Analysis of microvascular permeability to macromolecules by video-image digital processing

Area of Science:

• Physiology
• Microcirculation Research
• Transport Phenomena

Background:

• Understanding macromolecular transport across microvascular walls is crucial for various physiological and pathological processes.
• Previous studies often used whole organ techniques, potentially obscuring micro-level transport dynamics.

Purpose of the Study:

• To quantitatively assess macromolecular transport dynamics across microvascular walls in vivo.
• To determine the effective microvascular permeability (P) for different sized macromolecules.
• To investigate the influence of interstitial space on macromolecular permeation.

Main Methods:

• Intravital fluorescence microscopy in hamster cheek pouch.
• Utilized fluorescein isothiocyanate-labeled dextrans (FITC-Dx) of varying molecular weights (20,000-70,000 MW) as tracers.
• Employed digital video-image processing and a one-dimensional two-compartmental diffusion model with nonlinear regression to quantify permeability.

Main Results:

• Effective microvascular permeability (P) was determined for FITC-Dx 20, 40, and 70.
• Calculated P values (x 10^-8 cm/sec) were 47.8 ± 8.7 (20 kDa), 31.7 ± 5.9 (40 kDa), and 17.5 ± 4.1 (70 kDa).
• Permeability decreased significantly with increasing dextran size, indicating size-dependent transport.

Conclusions:

• The study provides quantitative in vivo measurements of macromolecular transport across microvessels.
• Interstitial resistance plays a significant role in modulating macromolecular permeation, explaining differences from whole organ studies.
• Findings contribute to a better understanding of microvascular barrier function and macromolecular dynamics.