Signal response transduction in rabbit neutrophil leucocytes. The effects of exogenous phospholipase A2 suggest two pathways exist.

Rabbit neutrophils stimulated by chemotactic peptide (fMLP) or phorbol ester (PMA) respond with a metabolic burst which can be assayed by following luminol-enhanced chemiluminescence. Depending upon the agonist used, exogenous bee-venom phospholipase A2 (PLA2) will enhance or inhibit the response. Neutrophil activation by fMLP is enhanced by PLA2 or by the addition of arachidonic acid, but unaffected by lysophosphatide. The cellular response to PMA is markedly inhibited by PLA2 or by lysophosphatide, though not completely abrogated, but is enhanced by arachidonic acid. The lysophosphatide inhibition overrides the arachidonic acid potentiation of the PMA-induced response. Neither PLA2 nor arachidonic acid alone will activate the cells; it seems that agonist is essential. We interpret these results to mean that at least two signal-response transduction systems are involved in agonist-induced metabolic activation of rabbit neutrophil leucocytes.