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In vitro generation of thiobarbituric acid reactive
substances (TBARS) is frequently used to assess organ susceptibility to
lipid peroxidation. The yield of TBARS is severalfold enhanced by an
addition of iron ions with reductors or chelators such as ascorbate,
NADPH, ADP or pyrophosphate. The process cannot be interpreted in a
simple way, since it involves several enzymatic and nonenzymatic
reactions. There are no clear interpretations of the ambiguous effects
of denaturating factors and chelating agents on TBARS generation. Also
controversy arises from the curvilinear relationship between the
homogenate concentration and the yield of TBARS. This has been modelled
in the present work by combining two functions describing the sequential
reaction with two limiting steps. One of them is related to catalytic
action of iron and ascorbate, while the other to an enzyme, possibly
phospholipase A2, as has been suggested by some investigators. Two
models should be considered since it is impossible to decide which
kinetic equation should predominate in the model. Nevertheless, the
model reflects kinetic properties of the process. The effects of
catalyst concentration and some other modification upon the yield of
TBARS were also investigated experimentally. The results of experiments
and modelling showed that the analytical procedures used by
investigators need standardisation as the results obtained under a
variety of procedures may reflect quite different properties of the
living systems.
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