

The release of .OH and alkyl free radicals into the coronary flow were compared in Langendorff perfused and working rat hearts during normoxia (30 min), hypoxia (30 min) and reoxygenation (60 min) by means of spin-trapping techniques using 5,5-dimethyl-1-pyrroline-1-oxide (DMPO). In Langendorff hearts, there was a small but steady increase in the radical concentration during the course of hypoxia and reoxygenation. At the start of reoxygenation, only small initial peaks of hydroxyl and alkyl radicals occurred. After a general decrease of free radical production during hypoxia, working hearts produced nearly double the amount of free radicals during reoxygenation as Langendorff hearts. After an initial large increase during early reoxygenation, the amount of free radicals produced fluctuated on a high level during the remaining reoxygenation period. Heart work is thus correlated with an increased production of free radicals, possibly due to an increase in oxygen consumption by the heart.