Studies on the mechanism of action of salicylate: effects on orthophosphate-exchange reactions associated with oxidative phosphorylation

Abstract

The action of salicylate on various reactions associated with the oxidative phosphorylation system of the respiratory chain of mitochondria has been investigated. The reactions studied were: (a) the [32P]P1-ATP exchange reaction, (b) the P1-H218O exchange, and (c) ATPase activity.Addition of salicylate to mitochondrial suspensions resulted in inhibition of both exchange reactions accompanied by a stimulation of ATPase. 2,4-Dinitrophenol had a qualitatively similar action but on a quantitative basis was found to be approx. 100 times as potent as salicylate with regard to inhibition of exchange reactions, and at a given level of inhibition of the [32P]P1-ATP exchange reaction resulted in greater stimulation of ATPase activity.The effects of other compounds chemically or pharmacologically similar to salicylate were investigated. None of the compounds approached salicylate or 2,4-dinitrophenol in their ability to depress [32P]P1-ATP exchange or stimulate ATPas activity.Under appropriate conditions human erythrocyte hemolysates or the 105400 × g supernatant fraction of rat-liver homogenates were found to catalyze a [32P]P1-ATP exchange reaction. These exchange reactions were found to be insensitive to salicylate or 2,4-dinitrophenol.