Role of resident peritoneal cells in eosinophil migration induced by saline

In the present study, we investigated the role of resident peritoneal cells as well as the mediators involved in the eosinophil migration induced by large volumes of physiological saline. Two consecutive intraperitoneal injections of saline given 48 h apart, induced a selective recruitment of eosinophils into the cavity. This response was not observed with phosphate-buffered saline (PBS). Saline-induced eosinophil migration may be mediated at least in part by LTB4, since the lipoxygenase inhibitors BW A4C and MK 886 prevented the response. In the presence of saline, but not of PBS, mast cells and macrophages incubated in vitro released a factor which induced eosinophil migration when injected into the peritoneal cavity of rats. This release was inhibited by BW A4C and MK 886. These results indicate the importance of mast cells and macrophages in the eosinophil migration induced by saline and suggest the participation of LTB4 in this phenomenon. An abrupt reduction in the extracellular potassium concentration at the membrane of resident cells may be responsible for the saline effects since addition of potassium ions to saline abolished the eosinophil chemotactic activity of the same as well as its ability to stimulate the release of eosinophil chemotactic factor in vitro. Dexamethasone blocked both the saline-induced eosinophil migration and the release of eosinophil chemotactic factor by mast cells and macrophages. Pretreatment of the animals with dexamethasone inhibited the eosinophil migration induced either by the supernatants of saline-stimulated mast cells and macrophages or by LTB4. These results indicate that the release of additional mediators is necessary in order to account for the final eosinophil migration.(ABSTRACT TRUNCATED AT 250 WORDS)