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Stop-flow studies of solute uptake in rat lungs
R M Effros1, R Schapira, K Presberg
1Division of Pulmonary and Critical Care Medicine, Department of Medicine, Medical College of Wisconsin, Milwaukee 53226; and Zablocki Veterans Affairs Medical Center, Milwaukee, Wisconsin 53295-1000, USA.
Journal of Applied Physiology (Bethesda, Md. : 1985)
|September 8, 1998
Summary
Stop-flow studies in isolated rat lungs reveal that potassium analogs like thallium-201 (201Tl+) and rubidium-86 (86Rb+) are taken up by lung exchange vessels. This uptake increases with longer stop intervals, indicating solute and water exchange.
Area of Science:
- Pulmonary Physiology
- Vascular Biology
- Solute Transport
Background:
- Understanding solute and water exchange in the pulmonary vasculature is crucial for respiratory health.
- Isolated rat lungs provide a model to study microvascular function and permeability.
- Previous methods lacked precision in quantifying exchange vessel dynamics.
Purpose of the Study:
- To characterize solute uptake in isolated rat lungs using stop-flow techniques.
- To investigate the influence of perfusion rate and stop interval duration on solute exchange.
- To determine the role of potassium analogs in assessing pulmonary vascular volume and exchange.
Main Methods:
- Isolated rat lungs were perfused with solutions containing albumin and various diffusible indicators (e.g., 201Tl+, 86Rb+, [3H]mannitol).
- Stop-flow periods (10-300 s) were implemented, followed by flushing to assess perfusate washout.
- Concentrations of indicators in venous outflow were measured to quantify uptake and vascular clearance.
Main Results:
- Potassium analogs (201Tl+, 86Rb+) showed decreased venous outflow concentrations post-stop-flow, indicating uptake into exchange vessels.
- Uptake of 201Tl+ and 86Rb+ increased with longer stop intervals, with near-maximal uptake by 90 seconds.
- Increased perfusate potassium reduced the cleared vascular volume for 201Tl+ and 86Rb+.
- Uptake of [3H]mannitol, [14C]urea, and 3HOH was limited to high-flow, short-duration loading.
Conclusions:
- Stop-flow technique effectively quantifies solute uptake in pulmonary exchange vessels.
- Potassium analogs are valuable for determining the volume of pulmonary vasculature involved in exchange.
- The findings provide insights into the distribution of solute and water exchange along the pulmonary vasculature.