[The role of beta-endorphin and pain perception in silent myocardial ischemia]

Plasma beta-endorphin (beta-END) levels were measured before, after exercise tests and at the onset of spontaneous angina in 23 anginal patients (group 1), 23 patients with silent myocardial ischemia (group 2) and 15 healthy volunteers (group 3). The pain perception in three groups was also measured. Before and after exercise, the concentration of beta-END in group 1 was significantly lower than that in group 2 and group 3. The concentration of beta-END during onset of spontaneous angina was also lower than that of angina-free period in group 1. There was no significant difference of beta-END between group 2 and 3. The values of the pain threshold and tolerance in group 1 were lower than those of group 2 and 3. These data suggested that plasma levels of beta-END may be related to occurrence of angina. The anginal patients had a hypersensitivity and hypotolerance for pain. A positive correlation was found between plasma beta-END and pain threshold, the levels of beta-END might affect the pain perception during the onset of myocardial ischemia.