BY: Francisco Peixoto, Joaquim A. F. Vicente and
Vítor M. C. Madeira
The effects of dicamba, a widely used broad-leaf herbicide, on rat liver
mitochondrial bioenergetic activities were examined. The results obtained for
state 4 respiration indicate not only an uncoupling effect, the result of an
increase on the permeability of inner mitochondria membrane to protons, but also
a strong inhibitory effect on the redox complexes. State 3 and respiration
uncoupled by FCCP (carbonylcyanide p-trifluoromethoxyphenylhydrazone) were
inhibited to approximately the same extent, i.e. by about 70%. Depression of
respiratory activity is essentially mediated through partial inhibition of
mitochondrial complexes II and III. ATPase activity was much less depressed by
dicamba than ATP synthase activity. Therefore, a considerable part of the
inhibition observed on ATP synthase is the result of an inhibition on the redox
complexes. The loss of phosphorylation capacity, induced by dicamba, was
in the last analysis not only the result of a direct effect of 
dicamba on the enzymatic complex (F 0–F 1 ATPase) but also the
result of a deleterious effect on the integrity of the mitochondrial membrane,
which can promote an inhibition of the respiratory complexes and an increase of
the proton permeability of the inner membrane.Yangzhou pioneer chemical CO.,LTD
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