Key Points
- This research investigates how titin-based passive force affects calcium sensitivity and tension generation in cardiac myocytes.
- Measured force-pCa relations at varying sarcomere lengths (2.0 and 2.3 microm) with adjusted passive tension levels.
- Utilized small-angle x-ray diffraction to evaluate interfilament lattice spacing in mouse left ventricular muscle.
- Manipulated passive tension and analyzed its effects on myocyte dimensions and activation characteristics.
- At 2.3 microm SL, low passive tension resulted in a 0.09±0.02 shift in pCa(50), while high passive tension increased the shift to 0.25±0.03 pCa units.
- Passive tension increased pCa(50) with reduced interfilament spacing achieved through dextran.
- Cell width and interfilament spacing decreased inversely with increasing passive tension, indicating titin's modulation role.
Structured PICO
PPopulationMouse skinned cardiac myocytes and mouse left ventricular wall muscle
IInterventionVariation of passive tension at 2.3 microm sarcomere length (from ~1 to ~10 mN/mm2) and reduced interfilament lattice spacing with dextran
CComparatorSarcomere length of 2.0 microm and low passive tension
OOutcomeForce-pCa relations (calcium sensitivity of active tension, pCa50)surrogate
Titin-based passive tension modulates calcium sensitivity of active tension in cardiac myocytes by altering interfilament lattice spacing, suggesting a role for titin in systolic force generation.