Histamine release induced from mast cells by active components of compound [formula omitted

Abstract

Compound 48 80 and 14C-labeled compound 48 80 were synthesized, and fractionatd by thin-layer chromatography into 14 components (AN) with various histamine releasing activities and different Ca 2+ requirements for their actions. The histamine release induced from rat mast cells in vitro by the most active component, fraction D (molecular weight = 2280, a tridecamer composed of 13 monomer units), was greatly enhaced by extracellular Ca 2+ and was partially reduced by pretreatment of the cells with dinitrophenylated ascaris antiserum, an IgE. In contrast, the histamine release induced by fraction H (molecular weight = 1580, a nonamer composed of 9 monomer units), was higher in Ca 2+-free medium than in Ca 2+-containing medium, and was partially reduced by pretreatment of mast cells with neurotensin or substance P, Ca 2+-independent releasers. Apperently both fractions D and H are useful reagents for investigating the role of Ca 2+ in histamine release and releaser binding in mast cells.