Electrochemiluminescent immunoassay for rat skeletal troponin I (Tnni2) in serum.

INTRODUCTION: The identification of xenobiotic-induced skeletal muscle toxicities through the detection of biomarkers in nonclinical studies can be useful early in the drug discovery process to aid in candidate drug decisions. Skeletal muscle troponin I (sTnI) has been identified as a potential marker of skeletal muscle injury in humans and animals. When skeletal muscle tissue is injured, sTnI is released into circulation.

METHODS: Due to the nature of the troponin subunits to form intermolecular complexes and to oxidize under various environmental conditions, the optimal assay required the use of a combination of chelating and reducing agents in the sample preparation. It also required the selection of capture and detection antibodies with specificity to the reduced sTnI monomeric subunit and includes a capture antibody specific for sTnI Type 2 (Tnni2), which is associated with Type 2 "fast twitch" muscle fibers.

RESULTS: We have developed a sensitive and specific assay to detect the concentration of rat sTnI in serum using an electrochemiluminescent (ECL) immunoassay platform with a sensitivity of 2.4 ng/ml and with minimal cross-reactivity with rat cardiac TnI (Tnni3).

DISCUSSION: The use of additives and the wide dynamic range of the ECL platform resulted in an accurate and consistent ECL immunoassay that was able to specifically detect sTnI (Tnni2) in rat serum. This method can be applied to safety assessment in early drug development.