Osmotic reflection coefficient for total plasma protein in lung microvessels.

Area of Science:

• Physiology
• Pulmonary Medicine
• Biophysics

Background:

• The integrity of the microvasculature is crucial for maintaining fluid balance.
• Plasma proteins contribute significantly to oncotic pressure, influencing fluid shifts across capillaries.

Purpose of the Study:

• To estimate the osmotic reflection coefficient (sigma) for total plasma proteins in isolated blood-perfused canine lungs.
• To compare the determined sigma value with those obtained through other methods and in different tissues.

Main Methods:

• Isolated blood-perfused canine lung preparation.
• Measurement of capillary filtration coefficient (Kf,C) using hydrostatic pressures and weight gain.
• Determination of isogravimetric capillary pressure (Pc,i).
• Manipulation of perfusate colloid osmotic pressure (delta IIP) and measurement of subsequent weight changes (delta W/delta t)0 to calculate sigma.

Main Results:

• The average Kf,C was 0.19 +/- 0.05 ml x min-1 x 100g-1 x cmH2O-1.
• The average isogravimetric capillary pressure (Pc,i) was 9.9 +/- 0.5 cmH2O.
• The estimated osmotic reflection coefficient (sigma) for total plasma proteins averaged 0.65 +/- 0.06.

Conclusions:

• The osmotic reflection coefficient for canine lung total plasma proteins is approximately 0.65.
• This value is comparable to estimates from lymphatic protein flux analyses in dog lungs.
• The sigma value for canine lungs is lower than that reported for skeletal muscle using similar methodologies.