Tolvaptan as a tool in renal physiology
Tolvaptan as a tool in renal physiology
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DOI：
10.1152/ajprenal.00330.2013
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发表时间：
2014-02-01
影响因子：
4.2
通讯作者：
Knepper, Mark A.
中科院分区：
文献类型：
--
作者：
Miranda, Carlos A.;Lee, Jae Wook;Knepper, Mark A.
几十年来，Brattleboro大鼠一直是肾脏生理学的有用模型。由于加压素-神经垂体后叶素基因突变，这些动物表现出中枢性尿崩症（缺乏循环加压素）。通过输注V2-选择性加压素类似物1-脱氨基-8-D-精氨酸加压素（dDAVP），可在这些动物中评估V2受体介导的肾脏加压素作用。然而，美国的主要商业供应商已经停止生产，需要另一种可靠的啮齿动物V2受体介导的加压素作用的实验模型。我们设计了一个体内方案，以研究加压素的反应，在大鼠肾脏中使用渗透微泵加载托伐普坦，一种非肽竞争性抑制剂的加压素V2受体。托伐普坦输注大鼠的平均尿渗透压为2，000 mosmol/kgH（2）O。托伐普坦输注导致水通道蛋白-2（AQP 2）、水通道蛋白-3（AQP 3）、上皮钠通道β亚基（β-ENaC）和γ-ENaC的肾脏丰度大幅降低，这与输注溶剂与输注加压素的Brattleboro大鼠中观察到的差异相当。因此，我们得出结论，托伐普坦输注大鼠提供了一个额外的模型（除了dDAVP输注Brattleboro大鼠），用于评估肾脏中V2受体介导的加压素作用。我们还提供了大鼠内髓集合管悬浮液的辅助体外数据，表明托伐普坦可以阻断加压素对体外水通道AQP 2磷酸化的影响。具体而言，托伐普坦几乎完全抑制加压素增加AQP 2在Ser 256、Ser 264和Ser 269磷酸化的能力，同时强烈抑制加压素诱导的AQP 2在Ser 261磷酸化的降低。
For decades, the Brattleboro rat has been a useful model in kidney physiology. These animals manifest central diabetes insipidus (lack of circulating vasopressin) due to a mutation in the vasopressin-neurophysin gene. V2 receptor-mediated vasopressin actions in the kidney can be assessed in these animals by infusing the V2-selective vasopressin analog 1-desamino-8-D-arginine vasopressin (dDAVP). However, the major commercial supplier in the United States has ceased production, creating the need for another reliable experimental model of V2 receptor-mediated vasopressin action in rodents. We designed an in vivo protocol to investigate vasopressin responses in the rat kidney using osmotic minipumps loaded with tolvaptan, a nonpeptide competitive inhibitor of the vasopressin V2 receptor. Tolvaptan-infused rats had a mean urinary osmolality of 2,000 mosmol/kgH(2)O in vehicle-infused rats. The tolvaptan infusion produced large decreases in the renal abundance of aquaporin-2 (AQP2), aquaporin-3 (AQP3), the beta-subunit of the epithelial sodium channel (beta-ENaC), and gamma-ENaC that were comparable to the differences seen in vehicleinfused vs. vasopressin-infused Brattleboro rats. Thus we conclude that tolvaptan infusion in rats provides an additional model (besides dDAVP-infusion in the Brattleboro rat) for the assessment of V2 receptor-mediated vasopressin actions in the kidney. We also provide ancillary in vitro data in rat inner-medullary-collecting-duct suspensions showing that tolvaptan can block vasopressin's effects on phosphorylation of the water channel AQP2 in vitro. Specifically, tolvaptan almost completely inhibited the ability of vasopressin to increase AQP2 phosphorylation at Ser256, Ser264, and Ser269, while strongly inhibiting a vasopressin-induced decrease in AQP2 phosphorylation at Ser261.