EFFECT OF OCTADECYLMETHYLGLYCEROPHOSPHOCHOLINE AND HEXADECYLMETHYLGLYCEROL ON ARACHIDONIC ACYLATION OR RELEASE IN MACROPHAGES

O-Octadecyl-2-O-methyl-sn-glycero-3-phosphocholine (ET-18-O-CH3) and 1 -O-hexadecyl-2-O-methyl-sn-glycerol (hexadecylmethylglycerol) are dial kylglycerolipids poorly split by the lipolytic enzymes which can activ ate macrophages in culture. This study concerned the incorporation of [H-3]arachidonate into glycerolipids of rat peritoneal macrophages and its subsequent release. Cells cultured with ET-18-O-CH3 or hexadecylm ethylglycerol were labelled according to two procedures: (1) Cells wer e incubated first with dialkylglycerolipid and then with the tritiated arachidonate: hexadecylmethylglycerol was practically inactive. ET-18 -O-CH3 inhibited acylation of arachidonate in cell glycerophospholipid s (50%) and triglycerides (60%) during de novo glycerolipid synthesis, resulting in increased fatty acid radioactivity in cells. Both dialky lglycerolipids induced the release of tritiated eicosanoids and fatty acids in the medium. (2) Cells previously labelled with [H-3]arachidon ate were incubated with dialkylglycerolipid. Prelabelled glycerophosph olipids and triglycerides were only slightly affected by ET-18-O-CH3 w hich was nonetheless more efficient than hexadecylmethylglycerol in de creasing cell triglyceride (50%) and glycerophospholipid (10%) synthes is. Both induced the release of eicosanoids and fatty acids into the m edium. It is concluded that these agents, particularly ET-18-O-CH3, al lowed moderate but significant amounts of eicosanoids and fatty acids to be maintained in the medium.