Reactive oxygen species generation and histamine release by activated mastcells: modulation by nitric oxide synthase inhibition

1 We have examined the generation of intracellular reactive oxygen species (ROS) and release of histamine by rat peritoneal mast cells (RPMC) in respo nse to stimulation with antigen (ovalbumin), compound 48/80, nerve growth f actor (NGF) and substance P (SP). 2 We have also examined the effects of the non-specific nitric oxide syntha se inhibitor, L-NAME (100 mu M) upon the release of histamine and generatio n of intracellular ROS in response to the named secretagogues. 3 Ovalbumin (100-1000 mu g ml(-1)), compound 48/80 (0.1-100 mu g ml(-1)), N GF (0.1-100 mu g ml(-1)), and SP (5-50 mu M), caused a concentration-depend ent release of histamine from RPMC. 4 Ovalbumin (1 ng ml(-1)-0.1 mu g ml(-1)), compound 48/80 (1-100 mu g ml(-1 )), NGF (1 pg ml(-1)-1 mu g ml(-1)), and SP (0.005-50 mu M) caused a concen tration-dependent generation of intracellular ROS by RPMC. 5 Pre-incubation of RPMC with L-NAME (100 mu M) caused a significant enhanc ement of both histamine release and intracellular ROS from RPMC in response to ovalbumin, compound 48/80, NGF and SP. 6 Our data demonstrate that NGF, SP and ovalbumin are capable of causing in tracellular ROS generation by RPMC at lower concentrations than those causi ng significant histamine release and we speculate that this may contribute to the activation of cytokine production. 7 The data also show that NO modulates histamine release, and ROS generatio n in response to the secretagogues used. This may have significance in path ologies where NO synthesis is decreased, leading to an increased activation of mast cells.