DIFFERENTIAL REGULATION OF PHOSPHOLIPASE-D AND PHOSPHOLIPASE-C BY PROTEIN-KINASE-C-BETA AND PROTEIN-KINASE-C-DELTA IN LIVER MACROPHAGES

We have studied activation of phospholipase (PL) C and PLD in liver macrophages labelled with [H-3]arachidonic acid. Zymosan, phorbol 12-myristate 13-acetate (PMA), A23187 and fluoride but not arachidonic acid or lipopolysaccharide (LPS) induce an activation of PLD ([H-3]phosphatidylethanol (PEt) accumulation). An activation of PLC ([3H]diacylglycerol (DAG) accumulation) is measured with zymosan, PMA and fluoride but not with A23187, LPS or arachidonic acid whereas inositol phosphates are formed with zymosan, only. Removal of extracellular calcium reduces the formation of [H-3]PEt and [H-3]DAG while pretreatment of the cells with dexamethasone reduces [H-3]PEt formation, only. PMA- and zymosan-induced activation of PLD and PMA-induced activation of PLC both seem to be mediated by protein kinase (PK) C-beta whereas zymosan-induced activation of PLC is negatively controlled by PKC-delta. We could furthermore present evidence that the release of [H-3]arachidonic acid in these cells occurs independent of an activation of PLD.