Clearance of instilled surfactant lipid from the lungs of unanesthetized sheep: lipids are differentially transported by nonlymphatic pathways.
The routes used by the lung to dispose of instilled exogenous surfactant lipid components were examined with the sheep chronic lung lymph fistula preparation. Small vesicles of radiolabeled dipalmitoyl phosphatidylcholine (DPPC) either alone or with radiolabeled cholesterol (CHOL) were instilled intratracheally, and samples of lung lymph and plasma were collected at 60-minute intervals for 12 hours. At any time point, the total amounts of either labeled DPPC or CHOL that appeared in lung lymph were small fractions (less than 0.5%) of their respective amounts in plasma. Labeled DPPC, as DPPC alone or as DPPC/CHOL (2:1 molar ratio), appeared simultaneously in plasma and lymph and displayed the same time course of appearance regardless of vesicle composition. CHOL appearance was also simultaneous in both plasma and lymph, but was distinctly slower than that of DPPC. The time differences noted between the appearance of labeled DPPC and CHOL in lymph and plasma indicate that these two lipid components of the instilled surfactant lipid component vesicles appear to be handled in different fashions during their transport from the lung. Further, the data obtained by sampling lung lymph suggest that the lung interstitial space may not play an active role in the transport of exogenously administered lipid from the lung.
D015060:1,2-Dipalmitoylphosphatidylcholine / Q000378:metabolism; D000818:Animals; D002784:Cholesterol / Q000378:metabolism; D008168:Lung / Q000098:blood supply / Q000378:metabolism*; D008208:Lymphatic System / Q000502:physiology; D008657:Metabolic Clearance Rate; D008833:Microcirculation; D011663:Pulmonary Surfactants / Q000378:metabolism*; D012756:Sheep
D011663:Pulmonary Surfactants; D015060:1,2-Dipalmitoylphosphatidylcholine; D002784:Cholesterol