The effect of plant triterpenoid betulin and its derivative betulonic acid on rat mitochondria is considered. It was found that betulonic acid and, to a lesser extent, betulin activate mitochondrial respiration in states 2 and 4 and inhibit respiration stimulated by ADP and DNP. In this case, the effect of betulonic acid leads to a significant decrease in respiratory control and the ADP/O coefficient, as well as to a decrease in membrane potential. The effects of both compounds were most pronounced when succinate was used as a respiratory substrate. It was established that the effect of these agents on the functional parameters of organelles is due to both the protonophore effect of betulonic acid and the inhibition of respiratory chain complexes by both compounds. Both agents also significantly enhanced the generation of H2O2 in succinate oxidizing mitochondria, while betulonic acid exerted an antioxidant effect in the presence of NAD-dependent substrates. It was also found that betulin induces mitochondrial aggregation. Betulonic acid was much less effective in this case. Possible mechanisms of the effect of betulin and betulonic acid on the functioning of rat liver mitochondria are discussed.
betulin, betulonic acid, mitochondria, inhibition, aggregation
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