2-Mercaptopropionylglycine improves aortic flow after reoxygenation in working rat hearts.

The cardioprotective concentration range of the thiol drug 2-mercaptopropionylglycine (MPG) was investigated during reoxygenation after 30 min of hypoxia. It was found that aortic flow and frequency were increased by 1 mM MPG. Coronary flow, systolic and diastolic pressure were not significantly influenced by the drug. Mitochondria, isolated from hearts after termination of the perfusion phases, revealed increased values of RCI, when MPG had been present in the previous reoxygenation phase at 1 mM concentration. 5 mM MPG no longer showed a protective influence on the above cardiac and mitochondrial parameters. ATPase activities were decreased at 1 mM MPG by 14% and at 5 mM MPG by 40% of the controls. The latter concentration of MPG also doubled the inhibitory action of carboxyatractyloside on ATPase activity, indicating a structural change of the adenine nucleotide carrier. 1 mM MPG is considered an optimal therapeutic range in this model. The mechanism of action most probably includes an SH/-S-S-interchange reaction as well as a free radical scavenging mechanism. For many thiols, the latter is known to occur in the presence of metal ions.