Increased phospholipase a activity and formation of communicative contacts between Acanthamoeba castellanii cells: Effect of 3′,5′-Cyclic AMP

Abstract 1. 1. Exogenous 1-palmitoyl- sn -glycero-3-phosphorylcholine becomes incorporated into the membrane of A. castellanii within 2 min of incubation. 2. 2. Homogenates of A. castellanii are shown to contain phospholipase A activity. 3. 3. The phospholipase A activity is dependent on the population density of the culture. 4. 4. An increased phospholipase A activity in older cultures of A. castellanii , due to an increased population density, induces aggregation of these cells in a way that communicative contacts are formed. 5. 5. At pH 5.5, the pH value at which the cells were grown, the phospholipase A activity is stimulated by cAMP; at pH 8.0 no stimulation occurs.