Identification of both NK1 and NK2 receptors in guinea-pig airways

Br J Pharmacol. 1993 Oct;110(2):693-700. doi: 10.1111/j.1476-5381.1993.tb13867.x.

Abstract

1. NK1 and NK2 receptors have been characterized in guinea-pig lung membrane preparations by use of [125I-Tyr8]-substance P and [125I]-neurokinin A binding assays in conjunction with tachykinin-receptor selective agonists ([Sar9Met(O2)11]substance P for NK1 and [beta Ala8]neurokinin A (4-10) for NK2) and antagonists (CP-99,994 for NK1 and SR48968 for NK2). 2. The presence of high affinity, G-protein-coupled NK1 receptors in guinea-pig lung parenchymal membranes has been confirmed. The rank order of affinity for competing tachykinins was as predicted for an NK1 receptor: substance P = [Sar9Met(O2)11]substance P > substance P-methyl ester = physalaemin > neurokinin A = neurokinin B >> [beta Ala8]neurokinin A (4-10). The novel NK1 antagonist CP-99,994 has a Ki of 0.4 nM at this NK1 site. 3. In order to characterize [125I]-neurokinin A binding to guinea-pig lung, the number of [125I]-neurokinin A specific binding sites was increased 3-4 fold by purification of the parenchymal membranes over discontinuous sucrose gradients. The rank order of affinity determined for NK1- and NK2-receptor agonists and antagonists in competition for these sites showed that the majority (80%) of [125I]-neurokinin A specific binding was also to the NK1 receptor. 4. Under conditions where the guinea-pig lung parenchymal NK1 receptor was fully occupied by a saturating concentration of either [Sar9Met(O2)11]substance P (1 microM) or CP-99,994 (2.7 microM), residual [125I]-neurokinin A specific binding was inhibited in a concentration-dependent manner by both [beta Ala8]neurokinin A and SR48968. This result shows that the NK2 receptor is also present in these preparations. 5. Similar studies using guinea-pig tracheal membranes demonstrated that [125I]-neurokinin A specific binding was composed of a NK1-receptor component (60%), inhibited by both [Sar9Met(02)11]substance P and CP-99,994, and a significant NK2-receptor component, inhibited by both [beta Ala 8]neurokinin A andSR48968.6. In summary, these data demonstrate that guinea-pig lung parenchyma and guinea-pig trachea express both NK1 and NK2 receptors.

MeSH terms

  • Animals
  • Benzamides / pharmacology
  • Chromatography, High Pressure Liquid
  • Guinea Pigs
  • In Vitro Techniques
  • Iodine Radioisotopes
  • Lung / drug effects
  • Lung / metabolism
  • Male
  • Neurokinin A / analogs & derivatives
  • Neurokinin A / antagonists & inhibitors
  • Neurokinin A / pharmacology
  • Neurokinin-1 Receptor Antagonists
  • Peptide Fragments / pharmacology
  • Piperidines / pharmacology
  • Radioligand Assay
  • Receptors, Neurokinin-1 / drug effects
  • Receptors, Neurokinin-1 / metabolism*
  • Receptors, Neurokinin-2 / antagonists & inhibitors
  • Receptors, Neurokinin-2 / drug effects
  • Receptors, Neurokinin-2 / metabolism*
  • Respiratory System / drug effects
  • Respiratory System / metabolism*
  • Substance P / analogs & derivatives
  • Substance P / pharmacology
  • Trachea / drug effects
  • Trachea / metabolism

Substances

  • Benzamides
  • Iodine Radioisotopes
  • Neurokinin-1 Receptor Antagonists
  • Peptide Fragments
  • Piperidines
  • Receptors, Neurokinin-1
  • Receptors, Neurokinin-2
  • substance P, Sar(9)-Met(O2)(11)-
  • neurokinin A (4-10), beta-Ala(8)-
  • 3-(2-methoxybenzylamino)-2-phenylpiperidine
  • Substance P
  • SR 48968
  • Neurokinin A