PHOSPHOLIPASE-D IS ACTIVATED BY PHORBOL ESTER BUT NOT CSF-1 IN MURINE BONE-MARROW-DERIVED MACROPHAGES

Phospholipase D activity was measured in murine bone marrow-derived macrophages (BMM) treated with either colony stimulating factor-1 (CSF-1) or phorbol myristyl actetate (PMA) by measuring formation of phosphatidylbutanol (PtBut) in cells preloaded with n-butanol. Addition of 10(-7)M PMA for 15min stimulated the amount of PtBut formed in growth arrested cells by 3-4 fold whereas no stimulation was observed with 5000 units mL(-1) CSF-1 for 0.5, 2 or 15 min. Protein kinase C activity was determined in growth-arrested BMM by phosphorylation of Myristoylated Alanine-Rich C Kinase Substrate (MARCKS). PMA stimulation for 5min increased protein kinase C activity 5-6 fold whereas CSF-1 treatment for 5 min or 15 min did not. Contrary to earlier reports, CSF-1 did not stimulate diradyl glycerol formation in BMM. These results show that stimulation of protein kinase C and the activation of phospholipase D are not involved in the early events of CSF-1-stimulaled signal transduction pathways in BMM. B 1994 Academic Press, Inc.