Adrenergic activation of electrogenic K+ secretion in guinea pig distal colonic epithelium: involvement of beta1- and beta2-adrenergic receptors.
Adrenergic activation of electrogenic K+ secretion in guinea pig distal colonic epithelium: involvement of beta1- and beta2-adrenergic receptors.
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DOI：
10.1152/ajpgi.00076.2009
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发表时间：
2009-05
期刊：
影响因子：
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通讯作者：
Jin Zhang;S. Halm;D. Halm
中科院分区：
文献类型：
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作者：
Jin Zhang;S. Halm;D. Halm
肾上腺素能刺激豚鼠远端结肠离体粘膜的生电性K+分泌需要激活两种β-肾上腺素能受体亚型（β-AdrR）。在Ussing腔的粘膜浴液中加入肾上腺素（epi）或去甲肾上腺素（norepi）可增加短路电流（Isc）和跨上皮电导（Gt），这与阳离子分泌一致。β-肾上腺素能分类得到了普萘洛尔对这种分泌反应的拮抗作用以及α-AdrR拮抗剂BE 2254（α 1-AdrR）和育亨宾（α 2-AdrR）缺乏作用的支持。亚型选择性拮抗剂CGP 20712 A（β 1-AdrR）、ICI-118551（β 2-AdrR）和SR 59320 A（β 3-AdrR）在抑制epi刺激的Isc反应方面相对无效。CGP 20712 A和ICI-118551联合抑制了该反应，这支持了β 1-AdrR和β 2-AdrR的协同作用。通过RT-PCR检测结肠上皮细胞的RNA，显示β 1-AdrR和β 2-AdrR的mRNA表达。通过免疫印迹显示分子量与单体和寡聚体一致的条带来指示蛋白质表达。β 1-AdrR和β 2-AdrR的免疫反应性（ir）在Lieberkühn隐窝柱状上皮细胞的基底外侧膜以及隐窝间表面上皮中显著。胞膜鞘中的细胞也有β 1-AdrR（ir），但没有可辨别的β 2-AdrR（ir）。通过Isc和Gt测量的K+分泌的肾上腺素能敏感性相对较低，如epi的EC（50）为41 +/- 7 nM和norepi的EC（50）为50 +/- 14 nM所示。肾上腺素能激活产电K+分泌需要β 1-AdrR和β 2-AdrR的参与，与任一受体亚型的报告值相比，激动剂敏感性降低。
Adrenergic stimulation of electrogenic K+ secretion in isolated mucosa from guinea pig distal colon required activation of two beta-adrenergic receptor subtypes (beta-AdrR). Addition of epinephrine (epi) or norepinephrine (norepi) to the bathing solution of mucosae in Ussing chambers increased short-circuit current (Isc) and transepithelial conductance (Gt), consistent with this cation secretion. A beta-adrenergic classification was supported by propranolol antagonism of this secretory response and the lack of effect by the alpha-AdrR antagonists BE2254 (alpha1-AdrR) and yohimbine (alpha2-AdrR). Subtype-selective antagonists CGP20712A (beta1-AdrR), ICI-118551 (beta2-AdrR), and SR59320A (beta3-AdrR) were relatively ineffective at inhibiting the epi-stimulated Isc response. In combination, CGP20712A and ICI-118551 inhibited the response, which supported a synergistic action by beta1-AdrR and beta2-AdrR. Expression of mRNA for both beta1-AdrR and beta2-AdrR was indicated by RT-PCR of RNA from colonic epithelial cells. Protein expression was indicated by immunoblot showing bands at molecular weights consistent with monomers and oligomers. Immunoreactivity (ir) for beta1-AdrR and beta2-AdrR was prominent in basolateral membranes of columnar epithelial cells in the crypts of Lieberkühn as well as intercrypt surface epithelium. Cells in the pericryptal sheath also had beta1-AdrR(ir) but did not have discernable beta2-AdrR(ir). The adrenergic sensitivity of K+ secretion measured by Isc and Gt was relatively low as indicated by EC(50)s of 41 +/- 7 nM for epi and 50 +/- 14 nM for norepi. Adrenergic activation of electrogenic K+ secretion required the involvement of both beta1-AdrR and beta2-AdrR, occurring with an agonist sensitivity reduced compared with reported values for either receptor subtype.