The effects of substance P on histamine and 5‐hydroxytryptamine release in the rat

Abstract

Substance P (SP) induces histamine release from isolated rat peritoneal mast cells at concentrations of 0.1-10 .mu.M. Inhibitors of glycolysis and oxidative phosphorylation prevent the release of histamine induced by SP. Cells heated to 47.degree. C for 20 min release histamine when treated with an agent causing cell lysis but fail to release histamine in response to SP. SP does not release histamine by interacting with cell-bound IgE. Histamine release by SP is rapid, with more than 90% of the response occurring within 1 min of the addition of the peptide to mast cells at 37.degree. C. Substance P, unlike antigen-antibody or compound 48/80, does not show enhanced release of histamine when Ca (0.1-1 mM) is present in the extracellular medium but Ca increases the response to SP when the ion is added after the peptide. Extracellular Ca (0.1-1 mM), Mg (1-10 mM) and cobalt (0.01-0.1 mM) all inhibit SP-induced histamine release when added before the peptide. Pre-treatment of the cells with EDTA (10 mM) and washing in Ca-free medium inhibits the histamine release induced by SP. Histamine release induced by SP was optimum at an extracellular pH of 7.2. A number of peptides structurally related to SP were examined for histamine-releasing activity. At the concentrations tested, the N-terminal dipeptides Lys-Pro and Arg-Pro, tuftsin, physalaemin, eledoisin, SP3-11, SP4-11 and [p-Glu6, p-amino Phe7]SP6-11 were all inactive. The relative activities of the other peptides were: [D-Phe7]SP1-11 (1.8) > [D-Pro2, D-Phe7, D-Trp9]SP1-11 (1.3) > SP1-11 (1.0) > SP1-9 (0.3) = SP1-8 (0.3) .gtoreq. ERP (0.2) > SP1-7 (0.04) > SP1-6 (0.006) = SP1-4 (0.006). Rat basophilic leukemia cells (RBL-2H3) fail to respond to SP at concentrations which activate rat mast cells. Release of 5-hydroxytryptamine by immunological activation of RBL cells is not changed by the presence of SP. The mechanism of action of SP on mast cells and the nature of the SP receptor on mast cells is discussed in relation to SP receptors in other cell types.