PHAGOCYTOSIS STIMULATES THE RELEASE OF A SLOW REACTING SUBSTANCE IN CULTURED MACROPHAGES

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Abstract
A slow‐reacting substance (SRS) was released from non‐elicited mouse peritoneal macrophages during phagocytosis of zymosan particles, whereas no detectable SRS was produced by resting cells. The macrophage SRS induced a delayed and slow contraction of the guinea‐pig ileum but not of the chick rectum. The myotonic activity was antagonized by low concentrations of FPL 55712 (sodium 7‐[3‐(4‐acetyl‐3‐hydroxy‐2‐propylphenoxy)‐2‐hydroxypropoxy]‐4‐oxo‐8‐propyl‐4H‐1‐benzopyran‐2 carboxylate) but was not affected by mepyramine or hyoscine, and was not associated with tachyphylaxis. SRS release was increased by indomethacin and was abolished by the lipoxygenase and cyclo‐oxygenase inhibitor, BW755C (3‐amino‐1‐[m‐(trifluoromethyl)‐phenyl]‐2‐pyrazoline). Addition of exogenous arachidonic acid or cysteine enhanced SRS production.