Hoffman D R, Truong C T, Johnston J M
Am J Obstet Gynecol. 1986 Jul;155(1):70-5. doi: 10.1016/0002-9378(86)90081-5.
The presence of the potent bioactive glycerophospholipid 1-alkyl-2-acetyl-sn-glycero-3-phosphocholine (platelet-activating factor) in a lamellar body-enriched fraction of amniotic fluid from women in labor has prompted the present investigation to examine the fetal lung as the possible tissue source of this platelet-activating factor. The metabolism of platelet-activating factor was assessed in an organ culture system in which human fetal lung tissue (12 to 16 weeks) was incubated for 6 to 7 days. During this period, the type II pneumonocytes differentiate and surfactant glycerophospholipid biosynthesis is greatly enhanced. The initial specific activity of the platelet-activating factor biosynthetic enzyme lyso-platelet-activating factor:acetyl-coenzyme A acetyltransferase is two to three times greater in microsomes prepared from fetal lung than in those from the fetal liver or kidney. The specific activity of acetyltransferase in lung tissue increased twofold after 6 days in organ culture. A similar increase in acetyltransferase activity was found in the lamellar body-enriched (18,000 X g) subcellular fraction of fetal lung. The activity of the major platelet-activating factor-inactivating enzyme platelet-activating factor acetylhydrolase did not change significantly in the lung explants during the incubation period. Associated with the enhanced platelet-activating factor biosynthetic activity in the fetal lung was an increase in the platelet-activating factor concentration, from 17 to 37 fmol/mg of protein between days 0 and 6 of culture. Corresponding increases of 3.3- and 3.8-fold in the concentrations of the platelet-activating factor lipid precursors lyso-platelet-activating factor and the 2-acyl congener were found after 6 days in culture. A reciprocal relationship was found between platelet-activating factor and glycogen content as the lung tissue matured in vitro; specifically, as the platelet-activating factor level increased, glycogen decreased from 340 to 77 micrograms/mg of protein. We suggest that platelet-activating factor may mediate the onset of glycogenolysis in fetal lung tissue similar to that in the isolated, perfused rat liver (Shukla SD, Buxton DB, Olson MS, Hanahan DJ. Acetylglyceryl ether phosphorylcholine. A potent activator of hepatic phosphoinositide metabolism and glycogenolysis. J Biol Chem 1983; 258:10212-4). The increased rate of glycogen degradation may serve as the carbon and energy source for the increased synthesis of glycerophospholipids required for surfactant production.(ABSTRACT TRUNCATED AT 400 WORDS)
分娩期妇女羊水富含板层小体的部分中存在强效生物活性甘油磷脂1-烷基-2-乙酰基-sn-甘油-3-磷酸胆碱（血小板活化因子），这促使本研究检查胎儿肺脏作为该血小板活化因子可能的组织来源。在一个器官培养系统中评估血小板活化因子的代谢，其中将人胎儿肺组织（12至16周）孵育6至7天。在此期间，II型肺上皮细胞分化，表面活性物质甘油磷脂生物合成大大增强。从胎儿肺制备的微粒体中，血小板活化因子生物合成酶溶血血小板活化因子：乙酰辅酶A乙酰转移酶的初始比活性比从胎儿肝脏或肾脏制备的微粒体高两到三倍。在器官培养6天后，肺组织中乙酰转移酶的比活性增加了两倍。在富含板层小体（18,000×g）的胎儿肺亚细胞部分中也发现乙酰转移酶活性有类似增加。在孵育期间，主要的血小板活化因子失活酶血小板活化因子乙酰水解酶的活性在肺外植体中没有明显变化。与胎儿肺中血小板活化因子生物合成活性增强相关的是血小板活化因子浓度增加，从培养第0天到第6天，从17 fmol/mg蛋白质增加到37 fmol/mg蛋白质。培养6天后，发现血小板活化因子脂质前体溶血血小板活化因子和2-酰基同系物的浓度相应增加了3.3倍和3.8倍。在体外肺组织成熟过程中，发现血小板活化因子与糖原含量之间存在相互关系；具体而言，随着血小板活化因子水平升高，糖原从340微克/毫克蛋白质降至77微克/毫克蛋白质。我们认为血小板活化因子可能介导胎儿肺组织中糖原分解的开始，类似于在分离的灌注大鼠肝脏中（Shukla SD，Buxton DB，Olson MS，Hanahan DJ。乙酰甘油醚磷酸胆碱。一种强效的肝磷酸肌醇代谢和糖原分解激活剂。《生物化学杂志》1983年；258：10212 - 4）。糖原降解速率的增加可能作为表面活性物质产生所需甘油磷脂合成增加的碳和能量来源。（摘要截断于400字）
