Ashkar Z M, Martial S, Isozaki T, Price S R, Sands J M
Department of Medicine, Emory University School of Medicine, Atlanta, Georgia 30322, USA.
Am J Physiol. 1995 Jun;268(6 Pt 2):F1218-23. doi: 10.1152/ajprenal.1995.268.6.F1218.
Feeding rats a low-protein (8%) diet (LPD) for 2 wk induces a facilitated urea transporter in rat initial inner medullary collecting ducts (IMCDs). To determine whether this is preceded by an increase in mRNA abundance, we designed degenerate polymerase chain reaction primers to the rabbit facilitated urea transporter (UT2; G. You, C. P. Smith, Y. Kanai, W.-S. Lee, M. Stelzner, and M. A. Hediger. Nature Lond. 365: 844-847, 1993) and amplified a 716-bp cDNA fragment to perform Northern analysis of the base or tip of rat inner medulla. In the base, the predominant transcript was a 2.9-kb band, which increased 55% after 1 wk on an LPD; there was no change in a 4-kb band. In the tip, the 4-kb band predominated, but neither band varied with an LPD. Next, we functionally characterized the induced urea transporter using microperfused initial IMCDs from rats fed an LPD for 2 wk. First, 100 pM arginine vasopressin (AVP) stimulated urea permeability (Purea); 10 nM AVP increased Purea further. Second, raising perfusate and bath osmolality to 690 mosmol/kgH2O (NaCl added) stimulated Purea; adding AVP (10 nM) increased Purea further. Third, thiourea reversibly inhibited AVP-stimulated Purea.(ABSTRACT TRUNCATED AT 250 WORDS)
给大鼠喂食低蛋白（8%）饮食（LPD）2周会在大鼠初始髓质内集合管（IMCDs）中诱导一种易化尿素转运体。为了确定这之前是否有mRNA丰度的增加，我们设计了针对兔易化尿素转运体（UT2；G. 尤、C. P. 史密斯、Y. 金井、W.-S. 李、M. 施特尔茨纳和M. A. 赫迪格。《自然》伦敦 365: 844 - 847, 1993）的简并聚合酶链反应引物，并扩增出一个716 bp的cDNA片段，以对大鼠髓质基部或顶端进行Northern分析。在基部，主要转录本是一条2.9 kb的条带，在LPD喂养1周后增加了55%；一条4 kb的条带没有变化。在顶端，4 kb的条带占主导，但两条带在LPD喂养时均无变化。接下来，我们使用从喂食LPD 2周的大鼠分离的微灌流初始IMCDs对诱导的尿素转运体进行功能表征。首先，100 pM精氨酸加压素（AVP）刺激尿素通透性（Purea）；10 nM AVP进一步增加Purea。其次，将灌流液和浴液渗透压提高到690 mosmol/kgH2O（添加NaCl）刺激Purea；添加AVP（10 nM）进一步增加Purea。第三，硫脲可逆性抑制AVP刺激的Purea。（摘要截断于250字）
