UREA TRANSPORT AND THE URINARY CONCENTRATING MECHANISM

乳头状表面上皮被认为起着重要的作用。 在尿液浓缩机制中的作用。我们进行了研究，以 确定该上皮细胞中存在哪些转运蛋白。乳头状结构 从兔肾表面解剖出表面上皮 乳头，并安装在灌注室中，允许两侧 单独灌流。细胞体积在25摄氏度时使用 计算机化的定量显微镜，允许连续测量 活组织的细胞体积。将哇巴因(0.1毫米)添加到 基底外侧上皮体积增加20%。这 去除根尖浴液中的氯化钠可完全抑制体积增加， 钠、氯或钾，但不是通过去除尿素。最低只有1 根尖浴中的纳米分子布美他尼完全抑制了 哇巴因引起细胞肿胀。急性心肌梗死后心尖渗透压变化 添加或去除氯化钠会引起细胞体积的变化 比单靠渗透水流动所能解释的要大。这 高反应可被布美他尼阻断，并可被 加压素。这些观察到的结果与 底侧膜上的Na-K-ATPase和对布美他尼敏感的， 顶膜上的加压素反应性Na-K-Cl共转运体。这些 结果与氯化钠的经皮转运是一致的 这种上皮细胞可以改变盆腔尿液的成分。

The papillary surface epithelium has been proposed to play an important role in the urinary concentrating mechanism. We undertook studies to determine what transporters are present in this epithelium. The papillary surface epithelium was dissected from the surface of the rabbit renal papilla and mounted in a perfusion chamber which allowed both sides to be perfused independently. Cell volume was measured at 25 degrees C using computerized quantitative microscopy which allows continuous measurement of cell volume of the living tissue. Addition of ouabain (0.1 mM) to the basolateral side of the epithelium induced a 20% volume increase. This volume increase was completely inhibited by removal of apical bath NaCl, sodium, chloride, or potassium, but not by removal of urea. As little as 1 nanomolar bumetanide in the apical bath completely inhibited the ouabain-induced cell swelling. Changes in apical osmolality resulting from the addition or removal of NaCl caused cell volume changes that were greater than could be accounted for by osmotic water flow alone. This hyper-response was blocked by bumetanide and was stimulated by vasopressin. These observations are consistent with the presence of Na-K-ATPase on the basolateral membrane and a bumetanide-sensitive, vasopressin-responsive Na-K-Cl cotransporter in the apical membrane. These results are consistent with transpithelial transport of sodium chloride by this epithelium which could modify the composition of the pelvic urine.