Activation of Phospholipid Metabolism During Mediator Release from Stimulated Rat Mast Cells

Abstract

Abstract Phospholipid metabolism was studied during mediator release from highly purified rat mast cells. The incorporation of 32PO4 into individual phospholipids was determined after isolation of phospholipid classes by two-dimensional thin layer chromatography. Various stimulators of histamine release (anti-IgE antibody, concanavalin A [Con A], compound 48/80, or the ionophore A23187) increased 32PO4 incorporation into phosphatidic acid (PA), phosphatidylinositol (PI), and phosphatidylcholine (PC) 4- to 10-fold within 15 min. No change in 32PO4 incorporation into phosphatidylserine (PS), phosphatidylethanolamine, or sphingomyelin was detected. Anti-IgE antibody caused significantly increased labeling of PA within 8 sec and of PI and PC within 30 sec. The concentrations of anti-IgE and Con A causing threshold, half maximal, and maximal phospholipid labeling were slightly less than those required for comparable changes in histamine release. Both phospholipid labeling and mediator release in response to anti-IgE or Con A were enhanced 3- to 4-fold by PS. The addition of 50 mM α-methylmannoside to mast cells 10 min after challenge with Con A rapidly halted both ongoing mediator release and PA labeling. The results of these studies indicate that marked and selective changes in phospholipid metabolism occur before as well as during mediator release from mast cells and that these reactions may be an intrinsic part of the biochemical mechanisms that control mediator release.