Evidence of NK1 and NK2 Tachykinin Receptors and their Involvement in HistamineRelease in a Murine Mast Cell Line

摘要

Binding of 3H substance P (SP) and histamine release were examined using a clonedmouse mast cell line. SP binding was saturable and specific. In the presence of 30mM Na2SO4/50NM Tris buffer, SP interacted with two types of binding sites with Kd values of 0.3 and 40nM. High-affinity SP binding was blocked by the inclusion of 0.5uM of the NK1 receptor selective ligand septide in the binding mixture. Neurokinin A (NKA) evoked concentration-dependent histamine release. At concentrations in the nanomolar range, the NK1 preferring agonists SP, SP methylester and physalaemin evoked 5% net release of histamine, which was substantially less than the maximum effect of NKA (+37%) in the micromolar range. Pretreatment of the cells with the NK2 antagonist peptide A reduced NKA-induced histamine release. D-Arg1,D-Phe5,D-Trp7 9,Leull-substance P, a putative SP antagonist, also elicited histamine release in the micromolar range, apparently acting as an agonist at the NK2 site. Compound 48/80, N-terminal SP fragments, neurokinin B and the two selective NK2 receptor antagonists cyclo(Gln-Trp-Phe-(R)-ANC-2Leu-Met) (peptide A) and cyclo(Gln-Trp-Phe-Gly-Leu-Met) (peptide B) were ineffective. Although the results suggest the coexistence of functional NK1 and NK2 receptors, it appears that in this mast cell line neurokinin-induced histamine release is primarily mediated by the NK2 receptor, characterized biochemically as a low affinity binding site with a Kd value of 40 nM for SP. Histamine release, substance P, tachykinin receptors.