Effect of calcium, magnesium, and cytochalasin B on arachidonic acid-induced neutrophil aggregation

Abstract

Suspended in media containing calcium and magnesium, human neutrophils aggregate briefly when exposed to arachidonic acid. The magnitude and duration of this response was enhanced by the presence of increased magnesium concentration, increased magnesium plus calcium concentrations, and cytochalasin B. The response was inhibited by increased calcium concentrations. When calcium, magnesium, or both bivalent cations were omitted from the cell suspension, the response did not occur. Since various chemotatic factors also briefly aggregate neutrophils and since these chemotatic factor-induced responses are similarly influenced by the bivalent cations and cytochalasin B, a close association between the bioactivities of arachidonic acid and chemotactic factors is evident. The aggregation response to both types of stimuli may share common intracellular mechanisms.

Neutrophil Aggregation: Evidence for a Different Mechanism of Action by Phorbol Myristate Acetate

“…Chemotactic factors, A23 187, and arachidonic acid aggregate PMNs but their potency is comparatively modest. None of these agents aggregate PMNs suspended in calcium-free medium; indeed, their action requires comparatively high concentrations of both calcium and magnesium in order to induce detectable effects (17,18). Only A23 187 irreversibly aggregates the cells (18); chemotactic factors and arachidonic acid induce responses which reverse within minutes ( 5 , 18).…”

“…On a molar basis, they are active only at one to three orders of magnitude greater concentrations than PMA and, in general, their effects are much less prominent at all concentrations (1,5,18,25,44,45). Cytochalasin B dramatically enhances [ 1,[17][18][19]23, 251 whereas 100 p M indomethacin (6, 25), 10 p M ETYA (6,25), and 10 p M NDGA (personal observation) totally abrogate the response to these agents. None of these agents aggregate PMNs suspended in calcium-free medium; indeed, their action requires comparatively high concentrations of both calcium and magnesium in order to induce detectable effects (17,18).…”

“…For instance, blockers of arachidonic acid metabolism inhibit not only the arachidonate-induced responses (1, 2) but also the responses of aggregation, degranulation, and generation of reactive oxygen-containing species evoked by chemotactic factors (2-5) and A23187 (2,6). It is also implicated in PMN responses to other stimuli.…”