[Curve-fit with hybrid logistic function for intracellular calcium transient]

Area of Science:

• Cardiovascular Physiology
• Biophysics
• Computational Biology

Context:

• Cardiac function involves complex contraction and relaxation processes.
• Intracellular calcium (Ca2+) dynamics are critical regulators of myocardial contraction and relaxation.
• Previous models struggled to accurately represent these dynamic processes.

Purpose:

• To introduce and evaluate the hybrid logistic (HL) function for curve-fitting cardiac physiological data.
• To compare the efficacy of the HL function against conventional mathematical models.
• To propose a novel framework for analyzing calcium transients (CaT) and related molecular events.

Summary:

• The hybrid logistic (HL) function, a novel mathematical model, demonstrates superior curve-fitting capabilities for isovolumetric left ventricular (LV) pressure and isometric twitch tension curves compared to polynomial, exponential, and sinusoidal functions.
• The HL function also provides a better fit for intracellular Ca2+ transient (CaT) curves, measured using aequorin, in isolated cardiac muscle preparations.
• The two components of the HL function are hypothesized to represent distinct phases of Ca2+ handling, cross-bridge cycling, and associated molecular interactions during myocardial contraction and relaxation.

Impact:

• This HL modeling approach offers a more accurate representation of cardiac mechanical and Ca2+ dynamics.
• It provides a potentially more powerful tool for investigating Ca2+ handling, Ca2+-TnC interactions, and cross-bridge cycling.
• The findings could lead to improved understanding and modeling of cardiac electro-mechanical coupling and dysfunction.