In vitro effects of reactive O2 species on the beta-receptor-adenylyl cyclase system.

The irreversible loss of activity of the sarcolemma-localized beta-receptor-adenylyl cyclase system (beta-RAS) in myocardial ischemia is a well documented phenomenon. Alterations in the sarcolemma (SL) induced by reactive O2 species could be responsible for this loss. Therefore the influence of oxidation of SH-groups and lipid peroxidation induced by Fe2+/Vit. C on the beta-RAS activity was studied. During incubation of SL with Fe2+/Vit. C a transient enhancement followed by a continuous loss of the beta-RAS activity (isoprenaline-, NaF-, Gpp(NH)p-, forskolin-stimulated and basal activity) was observed. In contrast there occurred a continuous loss of SH-groups and lipid peroxidation, beginning immediately after the start of incubation. Loss of SH-groups and lipid peroxidation as well as changes in the beta-RAS did not take place in the presence of the antioxidant t-Butyl-4-hydroxyanisole (BHA) or the Fe(2+)-chelator EGTA. In view of the known ischemia-induced formation of reactive O2 species our results show that these powerful oxidants could contribute to the modulation of the beta-RAS during myocardial ischemia.