Vergnolle N, Macnaughton W K, Al-Ani B, Saifeddine M, Wallace J L, Hollenberg M D
Gastrointestinal, University of Calgary Faculty of Medicine, 3330 Hospital Drive NW, Calgary, Alberta Canada T2N4N1.
Proc Natl Acad Sci U S A. 1998 Jun 23;95(13):7766-71. doi: 10.1073/pnas.95.13.7766.
The effects of PAR2-activating PAR2-activating peptides, SLIGRL (SL)-NH2, and trans-cinnamoyl-LIGRLO (tc)-NH2 were compared with the action of trypsin, thrombin, and the PAR1 selective-activating peptide: Ala-parafluoroPhe-Arg-cyclohexylAla-Citrulline-Tyr (Cit)-NH2 for stimulating intestinal ion transport. These agonists were added to the serosa of stripped rat jejunum segments mounted in Ussing chambers, and short circuit current (Isc) was used to monitor active ion transport. The relative potencies of these agonists also were evaluated in two bioassays specific for the activation of rat PAR2: a cloned rat PAR2 cell calcium-signaling assay (PAR2-KNRK cells) and an aorta ring relaxation (AR) assay. In the Isc assay, all agonists, except thrombin, induced an Isc increase. The SL-NH2-induced Isc changes were blocked by indomethacin but not by tetrodotoxin. The relative potencies of the agonists in the Isc assay (trypsin>>SL-NH2>tc-NH2>Cit-NH2) were strikingly different from their relative potencies in the cloned PAR2-KNRK cell calcium assay (trypsin>>>tc-NH2 congruent with SL-NH2>>>Cit-NH2) and in the AR assay (trypsin>>>tc-NH2 congruent with SL-NH2). Furthermore, all agonists were maximally active in the PAR2-KNRK cell and AR assays at concentrations that were one (PAR2 -activating peptides) or two (trypsin) orders of magnitude lower than those required to activate intestinal transport. Based on the distinct potency profile for these agonists and the considerable differences in the concentration ranges required to induce an Isc effect in the intestinal assay compared with the PAR2-KNRK and AR assays, we conclude that a proteinase-activated receptor, pharmacologically distinct from PAR2 and PAR1, is present in rat jejunum and regulates intestinal transport via a prostanoid-mediated mechanism.
将PAR2激活肽SLIGRL（SL）-NH2和反式肉桂酰-LIGRLO（tc）-NH2的作用与胰蛋白酶、凝血酶以及PAR1选择性激活肽Ala-对氟苯丙氨酸-精氨酸-环己基丙氨酸-瓜氨酸-酪氨酸（Cit）-NH2刺激肠道离子转运的作用进行了比较。将这些激动剂添加到安装在尤斯灌流小室中的剥离大鼠空肠段的浆膜侧，并用短路电流（Isc）监测主动离子转运。还在两种针对大鼠PAR2激活的生物测定中评估了这些激动剂的相对效力：克隆的大鼠PAR2细胞钙信号测定（PAR2-KNRK细胞）和主动脉环舒张（AR）测定。在Isc测定中，除凝血酶外，所有激动剂均诱导Isc增加。吲哚美辛可阻断SL-NH2诱导的Isc变化，但河豚毒素不能。激动剂在Isc测定中的相对效力（胰蛋白酶>>SL-NH2>tc-NH2>Cit-NH2）与其在克隆的PAR2-KNRK细胞钙测定（胰蛋白酶>>>tc-NH2与SL-NH2相当>>>Cit-NH2）和AR测定（胰蛋白酶>>>tc-NH2与SL-NH2相当）中的相对效力显著不同。此外，所有激动剂在PAR2-KNRK细胞和AR测定中的最大活性浓度比激活肠道转运所需的浓度低一个（PAR2激活肽）或两个（胰蛋白酶）数量级。基于这些激动剂不同的效力谱以及与PAR2-KNRK和AR测定相比，在肠道测定中诱导Isc效应所需的浓度范围存在显著差异，我们得出结论，大鼠空肠中存在一种与PAR2和PAR1在药理学上不同的蛋白酶激活受体，其通过类前列腺素介导的机制调节肠道转运。
