HISTAMINE-SECRETION FROM MAST-CELLS STIMULATED WITH PLATELET-ACTIVATING-FACTOR (PAF)

Platelet activating factor (PAF) produced a dose-dependent release of histamine from rat peritoneal mast cells. The release was non-cytotoxic at 5-mu-M but cytotoxic at a concentration of 10-mu-M and above. Isolated tissue mast cells of the rat, guinea-pig and man showed varying responses to PAF but the release was again generally cytotoxic. The non-cytotoxic release from rat serosal mast cells stimulated with low concentrations of PAF was potently inhibited by phosphodiesterase inhibitors, cAMP-active drugs and the naturally occurring flavonoid quercetin. The release was also selectively inhibited by the specific PAF antagonist BN 50730 but not by BN 52021 or WEB 2086. These findings suggest that PAF may interact with the mast cell membrane to produce mediator release, rather than acting via a specific receptor.