Suppression of ConA-induced inflammatory ascites by lipopolysaccharide (LPS) in mice

The effect of pre-treatment with Escherichia coli O83 lipopolysaccharide (LPS) on concanavalin A-induced ascites was examined. The LPS was injected intraperitoneally (i.p.) in different doses to mice, and then ascites was induced by i.p. administration of concanavalin A (ConA) (25 mg/kg b.w.). After 2.5 h the mice were killed and the ascitic fluid was collected and measured. The LPS produced a marked and dose-dependent inhibition of ConA-induced ascites and the effect of pre-treatment lasted up to almost a week. Complete inhibition could not be achieved. If administered alone, LPS did not produce ascites.It is well known that LPS enhances vascular permeability in several tissues, but the present work shows that peritoneal permeability is not enhanced by this agent. Suppression of ConA-induces ascites may be explained by the hypotonic effect of LPS.