Synergism between platelet-activating factor and diacylglycerol in the induction of superoxide anion production in guinea pig polymorphonuclear leukocytes.

The superoxide anion (O2-) production of guinea pig polymorphonuclear leukocytes (PMNL) by platelet-activating factor (PAF) was greatly enhanced by the addition of 1-oleoyl-2-acetylglycerol (OAG), even at low concentrations of OAG at which O2- production was little induced. The enhanced production was biphasic, depending on concentrations of PAF. One was saturable at a lower concentration range of PAF and probably mediated through a putative PAF receptor-islet-activating protein-sensitive GTP-binding protein (G protein) pathway. Another was increased in a concentration-dependent manner at a higher concentration range of PAF and apparently mediated through both receptor-G protein-dependent and -independent pathways. These results suggest that at least two types of action of PAF are involved in the synergistic stimulation of O2- production by PAF and OAG in PMNL.