Molecular Pharmacology, Vol 19, 31-37, Copyright © 1981 by the American Society for Pharmacology and Experimental Therapeutics

On the Relationship between Formylmethionyl-Leucyl-Phenylalanine Stimulation of Arachidonyl Phosphatidylinositol Turnover and Lysosomal Enzyme Secretion by Rabbit Neutrophils

¹ Department of Pharmacology, Medical College of Virginia, Richmond, Virginia 23298

The addition of the synthetic chemotactic peptide formylmethionyl-leucyl-phenylalanine (fMet-Leu-Phe) to rabbit neutrophils promoted [¹⁴C]arachidonic acid incorporation into phosphatidylinositol and lysosomal enzyme release; these two processes increased in parallel with respect to time and peptide concentration and were dependent upon extracellular Ca²⁺. Cytochalasin B, which augments enzyme release, also enhanced fMet-Leu-Phe-evoked arachidonyl phosphatidylinositol turnover. The peptide did not alter the incorporation of labeled palmitic acid or glycerol into phosphatidylinositol, although ³²P turnover was increased within 2 min. Another synthetic peptide, methionyl-leucyl-phenylalanine, failed to enhance arachidonic acid incorporation into phosphatidylinositol and was unable to promote lysosomal enzyme secretion. These results support the hypothesis that fMet-Leu-Phe-induced stimulation of lysosomal enzyme release and Ca²⁺-dependent turnover of arachidonyl phosphatidylinositol are somehow related. These findings, taken together with our previous studies demonstrating similar changes in membrane phospholipids during ACTH action on adrenocortical cells, suggest that the turnover of arachidonic acid in phospholipids mediated by a Ca²⁺-dependent phospholipase A₂ may represent a general mechanism for producing rapid perturbations in the cell membrane during accelerated secretory activity.