Cardiac troponin T and creatine kinase MB are not increased in exterior oblique muscle of patients with renal failure

Background: Serum cardiac troponin T (cTnT) concentrations may be increased in patients with renal dysfunction without evidence of cardiac damage, as assessed by conventional methods. It has been suggested that these positive measurements result from the expression in skeletal muscle of fetal isofor ms of cTnT, which are detected by the cTnT immunoassay. Methods: Skeletal muscle (exterior oblique) biopsies were taken from health y living kidney donors (n = 5) and transplant recipients (n = 19). The amou nts of cTnT and creatine kinase (CK) isoenzymes in skeletal muscle of healt hy controls were compared with those in patients with renal failure (Wilcox on-Mann-Whitney test). cTnT was measured quantitatively by a second-generat ion assay, with a limit of detection of 1 mug/g of protein, and qualitative ly by immunohistochemistry and immunoblotting. CK MB was measured by quanti tative electrophoresis. Results: Minute quantities of cTnT were detected in 2 of the 5 (40%) contro l samples and 9 of the 19 (47%) renal failure samples, respectively, at mea n concentrations of <5 mug/g of protein for both subject groups. This was < 1/6000th that found in heart muscle. There was no significant difference in cTnT or CK-MB content in skeletal muscle between healthy controls and pati ents with renal failure. Increased serum cTnT did not predict detectable cT nT in skeletal muscle. cTnT was not detected qualitatively by immunoblottin g or immunohistochemistry in any skeletal muscle samples. Conclusions: Uremia does not affect the content of cTnT or CK-MB in exterio r oblique muscle, suggesting that cTnT detected in serum from patients with renal failure does not originate from skeletal muscle. (C) 2001 American A ssociation for Clinical Chemistry.