Abstract
Extract: Using the radio-iodinated human serum albumin ([131I]-RISA) dilution method to measure lamb fetal pulmonary fluid (FPF) volume, we followed the disappearance of protein complexed, 14C-labeled phosphatidylcholine ([14C]PC) during the first 90 min after its injection into FPF. The FPF samples were analyzed for total lipid 14C activity and for distribution of 14C in PC, other phospholipids (PL), fatty acids (FA), and neutral lipids (NL). For most sampling periods ascending aortic (AAo) and right atrial (RA) blood samples were obtained simultaneously with FPF and serum was analyzed for total lipid 14C activity and for distribution of 14C in total PL, FA, and NL. These studies indicate that (1) PC is cleared rapidly from FPF with an estimated half-time of 15–57 min; (2) FPF-PC may be metabolized to lyso-PC and FA within the fluid itself; and (3) FA derived from FPF-PC enter the pulmonary circulation, thus establishing a pulmonary arteriovenous FA gradient. The possible sites at which PC may be cleared from FPF are considered.
Speculation: The novel possibility is suggested that FPF contains appropriate enzymes (phospholinase(s) for deacvlation of and also that PC-degradative enzymes are active at the surface of the alveolar epithelial cells. By comparison with results of others regarding the half-life of PC in the air-lung, it appears that PC clearance outside the cell (i.e., after secretion) occupies a relatively short period in the turnover of the molecule. Since the products of PC degradation appear in arterial blood as FA primarily, we may consider FPF as a possible source of serum FA.
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Scarpelli, E., Condorelli, S., Colacicco, G. et al. Lamb Fetal Pulmonary Fluid. II. Fate of Phosphatidylcholine. Pediatr Res 9, 195–201 (1975). https://doi.org/10.1203/00006450-197504000-00011
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DOI: https://doi.org/10.1203/00006450-197504000-00011