Fatty acid transfer across the myocardial capillary wall

Area of Science:

• Cardiovascular Physiology
• Metabolic Biochemistry
• Endothelial Transport

Background:

• Fatty acids (FA) are crucial energy substrates for the heart.
• Understanding transcapillary FA movement is vital for cardiac metabolism and function.
• The role of capillary wall permeability versus protein binding in FA transfer remains debated.

Purpose of the Study:

• To investigate the mechanisms of fatty acid (FA) release and transfer across the cardiac capillary wall.
• To determine the factors influencing interstitial FA concentration and uptake rates.
• To elucidate the role of protein binding and dissociation rates in transcapillary FA transport.

Main Methods:

• Analysis of interstitial transudate from isolated, isometrically working, perfused rat hearts.
• Manipulation of medium FA concentrations and FA/albumin ratios.
• Calculation of diffusion rates, permeability surface-area values, and dissociation-rate constants.

Main Results:

• Lowering medium FA concentration significantly decreased interstitial FA concentration and uptake rates.
• Transcapillary diffusion resistance was not the primary limiting factor for FA transfer.
• FA transfer occurs predominantly bound to carrier proteins, with dissociation rates limiting transcapillary gradients.

Conclusions:

• Cardiac capillary walls present minimal diffusion barrier for fatty acids.
• Transcapillary fatty acid gradients are primarily dictated by the limited dissociation rate of FA-albumin complexes.
• Fatty acid transport across the cardiac endothelium is predominantly mediated by protein carriers.