Key Points
- To determine how troponin isoform alterations affect contractile regulation across human fetal, normal adult, and failing adult myocardium.
- Isolated cardiac troponin and tropomyosin from human fetal, normal adult, and failing adult hearts.
- Characterized troponin subunit and isoform expression via SDS-PAGE and immunoblotting.
- Quantified regulatory function by tracking actin-tropomyosin filament sliding over immobilised heavy meromyosin at pCa 9 and pCa 5.
- At relaxing calcium levels (pCa 9), troponin from fetal and adult hearts reduced the moving filament fraction from 90% to less than 15% with a 25% to 30% decrease in velocity.
- At activating calcium levels (pCa 5), normal adult troponin increased filament velocity by 47 ± 3%, whereas fetal troponin increased velocity by 4 ± 6% and failing adult troponin showed an intermediate increase of 31 ± 5%.
- Fetal myocardium displayed distinct troponin I and troponin T isoform expression compared with adult tissue, whereas no isoform expression differences emerged between normal and failing adult hearts.
Structured PICO
PPopulationHuman cardiac troponin isolated from foetal, normal adult, and failing adult hearts
IInterventionFunctional analysis using in vitro motility assay and protein content analysis by SDS PAGE and immunoblotting
CComparatorComparison among foetal, normal adult, and failing adult troponin
OOutcomeRegulatory function (fraction of filaments moving and filament velocity) and troponin isoform expressionsurrogate
The regulatory function of troponin from adults with end-stage heart failure differs from normal adult troponin, suggesting a role for altered troponin function in heart failure pathophysiology.