Liggins G C
Postgraduate School of Obstetrics and Gynaecology, University of Auckland, New Zealand.
Biol Neonate. 1989;55(6):366-75. doi: 10.1159/000242940.
Since arachidonic acid is the obligatory substrate for the synthesis of prostaglandins, the regulation of arachidonic acid from phospholipid stores is likely to be pivotal in the release of prostaglandins and the initiation of labour. The hydrolysis of phospholipids to yield arachidonic acid is catalysed by phospholipases of which there are two of particular importance. Phospholipase C mediates the action of certain agonists including oxytocin and acts specifically on phosphatidyl-inositol resulting in the release of inositol phosphates. Phospholipase A2 is activated by a variety of physical and chemical agents (e.g. infection, trauma) that increase calcium concentrations in the cell; it releases arachidonic acid from phosphatidyl-choline and phosphatidyl-ethanolamine in particular. Factors influencing phospholipase activity are important in the mechanism initiating labour whether preterm or term. A specific chorionic protein (gravidin) that inhibits activity of phospholipase A2 during pregnancy but loses its activity at the onset of labour has been identified and characterised.
由于花生四烯酸是合成前列腺素的必需底物，因此从磷脂储存中调节花生四烯酸可能在前列腺素的释放和分娩发动中起关键作用。磷脂水解产生花生四烯酸是由磷脂酶催化的，其中有两种磷脂酶特别重要。磷脂酶C介导某些激动剂（包括催产素）的作用，并特异性作用于磷脂酰肌醇，导致肌醇磷酸的释放。磷脂酶A2被多种物理和化学因子（如感染、创伤）激活，这些因子会增加细胞内的钙浓度；它尤其从磷脂酰胆碱和磷脂酰乙醇胺中释放花生四烯酸。影响磷脂酶活性的因素在早产或足月分娩发动机制中很重要。已鉴定并表征了一种特定的绒毛膜蛋白（妊娠素），它在怀孕期间抑制磷脂酶A2的活性，但在分娩开始时失去其活性。
