Platelet-activating factor mediates phosphatidylcholine hydrolysis by phospholipase D in human endometrium.
Human preimplantation embryos and endometrium secrete platelet-activating factor (PAF). The mechanism of phosphatidylcholine (PC) degradation stimulated by PAF was investigated in endometrial explants prelabeled with [methyl-3H]choline or preincubated with [3H]butan-1-ol. Analysis of the water-soluble metabolites of PAF-induced PC hydrolysis in secretory endometrium demonstrated that the stimulated generation of [3H]choline ([3H]Cho) precedes that of [3H]choline phosphate ([3H]ChoP) and [3H]glycerophosphocholine ([3H]GPC). Within 30 sec there was a rapid rise in PAF-induced [3H]Cho generation and by 2 min this had increased to 59.9% +/- 10.6% (p less than 0.02), with no effect upon [3H]ChoP and [3H]GPC during this period. Both [3H]GPC and [3H]ChoP, however, were increased at a later time point. The slower [3H]ChoP generation may suggest that PC-specific phospholipase C activation as well as delayed [3H]GPC rise may be due to PC-specific phospholipase A2 and lysophospholipase activation. Phospholipase D activity was confirmed by the incorporation of high-specific-activity [3H]butan-1-ol into [3H]phosphatidylbutanol ([3H]PBut). The rapid generation of [3H]PBut, which paralleled the rise in intracellular [3H]Cho, strongly suggests that PC breakdown is catalyzed by the phospholipase D pathway. It is proposed that PAF induces PC hydrolysis as a consequence of an early phospholipase D-catalyzed breakdown of PC in human secretory endometrium. This may be an alternative source for prostaglandin synthesis and an important pathway essential for long-term activation of local cellular events at the time of implantation.
Ahmed
A
A
Department of Obstetrics and Gynaecology, University of Cambridge, Rosie Maternity Hospital, United Kingdom.
Ferriani
R A
RA
Plevin
R
R
Smith
S K
SK
D002794:Choline / Q000378:metabolism; D002852:Chromatography, Ion Exchange; D004305:Dose-Response Relationship, Drug; D004717:Endometrium / Q000187:drug effects / Q000378:metabolism*; D005260:Female; D006801:Humans; D006868:Hydrolysis / Q000187:drug effects; D010713:Phosphatidylcholines / Q000378:metabolism*; D010739:Phospholipase D / Q000494:pharmacology*; D010972:Platelet Activating Factor / Q000502:physiology*; D014316:Tritium
D010713:Phosphatidylcholines; D010972:Platelet Activating Factor; D014316:Tritium; D010739:Phospholipase D; D002794:Choline