The effect of platelet-activating factor on histamine release from rat peritoneal mast cells

The effect of platelet-activating factor (PAF) on histamine release from peritoneal mast cells of adult and young male rats was investigated. PAF alone tended to release histamine from the mast cells of adult and young rats, although very slightly. On the other hand, PAF significantly inhibited the histamine release induced by the Ca2+ ionophore A23187 in mast cells obtained from rats of either age group, but not that by compound 48/80. Such inhibition was not seen with lyso-PAF. CV-3988, a PAF antagonist, antagonized the inhibitory effect of PAF on the A23187-induced histamine release in mast cells from adult and young rats. These results suggest that PAF does not have a strong histamine-liberating action on mast cells, and that PAF inhibits the calcium influx into mast cells through the activation of PAF receptors.