INFLUENCE OF ALKYL CHAIN LENGTHS IN DIALKYLGLYCEROPHOSPHOCHOLINES TOWARDS PHOSPHOLIPASE A(2) INHIBITION IN MACROPHAGES

Rat peritoneal macrophages were cultured with a specific and potent ph ospholipase A(2) activator A 23187, with 1-stearoyl-2-[H-3]arachidonoy l-sn-GPC as source of [H-3] arachidonic acid, and with a dialkyl-GPC, at 2, 10 or 20 mu M. Four dialkyl-GPCs were prepared by chemical synth esis. Position 2 of rac-glycerol was alkylated with an alkane chain of 8 carbons and position 1 was alkylated with various alkane chains (8, 10, 12, or 16 carbons). [H-3] arachidonic acid was split, then recove red with cell nonesterified fatty acids and nonphosphorous glycerolipi ds after endocellular phospholipase A(2) activity. It was also recover ed with fatty acids and eicosanoids isolated from culture medium. Inhi bition of fatty acid release and eicosanoid synthesis depended on mixe d chain dialkyl-GPC structures. The highest inhibitory effect on arach idonic acid release was reached with 1-decyl-2octyl-GPC and was practi cally as high in culture medium (IC50 at 5 mu M) as in cells (IC50 at 4 mu M). 1,2-di-octyl-GPC and 1-dodecyl-2-octyl-GPC had weaker inhibit ory effects (but higher in culture medium than in cells). The asymmetr ical 1-hexadecyl-2-octyl-GPC poorly affected enzyme activity.