Fast and slow skeletal troponin I in serum from patients with various skeletal muscle disorders: a pilot study.
BACKGROUND
Detection of skeletal muscle injury is hampered by a lack of commercially available assays for serum markers specific for skeletal muscle; serum concentrations of skeletal troponin I (sTnI) could meet this need. Moreover, because sTnI exists in 2 isoforms, slow (ssTnI) and fast (fsTnI), corresponding to slow- and fast-twitch muscles, respectively, it could provide insight into differential injury/recovery of specific fiber types. The purpose of this study was to investigate whether the 2 isoforms of sTnI and their modified forms are present in the blood of patients with various skeletal muscle disorders.


METHODS
Serial serum samples were obtained from 25 patients with various skeletal muscle injuries. Serum proteins were separated by a modified sodium dodecyl sulfate-polyacrylamide gel electrophoresis protocol followed by Western blotting for sTnI with monoclonal antibodies specific to ssTnI and fsTnI.


RESULTS
We observed (a) intact and, in some cases, degraded sTnI products; (b) evidence of posttranslational modifications in addition to proteolysis; and (c) differential detectability of both skeletal isoforms in the same patient.


CONCLUSIONS
It is possible to monitor both sTnI isoforms; this could lead to the development of new diagnostic assays for skeletal muscle damage.
Simpson
Jeremy A
JA
Department of Physiology, Queen's University, Kingston, Ontario, Canada.
Labugger
Ralf
R
Collier
Christine
C
Brison
Robert J
RJ
Iscoe
Steve
S
Van Eyk
Jennifer E
JE
D000911:Antibodies, Monoclonal; D015153:Blotting, Western; D004591:Electrophoresis, Polyacrylamide Gel; D005260:Female; D006801:Humans; D008297:Male; D018656:Muscle Fibers, Fast-Twitch / Q000378:metabolism*; D018657:Muscle Fibers, Slow-Twitch / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000378:metabolism*; D009135:Muscular Diseases / Q000378:metabolism*; D010865:Pilot Projects; D020033:Protein Isoforms / Q000378:metabolism; D019210:Troponin I / Q000097:blood*
D000911:Antibodies, Monoclonal; D020033:Protein Isoforms; D019210:Troponin I