Di Sole Francesca, Cerull Robert, Babich Victor, Casavola Valeria, Helmle-Roth Corinna, Burckhardt Gerhard
Department of Physiology and Pathophysiology, University of Göttingen, Göttingen, Germany.
J Cell Physiol. 2008 Jul;216(1):221-33. doi: 10.1002/jcp.21399.
The renal function of the A(3) adenosine receptor (A3AR) is poorly characterized. In this study, we report that the A3AR-selective agonist, 1-[2-chloro-6-[[(3-iodophenyl)methyl]amino]-9H-purine-9-yl]-1-deoxy-N-methyl-b-D-ribofuranuronamide (2-Cl-IBMECA) regulates the Na+/H+ exchanger-3 (NHE3) in a dose- and time-dependent fashion. In opossum kidney (OK) cells, 2-Cl-IBMECA at high (10(-6) M) and low (10(-8) M) dose inhibits NHE3 by a multiphasic time course with an acute phase of NHE3 inhibition from 15 min to 1 h, followed by a chronic phase of NHE3 inhibition from 24 to 48 h. Pre-incubation with either the selective A3AR-antagonist MRS1523 (10(-7) M) or the protein kinase C inhibitor, Calphostin C (10(-8) M) completely blocked 10(-6) M 2-Cl-IBMECA-induced acute (15 min) and chronic (24 h) phases of NHE3 inhibition. In contrast, the acute inhibitory phase (15 min) of 10(-8) M 2-Cl-IBMECA was completely prevented only when Calphostin C (10(-8) M) was added in conjunction with the protein kinase A inhibitor, H89 (10(-7) M). Acute (15 or 30 min depending on the A3AR-agonist concentration) A3AR-dependent inhibition of NHE3 activity was accompanied by decrease in cell surface NHE3 protein with no change in total NHE3 antigen. Chronic (24 h) A3AR-mediated down-regulation of NHE3 was associated with reduction of surface NHE3, decreased total NHE3 protein (70%) and a paradoxical rise of NHE3 RNA (40%). In summary, these results indicate that A3AR directly regulates NHE3 at multiple levels in a complex pattern. A3AR-dependent short- and long-term inhibition of NHE3 may be a fundamental mechanism of net sodium and fluid balance.
A(3) 腺苷受体（A3AR）的肾功能特性尚不明确。在本研究中，我们报告A3AR选择性激动剂1-[2-氯-6-[[(3-碘苯基)甲基]氨基]-9H-嘌呤-9-基]-1-脱氧-N-甲基-β-D-呋喃核糖酰胺（2-Cl-IBMECA）以剂量和时间依赖性方式调节钠/氢交换体3（NHE3）。在负鼠肾（OK）细胞中，高剂量（10(-6) M）和低剂量（10(-8) M）的2-Cl-IBMECA通过多相时间过程抑制NHE3，NHE3抑制的急性期为15分钟至1小时，随后是24至48小时的慢性期。用选择性A3AR拮抗剂MRS1523（10(-7) M）或蛋白激酶C抑制剂Calphostin C（10(-8) M）预孵育可完全阻断10(-6) M 2-Cl-IBMECA诱导的NHE3抑制的急性（15分钟）和慢性（24小时）期。相比之下，仅当Calphostin C（10(-8) M）与蛋白激酶A抑制剂H89（10(-7) M）联合添加时，才能完全阻止10(-8) M 2-Cl-IBMECA的急性抑制期（15分钟）。急性（15或30分钟，取决于A3AR激动剂浓度）A3AR依赖性NHE3活性抑制伴随着细胞表面NHE3蛋白减少，而总NHE3抗原无变化。慢性（24小时）A3AR介导的NHE3下调与表面NHE3减少、总NHE3蛋白减少（70%）以及NHE RNA矛盾性升高（40%）有关。总之，这些结果表明A3AR以复杂模式在多个水平直接调节NHE3。A3AR依赖性NHE3的短期和长期抑制可能是钠和液体净平衡的基本机制。
