Expression of cardiac troponin T isoforms in skeletal muscle of renal disease patients will not cause false-positive serum results by the second generation cardiac troponin T assay.

The purpose of this study was to determine whether the two monoclonal anti-cardiac troponin T (cTnT) antibodies used in the second generation cTnT assay (capture Ab, M11.7; detection Ab, M7) would detect expression of cTnT isoforms in skeletal muscle from chronic renal disease patients. Skeletal muscle biopsies obtained from 45 chronic renal disease patients (as well as human heart muscles and normal human skeletal muscles) were prepared for Western blot analysis and blotted with the following anti-cTnT antibodies: M 11.7; M7; JS-2, Lakeland Biomedical; 13-11, Duke University) and anti-cTnI antibody JS-1. Using the M11.7 Ab, 20 of 45 renal skeletal muscles demonstrated one to three cTnT isoforms, MW34 39 kDa. These findings were confirmed by both the Lakeland and Duke antibodies. However the BM M7 antibody detected, in two of 45 muscles, only a protein with a MW of approximately 39 kDa. All four antibodies demonstrated equivalence in detection the 39 kDa cTnT isoform expressed in heart muscle. None detected any isoforms in normal skeletal muscle. A single cTnI isoform, MW 25 kDa, was detected by JS-1 only in normal adult myocardium. Based on the antibody configuration of the second generation cTnT assay, we conclude that while cTnT isoforms are expressed in human skeletal muscle obtained from chronic renal disease patients, if released into the circulation, they would not be detected.