Polymorphonuclear leucocyte membrane-stimulated oxidative metabolic activity---the effect of divalent cations and...

The effect of divalent cations and cytochalasins on the oxidative metabolic response of polymorphonuclear leucocytes (PMNL) following membrane stimulation by opsonized zymosan, phorbol myristate acetate (PMA), digitonin and n-formyl-methionyl-leucyl-phenylalanine (FMLP) was investigated using several techniques. For optimal ferricytochrome C reduction, oxygen consumption, luminol- and lucigenin-dependent chemiluminescence by PMNL on exposure to opsonized zymosan, extracellular magnesium was necessary. In contrast FMLP- and digitonin-induced PMNL metabolic activities were less dependent on extracellular magnesium than on calcium. Phorbol myristate acetate-induced PMNL oxidative metabolic activity occurred independently of extracellular magnesium and calcium concentration. Incubation of PMNL with cytochalasins B and E had little effect on PMA-induced metabolic activity, enhanced FMLP-induced metabolic activity but inhibited digitonin-induced metabolic activity. Investigation of zymosan-induced PMNL metabolic activity after incubation with cytochalasins demonstrated a dissociation between the different parameters of metabolic activity measured. The results described in this study support the suggestion that PMNL oxidative metabolism can be activated by at least two different mechanisms depending on the stimulus used, and that these mechanisms can in part be differentiated by their dependence on extracellular divalent cations.