The myocardial interstitium: its structure and its role in ionic exchange

Area of Science:

• Cardiovascular Biology
• Connective Tissue Research
• Cellular Ultrastructure

Background:

• The myocardial interstitium's structure and composition are crucial for cardiac function.
• Previous studies have not fully defined the rabbit myocardial interstitium's components and spatial organization.

Purpose of the Study:

• To define and quantify the structural components of the rabbit myocardial interstitium.
• To investigate the role of extracellular matrix components, particularly negatively charged substances, in interstitial space.

Main Methods:

• Stereological methods were employed for quantitative analysis of interstitial structures.
• Extracellular space was measured using neutral (carbon-14 sucrose), anionic (sulfur-35 sulfate), and cationic (lanthanum-140) markers.
• The effect of cetylpyridinium chloride on ground substance and lanthanum space was assessed.

Main Results:

• The extracellular space comprises 23% ground substance, 59% blood vessels, 4% collagen, and 7% connective tissue cells.
• Lanthanum (La+++) space significantly differed from sucrose and sulfate spaces, indicating binding to polyanionic structures.
• Cetylpyridinium chloride precipitated ground substance, reducing La+++ space.

Conclusions:

• The rabbit myocardial interstitium exhibits significant structural complexity, characterized by abundant negatively charged ground substance.
• The negatively charged polysaccharides play a key role in cation binding and influence the interstitial space.
• These findings have implications for understanding cation exchange and fluid dynamics in arterially perfused cardiac tissue.