Kitazawa Takio, Maeda Yoshimi, Kaiya Hiroyuki
Department of Pharmacology, School of Veterinary Medicine, Rakuno Gakuen University, Ebetsu, Hokkaido 069-8501, Japan.
Regul Pept. 2009 Nov 27;158(1-3):132-42. doi: 10.1016/j.regpep.2009.07.005. Epub 2009 Jul 15.
We identified a growth hormone secretagogue-receptor (GHS-R) for ghrelin (GRLN) in the Japanese quail, and examined relationship between its receptor distribution and the effects of ghrelin on the gastrointestinal tract of the quail. GHS-R expression and GRLN-induced response were also investigated in the chicken and compared with quail. Several types of GHS-R, namely GHS-R1a-L, GHS-R1a-S, GHS-R1aV, GHS-R1b, GHS-R1bV and GHS-R1tv-like receptor, were identified in quail cerebellum cDNA. Amino acid sequence of quail GHS-R1a-L was 98% identical to that of chicken GHS-R1a. GHS-R1a mRNA was expressed heterogeneously in the quail gastrointestinal tract with a high expression level in the colon, moderate levels in the esophagus and crop, and low levels in the proventriculus, gizzard and small intestine. The region-specific expression pattern was almost the same as that in the chicken. Chicken and quail GRLN caused contraction in the crop, proventriculus and colon of both the quail and chicken, whereas the small intestine was less sensitive. However, the contractile efficacy was more potent in the chicken than in the quail. Chicken motilin (MTL), another gut peptide, structurally resemble to GRLN, caused marked contraction in the small intestine of both the quail and chicken, and the region-specific effect of MTL was opposite to that of GRLN. In conclusion, GRLN mainly induces the contractile responses of the upper and lower gastrointestinal tract and MTL stimulates motility of the middle intestine in both the quail and chicken. Regions in which GRLN acts were consistent with the distribution of GHS-R1a mRNA, but the contractile efficacy was different in the quail and chicken. These results suggest a species-specific contribution of GRLN in the regulation of avian gastrointestinal contractility.
我们在日本鹌鹑中鉴定出了胃饥饿素（GRLN）的生长激素促分泌素受体（GHS-R），并研究了其受体分布与胃饥饿素对鹌鹑胃肠道影响之间的关系。我们还在鸡中研究了GHS-R的表达及胃饥饿素诱导的反应，并与鹌鹑进行了比较。在鹌鹑小脑cDNA中鉴定出了几种类型的GHS-R，即GHS-R1a-L、GHS-R1a-S、GHS-R1aV、GHS-R1b、GHS-R1bV和GHS-R1tv样受体。鹌鹑GHS-R1a-L的氨基酸序列与鸡GHS-R1a的同源性为98%。GHS-R1a mRNA在鹌鹑胃肠道中呈异质性表达，在结肠中表达水平较高，在食管和嗉囊中表达水平中等，而在前胃、砂囊和小肠中表达水平较低。这种区域特异性表达模式与鸡的几乎相同。鸡和鹌鹑的胃饥饿素均可引起鹌鹑和鸡的嗉囊、前胃和结肠收缩，而小肠对此不太敏感。然而，鸡的收缩效力比鹌鹑更强。另一种肠道肽鸡胃动素（MTL）在结构上与胃饥饿素相似，可引起鹌鹑和鸡小肠的明显收缩，且MTL的区域特异性作用与胃饥饿素相反。总之，胃饥饿素主要诱导鹌鹑和鸡上、下胃肠道的收缩反应，而胃动素刺激中肠的运动。胃饥饿素发挥作用的区域与GHS-R1a mRNA的分布一致，但鹌鹑和鸡的收缩效力不同。这些结果表明胃饥饿素在调节禽类胃肠收缩性方面具有物种特异性作用。
