Respiratory and Associated Responses of Carrot Disc to Substituted Phenols.

Abstract

The effects of a series of chloro-, nitro- and bromo-substituted phenols on O2-uptake, glucose-C14 uptake and C14O2 production by carrot discs have been determined. The relative effectiveness of the various phenols in inducing respiratory stimulations was paralleled by their ability to inhibit the uptake of glucose. Concentrations of phenols inhibiting glucose uptake by 50% induced stimulations in O2-uptake. Although the total CO2 output was not curtailed by the treatments, the production of C14O2 was drastically inhibited. However this inhibition was clearly ascribable to the inhibition of glucose uptake, and not to a change in respiratory substrate due to the phenols. Experiments with isolated castor bean mitochondria showed that each of the phenols was able to stimulate O2-uptake, and this is considered to be an uncoupling effect under the experimental conditions. The relative effectiveness of the various phenols in this respect was similar to that in stimulating O2-uptake and depressing glucose uptake in carrot discs. It is concluded that all of the substituted phenols were acting, with different degrees of efficiency, as uncoupling agents.