The effect of tannic acid on the phosphorylation and ATPase activity of mitochondria from blowfly flight muscle

Abstract

Low concentrations (below 10 −6M) of tannic acid reduced the respiratory control index of blowfly flight muscle mitochondria, apparently reducing the rate of phosphorylation, although ADP:O ratios were normal. At higher concentrations, no stimulation in respiration was found when ADP was added. Respiration uncoupled with DNP was only slightly affected by tannic acid, even at high concentration. However, when DNP is added after tannic acid, its effect is dependent both on the concentration of tannic acid and on the time that elapses before the addition of DNP. Tannic acid also inhibited the mitochondrial ATPase activity, the DNP-stimulated activity being particularly sensitive to low concentrations. Comparisons are made with the action of oligomycin and the results are discussed in relation to the effect of tannic acid on erythrocytes.