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Lung surfactant kinetics in conscious pigs
W Z Martini1, D L Chinkes, R E Barrow
1Shriners Burns Hospital, and Departments of Surgery and Anesthesiology, The University of Texas Medical Branch, Galveston, Texas 77555, USA.
The American Journal of Physiology
|July 17, 1999
Summary
Plasma free fatty acids (FFA) are the main source for synthesizing lung surfactant phosphatidylcholine (PC). De novo synthesized fatty acids contribute minimally to this essential pulmonary lipid production.
Area of Science:
- Pulmonary Physiology
- Lipid Metabolism
- Biochemistry
Background:
- Lung surfactant phosphatidylcholine (PC) is crucial for maintaining alveolar stability.
- Understanding the origins of fatty acids (FA) for PC synthesis is vital for respiratory health.
Purpose of the Study:
- To quantify the relative contributions of plasma free fatty acids (FFA) and de novo synthesized FA to lung surfactant PC synthesis.
- To investigate surfactant kinetics in pigs using a novel stable isotope tracer model.
Main Methods:
- Development of a stable isotope tracer model using [1, 2-(13)C(2)]acetate and [U-(13)C(16)]palmitate.
- Infusion of tracers in overnight fasted pigs under basal and low-dose glucose conditions.
- Quantification of surfactant PC-bound palmitate incorporation and secretion rates.
Main Results:
- Plasma palmitate incorporation into surfactant PC was significantly higher (20.9 nmol/h/g) than de novo synthesized palmitate (2.1 nmol/h/g).
- The secretion rate of PC-bound palmitate from lamellar bodies was 239 nmol/h/g.
- Approximately 90% of secreted PC was recycled for reutilization in lamellar bodies.
Conclusions:
- Plasma free fatty acids are the predominant source for lung surfactant PC synthesis.
- De novo fatty acid synthesis plays a minor role in surfactant PC production under the studied conditions.
- The lung efficiently recycles phosphatidylcholine for surfactant homeostasis.