| Summary: | Mitochondria1 NADH:ubiquinone oxidoreductase (complex I) carries out a number of
well defined functions required for cell physiology. Deficiencies of complex I lead to
multi-system disorders that include several well-known phenotypes such as type 2
diabetes mellitus, Alzheimer's disease as well as less known phenotypes such as
MELAS, Leigh syndrome and MERRF. It was recently identified that ROS sensitive
proteins known as metallothioneins (MTs), are over-expressed in complex I deficient
cell lines and that these proteins have a protective effect against ROS related
pathologies. It is still not clear if isoform-specific MT expression occurs in this
disease and if it plays a significant role in vivo. This study investigated the expression
of different MT isoforms in rotenone-treated Sprague Dawley rats, an in vivo model
that has been used to study cellular biological responses of mitochondria1 complex I
deficiency.
The hypothesis of this study states that a rotenone-induced complex I deficiency
would lead to an increase of MT mRNA expression in vivo. The specific aim was to
determine the relative mRNA expression levels of the three main MT isoforms in
rotenone-treated rat tissues. Real-time PCR was used to achieve this aim. In this
dissertation the differential expression of MT-1, MT-2 and the brain specific isoform,
MT-3 in brain, liver, heart- and skeletal muscle tissues of rotenone-treated Sprague
Dawley rats is described.
The results indicate that MT-1 expression is significantly increased in the liver as well
as, but to a lesser extent, in the brain and heart muscle. MT-1 expression in skeletal
muscle was not detected. In contrast, significant increases in expression were
observed for MT-2 in all the tissue types with an approximate two-fold increase at the
highest rotenone dosage in liver, brain and heart muscle. Skeletal muscle had the
smallest increase. For MT-3, no detectable levels of expression could be observed in
skeletal and heart muscle. Surprisingly, levels of expression occurred in the liver
which slightly (43%), but significantly increased at the highest rotenone dose. As
expected, much higher relative levels of MT-3 expression were observed in brain
Abstract
tissue with a more pronounced increase (almost two-fold) at the highest rotenone
dose.
As the hypothesis of this study proposed, the in vivo data generated from this study
supports the published in vitro data which showed that a rotenone-induced complex I
deficiency results in MT expression. This over expression may contribute to a
protected effect on the pathology of this disease although this still needs to be
established. Furthermore, the results of this study show that the expression of the
various MT isoforms in rotenone-treated rat tissues is not expressed in a similar way
to the induced deficiency which may point to a differential regulation and response of
the three MT isoforms to such a deficiency. === Thesis (M.Sc. (Biochemistry))--North-West University, Potchefstroom Campus, 2006.
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