6533b7d8fe1ef96bd1269996

RESEARCH PRODUCT

Effects of the herbicides Benzoylpropethyl and flampropisopropyl on rat liver mitochondria : an alteration in membrane fluidity ?

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Abstract The action of the herbicides benzoylpropethyl and flampropisopropyl, and the corresponding unesterified acids was studied in rat liver mitochondria. The herbicides were found to (a) inhibit the mitochondrial electron transfer in complex III or at the level of ubiquinone (I50 of 4 nmol mg protein−1 for flampropisopropyl and 18 for benzoylpropethyl with succinate as a substrate); (b) have an additional (however less sensitive) site of inhibition near succinate dehydrogenase; and (c) interfere with energy transfer. Sensitivity was increased 2- (benzoylpropethyl) and 3.5-fold (flampropisopropyl) as the rats age increased from 12–13 weeks to 23–26 weeks. The free acids were far less effective. Since the herbicides benzoylpropethyl and flampropisopropyl are readily hydrolyzed by animals and since the free acids are less effective than the herbicides, it explains why these potentially harmful compounds have a low acute toxicity. Swelling studies in isoosmotic salts suggested that the two herbicides decrease membrane fluidity, an action which was assumed to be responsible for the electron transfer inhibition and, via inhibition of phosphate transport, the interference with energy transfer.