Ultrasensitive Cross-species Measurement of Cardiac Troponin-I Using the Erenna Immunoassay System

Abstract

Serum cardiac troponin-I (cTnI) has been validated as a biomarker for cardiotoxicity in numerous animal models; however, owing to sensitivity issues cTnI concentrations in healthy, resting animals used in toxicology studies have not been established. Serum from healthy and isoproterenol hydrochloride (iso)-treated rats, dogs, and monkeys were assayed using the Erenna system. The Erenna cTnI assay provided sensitivity < 1 ng/L across human, rat, dog, and monkey cTnI. Linear responses (R 2 = 0.99) were observed for all species. Precision studies yielded interassay CVs of curve fit quantification from 2% to 4% between 1.6 and 5000 ng/L, and 23% at 0.78 ng/L. Strong correlation (R 2 = 0.99) was obtained between Erenna and Beckman Access cTnI. Concentrations of cTnI in healthy animals ranged from 1 to 9 ng/L. In longitudinal studies of iso-treated animals, the concentrations of cTnI in the control vehicle-treated groups were 10-20 ng/L for rats (N = 10) and predose values of 2-3 ng/L for dogs (N = 3). Measured with the Erenna assay system, cTnI was quantifiable at all time intervals tested in all animals treated with iso. The Erenna system provides sensitive measurement of cTnI in rats, dogs, and monkeys, makes it possible to determine small changes from normal concentrations, and provides cTnI values from small volumes of serum.

Longitudinal Studies of Cardiac Troponin-I Concentrations in Serum from Male Sprague Dawley Rats: Baseline Reference Ranges and Effects of Handling and Placebo Dosing on Biological Variability

“…Second, the ULoQ should be adequate to quantify large relative increases of cTnI concentration above baseline in studies of cardiotoxic compounds in rats. For example, cTnI concentrations in rats have been reported to be well over 1000 pg/mL following administration of isoproterenol at doses 0.5 mg/kg (Mitra et al 2008;Schultze et al 2008;York et al 2007), which is significantly greater than a fivefold change from our observed reference range. Thus, to provide maximum coverage of all possible and expected cTnI concentrations, such longitudinal studies require a sensitive immunoassay (LLoQ of at least 3 pg/mL) coupled with a wide dynamic range of over four logs.…”

“…All sera and calibrators were tested in duplicate and the results are presented as the mean of the two measurements. The human National Institute for Standards and Technology standard was used as the standard reference for calibration, which has been shown previously to provide accurate determinations of cTnI concentration in rat serum with this assay (Schultze et al 2008). …”

Comparison of Cardiac Troponin I and T, Including the Evaluation of an Ultrasensitive Assay, as Indicators of Doxorubicin-induced Cardiotoxicity

“…While our assessment of the research assay was limited and the samples were over 2 years old, the precision of the assay was notably not as high as has been reported for rat serum with another high-sensitivity cTnI assay (Schultze et al 2008). Overall, it has been shown that cTnT is stable frozen for a least a year with a minimal decrease (7%) after 2 years of storage (Basit et al 2007).…”

Effect of general anesthesia on plasma cardiac troponin I concentrations in healthy horses

“…cTnI concentrations in healthy human individuals, rats, dogs and monkeys are in the picomolar range, well below the analytical sensitivity of commercially available assays. 22,23 It is highly probable that healthy horses have similar plasma cTnI concentrations and assay sensitivity limitations are the likely reason for failure to detect cTnI in many horses. In addition to undetectable cTnI concentrations pre-anesthesia, most horses of this study did not develop detectable cTnI following anesthesia.…”