Original Article

Metabolic fate of platelet-activating factor (PAF, 1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine) and lyso-PAF (1-O-alkyl-2-lyso-sn-glycero-3-phosphocholine) in FRTL5 cells

Correspondence to: Athanassia Siafaka-Kapadai.

The metabolism of platelet-activating factor (PAF, 1-O-alkyl-2-acetyl-sn -glycero-3-phosphocholine) and lyso-PAF (1-O-alkyl-2-lyso-sn -glycero-3-phosphocholine) was investigated in FRTL5 cells, a normal rat thyroid cell line. FRTL5 cells incorporated [³H]PAF and deacetylated this compound to the corresponding [³H]lyso-PAF which was not accumulated or secreted but converted mainly to alkyl-acyl-phosphocholine indicating that this acylation process was particularly active in these cells. Among metabolic products of both [³H]PAF and [³H]lyso-PAF were alkylglycerol as well as its mono- and diacyl derivatives. [³H]alkylglycerol could be the intermediate compound for the production of [³H]alkyl- and [³H]alkenyl-phosphoethanolamine (plasmalogen) which were also metabolic products. FRTL5 cells were able to convert lyso-PAF to PAF especially when they were stimulated by ionophore A23187 in the presence of [³H]lyso-PAF and phenylmethylsulfonyl fluoride. The amount of PAF increased for the first 30 min and declined thereafter. PAF resting levels were found low in the same cells. Furthermore, PAF-acetylhydrolase activity was determined in cell homogenates.

The presence of metabolic products such as alkyl-phosphatidylcholine, alkyl- and alkenyl-phosphatidylethanolamine and alkyl-glycerol, as well as, its mono- and diacyl derivatives, indicates that FRTL5 cells and probably other thyroid cells, are very active in metabolizing PAF and lyso-PAF and suggests the co-operation of the corresponding metabolic pathways in these cells.—Botitsi, E., M. Mavri-Vavayanni, and A. Siafaka-Kapadai. Metabolic fate of platelet activating factor (PAF, 1-O-aklyl-2-acetyl-sn-glycero-3-phosphocholine) and lyso-PAF (1-O-alkyl-2-lyso-sn-glycero-3-phosphocholine) in FRTL5 cells. J. Lipid Res. 1998. 39: 1295–1304.

Supplementary key words: PAF metabolism, PAF biosynthesis, PAF-acetylhydrolase, plasmalogens, alkylglycerol, FRTL5 cells, thyroid

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