Homaidan F R, Zhao L, Burakoff R
Division of Gastroenterology and Nutrition, Winthrop-University Hospital, Mineola, New York.
Am J Physiol. 1995 Feb;268(2 Pt 1):G270-5. doi: 10.1152/ajpgi.1995.268.2.G270.
The physiological effects of prostaglandins (PG) are mediated through their interactions with specific receptors on effector cells. In this study the properties of PGE2 receptors in the rabbit distal colon were examined. We report the presence of specific, saturable, and high-affinity binding sites of PGE2 of the EP2 subtype in isolated colonic crypts. Scatchard analysis revealed the presence of two binding sites with dissociation constants of 0.3 and 10.8 nM and corresponding maximum number of receptors of 15 and 134 fmol/10(6) cells. From competition experiments in the presence of guanosine 5'-O-(3-thiotriphosphate), PGE2 binding was decreased, suggesting that the receptor is coupled to a G protein. No PGE2 binding sites were detected in surface cells. Levels of adenosine 3',5'-cyclic monophosphate (cAMP) were measured in isolated epithelial cells after being exposed to different concentrations of PGE2. cAMP levels were significantly increased only in the crypt cells when exposed to PGE2. These data provide the first demonstration for the existence of PGE2 receptors on colonic crypt cells, which when activated lead to increased levels of cAMP.
前列腺素（PG）的生理效应是通过其与效应细胞上特定受体的相互作用介导的。在本研究中，对兔远端结肠中PGE2受体的特性进行了检测。我们报告在分离的结肠隐窝中存在EP2亚型的PGE2特异性、可饱和且高亲和力结合位点。Scatchard分析显示存在两个结合位点，解离常数分别为0.3和10.8 nM，相应的最大受体数量分别为15和134 fmol/10(6)细胞。在存在鸟苷5'-O-(3-硫代三磷酸)的情况下进行竞争实验，PGE2结合减少，表明该受体与G蛋白偶联。在表面细胞中未检测到PGE2结合位点。在分离的上皮细胞中，在暴露于不同浓度的PGE2后测量了3',5'-环磷酸腺苷（cAMP）水平。仅在隐窝细胞中暴露于PGE2时，cAMP水平显著升高。这些数据首次证明结肠隐窝细胞上存在PGE2受体，其激活后会导致cAMP水平升高。
