Inhibitory probes of mitochondrial ATPase and the action of DDT

AbstractChemical inhibitors were used as probes of mitochondrial ATPase to determine the site of action of DDT on oligomycin‐sensitive mitochondrial ATPase (OS‐ATPase) using whole mitochondria isolated from red coxal muscle of the American cockroach. Several plotting procedures were employed to delineate the form of inhibition. Relative potency and joint action were used to detect similar action, synergism, and antagonism between DDT and the inhibitory probes DCCD, Nbf‐CI, and oligomycin. DDT demonstrated not (strictly) competitive kinetics and may be acting as an uncompetitive inhibitor. DDT and DCCD produced similar additive action. At limiting concentrations of DCCD, inhibition was reduced in the presence of DDT. Effects shown by oligomycin were not altered by DDT. DDT enhanced the effects of Nbf‐CI. These interactions, together with the demonstration of not (strictly) competitive kinetics, indicate that DDT may be acting on the membrane sector as an allosteric modifier.