Abstract
Ethanolamine plasmalogens (1-alk-1′-enyl-2-acyl- sn-glycero-3-phosphoethanolamines) of many tissues contain high levels of arachidonate at their 2-position, and in certain tissues have been implicated as possible donors of arachidonate required in the synthesis of prostaglandins and thromboxanes. In the present study, [ 3H]arachidonate-labeled phospholipids of HSDM 1C 1 cells, a cell line derived from a mouse fibrosarcoma, were examined to determine the donor of the arachidonic acid released upon bradykinin stimulation of the synthesis of PGE 2. HSDM 1C 1 cells labeled with [ 3H]arachidonic acid for 24 hr in serum-free medium were used in most of the experiments and had the following distribution of label among the cellular lipids; phosphatidylcholine (33%), phosphatidylinositol (20%), diacyl- sn-glycero-3-phosphoethanolamine (15%), ethanolamine plasmalogen (15%), and less polar lipids (16%). Bradykinin treatment stimulated a rapid hydrolysis of [ 3H]arachidonate from the cellular lipids and conversion of the released acid to PGE 2, which was secreted into the medium. The label was released predominantly from phosphatidylinositol and possibly from phosphatidylcholine with no detectable change in the labeling of diacyl- or 1-alk-1′-enyl-2-acyl- sn-glycero-3-phosphoethanolamine. The ethanolamine plasmalogens, therefore, do not appear to be involved in the stimulated release of arachidonate in the HSDM 1C 1 cells. Indomethacin blocked the bradykinin-stimulated synthesis of PGE 2 and to a lesser degree inhibited the release of [ 3H]-arachidonate from the cellular lipids into the medium.
Published Version
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