Modeling of transendothelial transport

Area of Science:

• Cardiovascular Physiology
• Endothelial Cell Biology
• Solute Transport

Background:

• Capillary-tissue exchange of hydrophilic solutes in the heart primarily occurs via aqueous channels between endothelial cells (ECs).
• Adenosine, a vasoactive agent, undergoes transport across the plasmalemma of ECs in addition to diffusion through clefts.

Purpose of the Study:

• To estimate the conductance of the facilitated transport mechanism for adenosine in the heart.
• To investigate the role of endothelial cells in adenosine exchange and regulation within the cardiac tissue.

Main Methods:

• Utilized the multiple-indicator dilution technique, comparing tracer adenosine flux with a non-transported analog (9-beta-D-arabinofuranosylhypoxanthine).
• Employed a mathematical model simulating exchanges among capillary, EC, interstitium, and myocardial cells.

Main Results:

• The facilitated transport mechanism's conductance, equivalent to a permeability-surface area product, was estimated.
• Analysis indicated high permeability of the abluminal surface of ECs to adenosine.

Conclusions:

• Endothelial cells may constitute a significant component of the system responsible for adenosine exchange in the heart.
• ECs potentially contribute to the regulation of adenosine levels and function within the cardiac microvasculature.