TY - JOUR T1 - Tachykinin NK<sub>2</sub> Receptor and Functional Mechanisms in Human Colon: Changes with Indomethacin and in Diverticular Disease and Ulcerative Colitis JF - Journal of Pharmacology and Experimental Therapeutics JO - J Pharmacol Exp Ther SP - 170 LP - 178 DO - 10.1124/jpet.107.130385 VL - 324 IS - 1 AU - Elizabeth Burcher AU - Fei Shang AU - Fiona J. Warner AU - Qin Du AU - David Z. Lubowski AU - Denis W. King AU - Lu Liu Y1 - 2008/01/01 UR - http://jpet.aspetjournals.org/content/324/1/170.abstract N2 - Neurokinin A (NKA) is an important spasmogen in human colon. We examined inflammatory disease-related changes in the tachykinin NK2 receptor system in human sigmoid colon circular muscle, using functional, radioligand binding, and quantitative reverse transcription-polymerase chain reaction methods. In circular muscle strips, indomethacin enhanced contractile responses to NKA (p &lt; 0.01) and to the NK2 receptor-selective agonist [Lys5,MeLeu9,Nle10]-NKA(4–10) (p &lt; 0.05) in both normal and acute diverticular disease (DD) specimens, indicating NK2 receptor-mediated release of relaxant prostanoids. Contractile responses to both tachykinins were reduced in strips from DD (p &lt; 0.001) and ulcerative colitis (UC) (p &lt; 0.05) specimens. Responses to acetylcholine were no different in other strips from the same disease patients, demonstrating that the change in responsiveness to tachykinins in disease is specifically mediated by the NK2 receptor. In membranes from UC specimens, receptor affinity for 125I-NKA (median KD 0.91 nM, n = 16) was lower (p &lt; 0.01) than that in age-matched control specimens (KD 0.55 nM, n = 40), whereas KD (0.65 nM, n = 28) in DD was no different from control. No disease-related changes in receptor number (Bmax) were found (mean, 2.0–2.5 fmol/mg of wet weight tissue), suggesting that the reduced contractile responses in disease are not due to a loss of receptor number. Different mechanisms may account for the reduced contractility in DD compared with UC. A gender-related difference in receptor density was seen in controls, with Bmax lower in females (1.77 fmol/mg, n = 15) than in males (2.60 fmol/mg, n = 25, p = 0.01). In contrast, no gender-related differences were seen in NK2 receptor mRNA in control colonic muscle, indicating that the gender difference is a post-translational event. The American Society for Pharmacology and Experimental Therapeutics ER -