Presence of NK1 receptors on a mucosal-like mast cell line, RBL-2H3 cells

Reverse transcription - polymerase chain reaction of mRNA from rat RBL-2H3 cells yielded a 316 base pair band consistent with that predicted for the neurokinin-1 (NK1) receptor. Saturation and competition binding with I-125-labeled Bolton-Hunter substance P, substance P fragments, and a series of selective tachykinin receptor agonists and antagonists demonstrated that RBL-2H3 cells express high affinity binding sites for substance P on their surfaces with the kinetic and pharmacological properties of NK1 receptors. The pharmacology of these I-125-labeled substance P binding sites was (from most to least potent) [Sar(9), Met(O-2)(11)]substance P > substance P 4-11 much greater than GR82334 much greater than MEN 10,376. However, substance P 1-4, substance P 8-11, substance P 9-11, and [Trp(7),beta-Ala(8)]neurokinin A 4-10 failed to compete for binding. The metabolically stable NK1 receptor agonist, [Sar(9),Met(O-2)(11)] substance P, caused a 49% increase in 5-hydroxytryptamine release above basal levels. The results demonstrate the presence of functional NK1 receptors on RBL-2H3 cells, a mucosal-like mast cell line.