SOLUTE AND WATER TRANSPORT IN RENAL EPITHELIA

肾脏含有几种不同的上皮细胞， 功能，负责尿液的形成。我们正在研究 这些上皮细胞在调节水，尿素， 铵、碳酸氢盐、钠、钾和氯化物。总 一种方法是从肾脏解剖上皮细胞，并研究其 在体外发挥作用。使用数学方法对数据进行分析和整合 肾脏中的运输模型。皮层采集实验 大鼠的导管显示大部分的NaCl主动吸收是通过 噻嗪敏感的电中性转运途径，由 心钠素（ANF）。研究正在进行中，使用聚合酶 链反应在单个显微切割的大鼠肾单位片段，定位 沿着肾单位编码ANF的特异性mRNA 受体鸟苷酸环化酶蛋白。离体灌流小管研究 证明了加压素调节的尿素转运蛋白的存在， 大鼠内髓集合体的顶膜和基底外侧膜 管道。在初步研究中，该转运蛋白已在非洲爪蟾中表达， 用兔肾髓质mRNA注射卵母细胞 （与M。Hediger，Boston）.我们已经开发并验证了 高时间分辨荧光光谱法测定尿素转运 在灌流小管中。研究正在继续绘制NH3、NH4+和 碳酸氢盐渗透性沿着肾单位，长期目标是 了解酸碱排泄的调节机制， 肾脏产氨酶活性沿着 肾单位已经完成。

The kidney contains several distinct epithelia that, in their aggregate function, are responsible for formation of the urine. We are studying the roles of these epithelia in the regulation of the excretion of water, urea, ammonium, bicarbonate, sodium, potassium, and chloride. The general approach is to dissect the epithelia from the kidney and to study their functions in vitro. The data are analyzed and integrated using mathematical models of transport in the kidney. Experiments in the cortical collecting duct of rat showed a large fraction of active NaCl absorption occurs via a thiazide-sensitive electroneutral transport pathway which is regulated by atrial natriuretic factor (ANF). Studies are underway, using the polymerase chain reaction in single microdissected rat nephron segments, to localize along the nephron the specific mRNA that codes for the ANF receptor-guanylate cyclase protein. Isolated perfused tubule studies have demonstrated the presence of a vasopressin-regulated urea transporter in the apical and basolateral membranes of the rat inner medullary collecting duct. In preliminary studies, the transporter has been expressed in Xenopus oocytes by injecting them with mRNA from rabbit renal inner medulla (collaboration with M. Hediger, Boston). We have developed and validated a high time-resolution spectrofluorometric method to measure urea transport in perfused tubules. Studies are continuing to map the NH3, NH4+, and bicarbonate permeabilities along the nephron with a long term goal of understanding the mechanism by which acid-base excretion is regulated by the kidney. Mapping of the activities of ammoniagenic enzymes along the nephron have been completed.