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

在筛选激素对兔离体皮层集合管的腔作用时，发现前列腺素E_2(PGE_2)对跨上皮电压(Vt)有明显的腔作用。因此，我们首先探讨腔内前列腺素E_2的作用。结果表明：1)瞬时超极化后，INM~1uM的PGE_2对Vt有去极化作用。2)前列腺素E_2引起的Vt改变是特异的，因为腔内作用在基底侧前列腺素E_2或腔内加压素的存在下被保留。4)当浴液中存在Na/K ATPase抑制剂哇巴因或腔中存在Na/K ATPase抑制剂阿米洛利而不是腔中K通道阻滞剂BA时，由发光体PGE2引起的Vt改变被取消，以及5)确实，腔内PGE2抑制了腔到浴的钠通量。6)腔内PGE2还适度地增强渗透水的通透性，PGE_2的腔内作用与我们已报道的腔后叶加压素在Vt变化模式、对哇巴因的反应以及对钠和水运输的影响方面是不同的。提示尿液中PGE_2的排泄对体内尿液的产生也有调节作用。回到以Vt为标记物的筛选Ccd中激素的体腔作用，我们发现催产素、缓激肽、多巴胺和肾上腺素具有体腔作用，而体腔血管紧张素II或腺苷是惰性的。我们现在正在描述这些激素的腔内作用，并探索巴索拉尔和腔后叶加压素和PGE2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.