Differences in polymorphonuclear leukocyte aggregating responses among several species in response to chemotactic stimulation.

We investigated some of the metabolic requirements for FMLP-induced aggregation, monitored spectrophotometrically at 37 degrees C in human, rabbit, and guinea pig p]olymorphonuclear leukocytes. Exposure of guinea pig polymorphonuclear leukocytes to the anaerobic glycolytic inhibitors 5 mM 2-deosy-glucose and 5 mM iodoacetamide inhibited aggregation, whereas 1 mM KCN was without effect. Ca++ and Mg++ were required for optimal aggregation; Mg++ alone partially supported aggregation, whereas Ca++ alone failed to do so. Verapamil, a divalent cationic blocker, inhibited polymorphonuclear leukocyte aggregation of all species in a dose-dependent fashion in the presence of Ca++ and Mg++ and blocked pseudopodia formation as monitored by transmission electron microscopy. Rabbit polymorphonuclear leukocytes were most response to FMLP and aggregated at concentrations as low as 2 x 10(-13)M in the presence of cytochalasin B. Cytochalasin B enhanced aggregation of both human and rabbit polymorphonuclear leukocytes but not guinea pig polymorphonuclear leukocytes in the presence of divalent cations. Unlike polymorphonuclear leukocytes from other species, cytochalasin B rabbit pretreated polymorphonuclear leukocytes aggregated even in the absence of divalent cations, and this response was completely blocked by verapamil. Human and guinea pig polymorphonuclear leukocytes demonstrated aggregatiopn responses only to concentrations as low as 2 x 10(-10)M FMLP. These studies show the unique aggregating responses of rabbit, human, and guinea pig polymorphonuclear leukocytes to FMLP and indicate the requirement for divalent cation transport and formation of pseudopia in this response for all species.