Pore-like diffusion barriers in murine cardiac myocytes

Area of Science:

• Cellular Biophysics
• Molecular Transport
• Cardiac Physiology

Background:

• Understanding solute diffusion within cardiac myocytes is crucial for comprehending cellular function and drug delivery.
• Cytoplasmic environment presents complex barriers to molecular movement, influenced by protein networks and organelle structures.

Approach:

• Employed optical and electrical methods to measure diffusion of various molecular weights in BL6 murine cardiac myocytes.
• Investigated the roles of myofilaments, mitochondria (Vdac1), and sarcolemma in diffusion restriction.
• Compared diffusion in intact myocytes, permeabilized myocytes, and isolated myofilaments.

Key Points:

• Solute diffusion is significantly restricted (>30-fold) with increasing molecular weight, consistent with pore-like structures.
• ATP diffusion is 8-10 times slower in cardiac cytoplasm compared to free water.
• Both myofilaments and mitochondria networks demonstrably restrict solute diffusion in cardiac myocytes.

Conclusions:

• Cardiac myofilaments and mitochondrial networks act as significant barriers to solute diffusion.
• Long-range solute transport may be facilitated by passage through porin channels and intramitochondrial spaces.
• Diffusion restriction is strain-dependent and influenced by specific mitochondrial proteins like Vdac1.