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Polarographic Evaluation of
Mitochondrial Enzymes Activity in Isolated Mitochondria and in
Permeabilized Human Muscle Cells with Inherited Mitochondrial
Defects
L. WENCHICH, Z. DRAHOTA1, T. HONZÍK, H. HANSÍKOVÁ, M. TESAŘOVÁ,
J. ZEMAN, J. HOUŠTĚK1
Center for Integrated Genomics, Department of
Pediatrics, Charles University and 1Institute of
Physiology, Academy of Sciences of the Czech Republic, Prague,
Czech Republic
Received September 20, 2002
Accepted November 29, 2002
Summary
Inherited disturbances of the mitochondrial energy generating system represent a
heterogeneous group of disorders associated with a broad spectrum of metabolic
abnormalities and clinical symptoms. We used the polarographic and
spectrophotometric method for detection of mitochondrial disorders, because
these two techniques provide a different insight into mitochondrial function. In
six patients suspected of mitochondrial disease we found defects of complex I
(two patients), complex III (one patient), complex IV (two patients) and a
combination of defect of complex III and IV (one patient). Citrate synthase
activity, used as the reference enzyme, was not changed. A comparison of the two
methods showed several differences in evaluation of mitochondrial enzymes
activity due to the fact that both methods used different conditions for enzyme
activity measurements. In contrast to oxygen consumption measurements, where the
function of the whole-integrated respiratory chain is characterized,
spectrophotometric measurements characterize activities of isolated complexes in
disintegrated membranes. However, it may be concluded from our experiments that
both methods provide useful and complementary data about mitochondrial energetic
functions. Whereas spectrophotometric data are suitable for evaluation of
maximal enzyme activities of mitochondrial enzyme complexes, polarographic data
provide better information about enzyme activities in cells with mitochondrial
defects under in situ conditions.
Key words
Mitochondria • Muscle cells • Respiratory chain complexes •
Polarography • Spectrophotometry
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