Respiratory changes induced by guanidines and cations in submitochondrial particles

Alkylguanidines inhibit the respiration of submitochondrial particles oxidizing NADH, while hydrophilic guanidines stimulate the rate of oxygen uptake. Regardless of the effect that a guanidine exerts on respiration, all guanidines tested inhibited the stimulatory action of K⁺ on the oxygen uptake of submitochondrial particles. It was found also that octylguanidine modified the Arrhenius plot of respiration of the particles. These findings suggest that alkylguanidines exert their action through the interaction of the alkyl chain with a hydrophobic region in the membrane and also through the interaction of the guanidine moiety with a certain locus in the membrane.The results of studies made on the effect of a wide variety of cations on the respiration of submitochondrial particles may be explained on the assumption that in the inner membrane of the mitochondria exists a negatively charged surface or region with which cations can interact. These results also suggest that the stimulation or inhibition of respiration induced by a given cation depends on the ease with which it can move within this hypothetical negative region.