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Tsutsumi T, Tokumura A, Yamaguchi M, Kitazawa S, Tanigawara Y: Phorbol myristate acetate stimulates degradation of a structural analogue of platelet-activating factor to a neutral lipid in human leukemic K562 cells: relevance to the release of lipids. Biol Pharm Bull. 2004 Jan;27(1):24-8.
In our attempt to investigate the mechanism of the release of platelet-activating factor (PAF) from cells, the erythroleukemic cell line K562 was preloaded with a radiolabeled PAF analogue having an ethylcarbamyl residue, 1-O-octadecyl-2-O-ethylcarbamyl-sn-glycero-3-phosphocholine (ethylcarbamyl-PAF), that is resistant to the hydrolytic action of PAF acetylhydrolase. Its extracellular release was monitored using an albumin back-extraction method, and its metabolic degradation was analyzed by TLC. Phorbol myristate acetate (PMA) was found to stimulate the release of two radioactive lipids, ethylcarbamyl-PAF itself and its metabolite, 1-O-octadecyl-2-ethylcarbamyl-sn-glycerol, whereas only ethylcarbamyl-PAF was released from the resting cells. The increased release of radioactive lipids in PMA-stimulated cells was suggested to be due to stimulated degradation of intracellular ethylcarbamyl-PAF into the cell-permeable metabolite. Thus K562 cells have much less capacity to release intact PAF-like lipid in comparison with its high ability to uptake exogenously added PAF analogues previously described by us and others. |
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