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Microvascular albumin permeability in isolated perfused lung: effects of EDTA
Abstract:
We examined the effects of decreases in perfusate concentrations of calcium and magnesium on the pulmonary vascular permeability in the isolated perfused rabbit lung. The albumin permeability-surface area product (PS) and the albumin reflection coefficient (sigma) were determined in the same lung using 125I- and 131I-labeled albumin tracers. Decreases in vascular Ca2+ and Mg2+ concentrations were induced by adding ethylenediaminetetraacetic acid (EDTA) to the perfusate. Decreases in the concentration of these cations resulted in an increase in the PS from a control value of 1.18 +/- 0.13 X 10(-3) to 7.69 +/- 0.75 X 10(-3) cm3 X min-1 X g wet lung wt-1 and a decrease in the sigma from 0.96 +/- 0.01 to 0.74 +/- 0.02. The decrease in sigma suggests an increase in the calculated equivalent pore radius from 44 to 63 A. The results indicate that Ca2+ and Mg2+ play a role in the maintenance of normal pulmonary vascular permeability to proteins.
Insights
Calcium and magnesium are crucial for maintaining normal pulmonary vascular permeability. Lowering these cation concentrations significantly increases lung vascular permeability to proteins.
Area of Science:
- Pulmonary Physiology
- Cardiovascular Research
- Renal Physiology
Background:
- Pulmonary vascular permeability is a critical factor in maintaining lung fluid balance.
- The role of specific cations like calcium (Ca2+) and magnesium (Mg2+) in regulating this permeability is not fully understood.
Purpose of the Study:
- To investigate the impact of reduced perfusate calcium and magnesium concentrations on pulmonary vascular permeability.
- To quantify changes in albumin permeability-surface area product (PS) and albumin reflection coefficient (sigma) under these conditions.
Main Methods:
- Utilized an isolated perfused rabbit lung model.
- Administered ethylenediaminetetraacetic acid (EDTA) to decrease vascular Ca2+ and Mg2+ concentrations.
- Employed dual-tracer techniques with 125I- and 131I-labeled albumin to determine PS and sigma.
Main Results:
- A significant increase in the albumin permeability-surface area product (PS) was observed, rising from 1.18 x 10(-3) to 7.69 x 10(-3) cm3 min-1 g-1.
- The albumin reflection coefficient (sigma) decreased from 0.96 to 0.74, indicating increased protein passage.
- The calculated equivalent pore radius increased from 44 to 63 Angstroms.
Conclusions:
- Decreased perfusate concentrations of calcium and magnesium lead to a marked increase in pulmonary vascular permeability.
- These cations play a vital role in preserving the normal integrity and low protein permeability of the pulmonary vasculature.
- The findings suggest potential therapeutic targets for conditions involving altered lung vascular permeability.