Von Schrenck T, Heinz-Erian P, Moran T, Mantey S A, Gardner J D, Jensen R T
Digestive Diseases Branch, National Institute of Diabetes and Digestive and Kidney Diseases, Bethesda 20892.
Am J Physiol. 1989 Apr;256(4 Pt 1):G747-58. doi: 10.1152/ajpgi.1989.256.4.G747.
To identify receptors for bombesin-related peptides in the rat esophagus, we measured binding of 125I-Bolton-Hunter neuromedin B (125I-BH-neuromedin B) and 125I-[Tyr4]bombesin to tissue sections from the rat esophagus and compared the results with those for rat pancreas. Esophagus bound both tracers, whereas pancreas bound only 125I-[Tyr4]bombesin. In each tissue binding was saturable, dependent on pH, on time, and on temperature, reversible, and specific. Autoradiography demonstrated binding of both tracers only to the muscularis mucosae of the esophagus and binding of 125I-[Tyr4]bombesin diffusely over pancreatic acini. In the esophagus, the relative potencies for inhibition of binding of both tracers were as follows: neuromedin B greater than bombesin greater than GRP = neuromedin C; similar relative potencies were found for causing contraction of muscle strips from whole esophagus and from the isolated muscularis mucosae. In pancreas tissue sections and dispersed acini, the relative potencies for inhibition of binding of 125I-[Tyr4]bombesin were as follows: bombesin greater than GRP = neuromedin C much greater than neuromedin B. Similar relative potencies were found for stimulation of enzyme secretion from dispersed pancreatic acini. Computer analysis in both tissues demonstrated only a single binding site. The present study demonstrates that rat esophagus muscle possesses specific receptors for bombesin-related peptides. Furthermore, this study shows that the esophageal bombesin receptors represent a previously unidentified class of bombesin receptors in that they have a higher affinity for neuromedin B than for bombesin. In contrast, the pancreatic bombesin receptors have, like all other bombesin receptors described to date, a high affinity for bombesin, but low affinity for neuromedin B.
为了鉴定大鼠食管中蛙皮素相关肽的受体，我们测定了¹²⁵I-博尔顿-亨特神经降压素B（¹²⁵I-BH-神经降压素B）和¹²⁵I-[酪氨酸⁴]蛙皮素与大鼠食管组织切片的结合，并将结果与大鼠胰腺的结果进行比较。食管结合了两种示踪剂，而胰腺仅结合¹²⁵I-[酪氨酸⁴]蛙皮素。在每个组织中，结合是可饱和的，依赖于pH、时间和温度，是可逆的且具有特异性。放射自显影显示两种示踪剂仅与食管的黏膜肌层结合，¹²⁵I-[酪氨酸⁴]蛙皮素在胰腺腺泡上呈弥漫性结合。在食管中，抑制两种示踪剂结合的相对效力如下：神经降压素B＞蛙皮素＞胃泌素释放肽=神经降压素C；在引起整个食管和分离的黏膜肌层肌肉条收缩方面也发现了类似的相对效力。在胰腺组织切片和分散的腺泡中，抑制¹²⁵I-[酪氨酸⁴]蛙皮素结合的相对效力如下：蛙皮素＞胃泌素释放肽=神经降压素C＞＞神经降压素B。在刺激分散的胰腺腺泡分泌酶方面也发现了类似的相对效力。两种组织的计算机分析均仅显示一个结合位点。本研究表明大鼠食管肌肉具有蛙皮素相关肽的特异性受体。此外，本研究表明食管蛙皮素受体代表了一类先前未鉴定的蛙皮素受体，因为它们对神经降压素B的亲和力高于对蛙皮素的亲和力。相反，胰腺蛙皮素受体与迄今描述的所有其他蛙皮素受体一样，对蛙皮素具有高亲和力，但对神经降压素B具有低亲和力。
