Effect of chloro- and bromo-derivatives of isocrotonic acid of bioenergetic processes in Ehrlich ascites cells and isolated mitochondria.

The effect of nine chloro- and bromoderivatives of isocrotonic acid on some bioenergetic processes in both Ehrlich ascites cells and isolated rat liver mitochondria has been investigated. Substances studied in the concentration range 25--200 microM significantly inhibited incorporation of both 14C-adenine and 14C-valine into acid-insoluble material of Ehrlich ascites cells. The rate of 14C-precursors incorporation being directly related to the concentration of the inhibitor. Gamma,gamma-bis-4-ethylphenyl-alpha,beta-dichloroisocrotonic acid fully inhibits both aerobic glucose utilization and lactic acid formation at 200 microM concentration. At lower concentrations, however, glycolysis is stimulated. Maximal stimulation of rat liver mitochondrial respiration in state 4 with succinate as substrate was reached at concentrations as low as 10 microM. On the other hand, these substances were able to release by the oligomycin inhibited respiration of rat liver mitochondria. Our data suggest that cytotoxic and cancerostatic action of isocrotonic acid derivatives lies primarily in the exclusion of key processes in the energy metabolism of Ehrlich ascites cells and isolated mitochondria.