Weitzman R E, Kleeman C R
West J Med. 1979 Dec;131(6):486-515.
The renal reabsorption of water independent of solute is the result of the coordinated function of the collecting duct and the ascending limb of the loop of Henle. The unique juxtaposition of the ascending and descending portions of the loop of Henle and of the vasa recta permits the function of a counter-current multiplier system in which water is removed from the tubular lumen and reabsorbed into the circulation. The driving force for reabsorption is the osmotic gradient in the renal medulla which is dependent, in part, on chloride (followed by sodium) pumping from the thick ascending loop of Henle. Urea trapping is also thought to play an important role in the generation of a hypertonic medullary interstitium. Arginine vasopressin (AVP) acts by binding to receptors on the cell membrane and activating adenylate cyclase. This, inturn, results in the intracellular accumulation of cyclic adenosine monophosphate (AMP) which in some fashion abruptly increases the water permeability of the luminal membrane of cells in the collecting duct. As a consequence, water flows along an osmotic gradient out of the tubular lumen into the medullary interstitium. Diabetes insipidus is the clinical condition associated with either a deficiency of or a resistance to AVP. Central diabetes insipidus is due to diminished release of AVP following damage to either the neurosecretory nuclei or the pituitary stalk. Possible causes include idiopathic, familial, trauma, tumor, infection or vascular lesions. Patients present with polyuria, usually beginning over a period of a few days. The diagnosis is made by showing that urinary concentration is impaired after water restriction but that there is a good response to exogenous vasopressin therapy. Nephrogenic diabetes insipidus can be identified by a patient's lack of response to AVP. Nephrogenic diabetes insipidus is caused by a familial defect, although milder forms can be acquired as a result of various forms of renal disease. Central diabetes insipidus is eminently responsive to replacement therapy, particularly with dDAVP, a long lasting analogue of AVP. Nephrogenic diabetes insipidus is best treated with a combination of thiazide diuretics as well as a diet low in sodium and protein.
肾脏对水的独立于溶质的重吸收是集合管和髓袢升支协同作用的结果。髓袢升支和降支以及直小血管独特的并列排列使得逆流倍增系统发挥作用，在此系统中，水从肾小管管腔被移除并重新吸收进入血液循环。重吸收的驱动力是肾髓质中的渗透梯度，其部分依赖于从髓袢厚壁升支泵出的氯离子（随后是钠离子）。尿素潴留也被认为在高渗髓质间质的形成中起重要作用。精氨酸加压素（AVP）通过与细胞膜上的受体结合并激活腺苷酸环化酶来发挥作用。这进而导致细胞内环磷酸腺苷（AMP）的细胞内积累，AMP以某种方式突然增加集合管细胞管腔膜的水通透性。结果，水沿着渗透梯度从肾小管管腔流出进入髓质间质。尿崩症是与AVP缺乏或对其抵抗相关的临床病症。中枢性尿崩症是由于神经分泌核或垂体柄受损后AVP释放减少所致。可能的原因包括特发性、家族性、创伤、肿瘤、感染或血管病变。患者表现为多尿，通常在几天内开始。诊断通过显示限水后尿浓缩功能受损，但对外源性加压素治疗有良好反应来确定。肾性尿崩症可通过患者对AVP无反应来识别。肾性尿崩症由家族性缺陷引起，尽管较轻的形式可因各种形式的肾脏疾病而获得。中枢性尿崩症对替代治疗，特别是对dDAVP（一种长效的AVP类似物）反应良好。肾性尿崩症最好用噻嗪类利尿剂以及低钠和低蛋白饮食联合治疗。
