Anti-inflammatory activity of bee venom peptide 401 (mast cell degranulating peptide) and compound 48/80 results from mast cell degranulation in vivo.

1. The relationship between the anti-inflammatory activity of the bee venom peptide 401 in the carrageenin-induced oedema of the rat hind paw and its mast cell degranulating activity has been reinvestigated. 2. Mast cell degranulation caused by compound 48/80 (10 mg kg-1) or by allergen challenge in rats sensitized to Nippostrongylus brasiliensis also suppressed rat hind paw oedema in the same test. 3. The anti-inflammatory activities of peptide 401 and compound 48/80 were partially suppressed by pretreatment of rats with mepyramine and methysergide, at doses (2.5 mg kg-1) that completely suppressed skin reactions to these mast cell-derived amines. Pretreatment of rats with compound 48/80 also suppressed the apparent anti-inflammatory actions of peptide 401 and of compound 48/80. 4. Injection of peptide 401 together with carrageenin increased the inflammatory response in the rat hind paw. 5. The anti-inflammatory activity of peptide 401 and of compound 48/80 in the carrageenin-induced swelling of the rat hind paw arises from mast cell degranulation in vivo.