Myoglobin function evaluated in working heart tissue

Area of Science:

• Physiology
• Biophysics
• Computational Biology

Background:

• Myoglobin's role in oxygen transport is debated, especially in working heart muscle.
• Previous models using literature values for myoglobin diffusion showed minimal facilitation.
• Muscle contraction may influence oxygen diffusion, potentially augmenting myoglobin's role.

Purpose of the Study:

• To investigate elevated diffusion coefficients for oxygen and myoglobin in working heart tissue.
• To model oxygen transport using the Radially-Averaged, Axially-Distributed (RAAD) model.
• To determine if myoglobin significantly facilitates oxygen diffusion in the heart.

Main Methods:

• Utilized the RAAD model, incorporating axial diffusion, myoglobin facilitation, and Michaelis-Menten oxygen consumption.
• Employed a variable-mesh finite-difference scheme for numerical solutions.
• Optimized model parameters using a Nelder-Mead simplex routine to minimize error between predicted and experimental pO2 data.

Main Results:

• Myoglobin facilitation had minimal impact on predicted oxygen distribution.
• Optimized oxygen diffusion coefficients remained elevated.
• Optimized myoglobin diffusion coefficients were lower than experimentally measured values.

Conclusions:

• Myoglobin does not significantly facilitate oxygen diffusion to tissue in the steady state.
• Myoglobin diffusion is not elevated in working heart tissue.
• Contractile mechanisms do not appear to augment myoglobin-facilitated oxygen transport in this model.