Reutilization of phosphatidylcholine analogues by the pulmonary surfactant system. The lack of specificity.
Five specific 14C-labelled analogues of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine, (L-alpha-DPPC) including 1-palmitoyl-sn-glycero-3-phosphocholine, (L-alpha-lysoPC) and 2,3-dipalmitoyl-sn-glycero-1-phosphocholine (the D isomer of DPPC) were individually mixed with L-alpha-[3H]DPPC and unlabelled natural surfactant isolated from 3-day-old rabbits. The mixtures were injected intratracheally into 3-day-old rabbits which were then killed at preset times up to 72 h after injection. Phosphatidylcholine was isolated from the alveolar wash and from lamellar body fraction from each rabbit and was analyzed for the ratio of 3H-to-14C counts/min. These ratios were plotted against the time the rabbits were killed to determine whether a difference existed in the rates of reutilization of the analogues relative to L-alpha-DPPC. By 60 h L-alpha-lysoPC was reutilized at 42% of the efficiency of the L-alpha-[3H]DPPC with which it was injected. That part of the L-alpha-lyso which was reutilized had been converted to [14C]phosphatidylcholine. Each of the other four analogues was reutilized by the surfactant system as efficiently as L-alpha-DPPC. These results are most consistent with a process of bulk uptake of surfactant from the alveolar space by the Type II cell with subsequent processing for resecretion which involves minimal specificity for molecular structure.
D000818:Animals; D007536:Isomerism; D008168:Lung / Q000378:metabolism; D008244:Lysophosphatidylcholines / Q000378:metabolism; D010713:Phosphatidylcholines / Q000378:metabolism*; D010741:Phospholipases A / Q000378:metabolism; D011663:Pulmonary Surfactants / Q000378:metabolism*; D011817:Rabbits; D013379:Substrate Specificity
D008244:Lysophosphatidylcholines; D010713:Phosphatidylcholines; D011663:Pulmonary Surfactants; D010741:Phospholipases A