To clarify the effect of Asp-hemolysin-related synthetic peptide (P-21) on lipopolysaccharide (LPS)-induced nitric oxide (NO) production in murine peritoneal macrophages (Mφ) was demonstrated this study. P-21 inhibited LPS (from Escherichia coli O111 : B4) -induced NO production of Mφ in a dose-dependent manner. P-21 slightly effected on NO production induced by LPS from Klebsiella pneumonias in Mφ. The inhibition ability of the P-21 was influenced by differences of LPS from various strains. These results suggest that P-21 has effects on the bioactivity of LPS, such as NO production in Mφ
