The antifertility agent, gossypol, changes several mitochondrial functions in the presence of Mg2+

1. The effect of gossypol in the presence of K+ or Mg2+, or both, was studied on ATPase activity and respiration of rat liver mitochondria. 2. Respiration was uncoupled in the presence of gossypol, Mg2+, and K+, whereas in the presence of gossypol and Mg2+ a partial inhibition was observed. 3. Gossypol stimulated ATPase activity in the presence of K+ or Mg2+, but maximal activity was observed when both cations were in the incubation medium. 4. Stimulation of ATPase activity in the presence of Mg2+ was dose related. 5. EDTA reverted the stimulation produced by gossypol on ATPase activity. 6. Gossypol had no effect on the ATPase activity of submitochondrial particles, which suggests an indirect action of gossypol on the enzyme. 7. Mitochondrial membrane potential showed a higher collapse in the presence of gossypol and 1 mM MgCl2. 8. The observed effects of gossypol could be explained by the collapse of the mitochondrial membrane potential.