Background: Qualitative and quantitative measures of cardiac troponin I
(cTnI) in striated muscle have been reported as part of diverse investigations.
However, there is disparity in the literature regarding the findings of these
analyses. The cTnI molecule can exist in phosphorylated, non-phosphorylated, reduced,
non-reduced, complexed or non-complexed forms. Each of these forms can change the
antigenicity of cTnI, resulting in different antibody-antigen interactions in
different experimental formats, thereby giving rise to the disparities in the
literature.
Methods: cTnI in heart and skeletal muscles were investigated by three
techniques employing the same specific cTnI antibodies: the recently revised
Dade-Behring Dimension RXL assay, immunoblotting and immunohistochemistry.
Results: cTnI was detected in heart muscle but not skeletal muscle using
the quantitative assay and immunoblotting. Unexpectedly, using the same antibodies,
cTnI was not immunolocalized to either heart or skeletal muscle.
Conclusion: The antibody-cTnI interaction might be impeded on fixed
immunohistochemistry sections. Our findings reflect those of a previous study,
showing that cTnI was not detected in skeletal muscle extracts using a quantitative
assay. The behaviour of cTnI antibodies varies depending on experimental design.
Conclusions drawn from experiments using qualitative methods cannot necessarily be
extrapolated to the quantitative assay and vice versa.
