IDENTIFICATION OF PHOSPHOLIPASE-D (PLD) ACTIVITY IN MOUSE PERITONEAL-MACROPHAGES

It is now believed that PLD may contribute to the sustained generation of diacylglycerol (DAG) within activated cells. DAG can be formed from phosphatidylcholine by the sequential actions of PLD and phosphatidic acid phosphohydrolase. Phorbal myristate acetate (PMA, 1 muM), A23187 (10 muM) or platelet-activating factor (PAF, 100 nM) caused significant enhancement of intracellular C-14-phosphatidic acid levels 2-5 min after the addition of stimulus, in cultures of peritoneal macrophages pre-labelled with C-14-palmitate. Bacterial lipopolysaccharide (LPS) (5 mug/ml) or zymosan (375 mug/ml) also stimulated the production of C-14-phosphatidic acid, but over a longer time course (15-60 min). In the presence of 1 % ethanol each stimulus caused significant production of 4C-phosphatidylethanol at the expense of C-14-phosphatidic acid, thus confirming a contribution of PLD in these reactions. This is the first report of PLD activity in this cell type.