Evidence of NK1 and NK2 Tachykinin Receptors and their Involvement in Histamine Release in a Murine Mast Cell Line
ARMY MEDICAL RESEARCH INST OF CHEMICAL DEFENSE ABERDEEN PROVING GROUND MD
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Binding of 3H substance P SP and histamine release were examined using a cloned mouse mast cell line. SP binding was saturable and specific. In the presence of 30mM Na2SO450NM 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 4880, N- terminal SP fragments, neurokinin B and the two selective NK2 receptor antagonists cycloGln-Trp-Phe-R-ANC-2Leu-Met peptide A and cycloGln-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.
- Anatomy and Physiology