Participation of luminal actions of hormones in the distal renal tubules in regulation of renal function

在离体兔皮质集合管（CCD）的激素管腔效应研究中，发现前列腺素E_2（PGE_2）对跨上皮电压（Vt）有明显的管腔效应。结果表明：1）1 μ M至1 μ M的前列腺素E_2可使心室肌在短暂超极化后去极化。2)由于在基底外侧PGE 2或管腔加压素存在下管腔作用得以保留，因此由管腔PGE 2诱导的Vt变化是特异性的。3)此外，当给予基底侧时，模拟PGE 2作用的前列腺素12不能诱导管腔侧的Vt变化。4）在浴中存在Na/K ATP酶抑制剂哇巴因或管腔中存在Na通道阻断剂阿米洛利的情况下，管腔中存在PGE 2诱导的Vt变化被消除，但不被管腔中的K通道阻断剂Ba消除，以及5）事实上，6）管腔内PGE_2也适度地增加渗透水的通透性，因此，在Vt变化模式、对哇巴因的反应以及对Na和水转运的影响方面，PGE_2的管腔作用不同于我们已经报道的管腔内加压素。回到以Vt为标记筛选CCD中激素的管腔作用，我们发现催产素、缓激肽、多巴胺和肾上腺素具有管腔作用，而管腔血管紧张素II或腺苷则无管腔作用。我们现在正在对这些激素的管腔作用进行表征，并探索基底层和管腔加压素与PGE 2之间的相互作用。

In screening the luminal action of hormones in isolated perused rabbit cortical collecting duct (CCD), distinct luminal action of prostaglandin E2 (PGE2) on transepithelial voltage (Vt) was found. Thus, we first addressed to exploration of the effect of luminal PGE2. As the results : 1) InM to 1muM luminalPGE2 depolarizes Vt after transient hyperpolarization. 2) the Vt change induced by luinal PGE2 is specific, since the luminal action is preserved in the presence of basolateral PGE2, or luminal vasopressin. 3) Furthermore, prostaglandin 12 which mimic the action of PGE2 when administered to the basolateral side fails to induce a Vt change from the luminal side.4) the luminla PGE2-induced Vt change is abolished in the presence of the Na/K ATPase inhibitor ouabain in the bath or the Na channel blocker amiloride in the lumen but not by the K channel blocker Ba in the lumen, and 5) indeed, the lumen-to-bath Na flux is suppressed by luminal PGE2,6) luminal PGE2 also enhances osmotic water permeability to a modest degree.Taken together, the lumnal action of PGE2 is distinct from that of luminal vasopressin which we have alredy reported in terms of the pattern of Vt change, response to ouabain, and effect on Na and water transport. It is suggested that PGE2 excreted in the urine also regulate the urine production in vivo.Coming back to the screening of luminal action so fo hormones in the CCD using Vt as the marker, we next found that oxytocine, bradykinin, dopamine and adrenalin have luminal action swhile luminal angiotensin II or adenosine are inert. We are now in the process of characterization of the luminal actions of these hormones and exploratioin of the interactions between basolateal and luminal vasopressin and PGE2.