Characterization of antichemotactic factor extracted from the gastric mucosa of rats

The gastric mucosa of normal rats exhibits no detectable inflammation or visible damage. We examined the effect of the gastric mucosal extract of rats on neutrophil chemotaxis and tried to purify antichemotactic factor. The chemotaxis of neutrophils was examined by the modified Boyden's method. After mucosal layer was scraped and then homogenized and centrifuged at 20,000 x g for 30 min, the supernatant was used as rat gastric mucosal extract (RGME). Prior exposure of neutrophils to the gastric mucosal extract caused a dose-dependent reduction in the neutrophil migration induced by formyl-methionyl-leucyl-phenylalanine (FMLP), leukotriene B4 (LTB4) and interleukin 8 (IL-8) without affecting the cell viability. The antichemotactic factor was partially purified by lectin affinity chromatography on wheat germ lectin (WGL)-Sepharose, anion exchange chromatography on Mono-Q and gel filtration on Superose 12. The molecular weight of the antichemotactic factor was estimated to be around 60 k by gel filtration. The activity was markedly abolished by boiling for 5 min, heating at 60 degrees C for 30 min, and treatment with 1% acetic acid, 0.1 M Na2CO3 or trypsin. Furthermore, the FMLP-induced migration of neutrophils pretreated with the antichemotactic factor for 5 min followed by washing with fresh medium was inhibited, although the factor was not added to the chamber. These results suggest that the gastric mucosa of rats intrinsically generates an antichemotactic factor which might play a crucial role in maintenance of the integrity of the gastric mucosa.