FLUID SECRETION BY GLOMERULAR RENAL TUBULES

在42,000种脊椎动物中，只有30种能产生无肾小球的尿液 过滤。在这些无球物种中，液体分泌被认为是 一种管状传输机制。肾小球的液体分泌 然而，小管被认为是微不足道的。初步研究 在山上进行。荒岛生物实验室对此提出质疑 流行的观念。肾小球冬季比目鱼的近端小管 经显微解剖分离和浸泡的美洲假单胞菌 林格氏溶液在没有灌流的情况下产生自己的管状液体 流明。尿液分泌率平均为每毫米管长27.1pl/min 并依赖于管周洗浴介质中是否存在氯化钠。 初级分泌液(298.9 mOsm/kg H2O)对血管有轻微的高渗 沐浴介质(290.5 mOsm/kg H2O)可能通过分泌物 镁和硫的运输分泌液中的主要离子是 摩尔/升，钠(152.4)，氯(155.4)，镁(25.3)，S(9.9) 电子探针(WDS)分析。体液分泌通常被观察到是 与肾小管的放射状收缩和肾小管的运动有关 小管腔内的纤毛。这份拨款申请提出了详细的 体液分泌的研究：驱动力和机制。 然后实验将重点放在分泌镁和S的机制上 运输。所有研究都将在分离的近端小管上进行。 预计这一结果将对我们的理解产生广泛的影响 1)近端肾小管跨上皮体积血流，2)近端 单价和二价离子的小管分泌转运，3)低渗 对海洋硬骨鱼的调控，可能还有4)脊椎动物的进化 肾功能。在肾小球近端观察到的液体分泌 比目鱼的小管是发育的中间阶段 无球系膜肾功能？还是体液分泌是人体的基本功能？ 高等脊椎动物中尚未发现的肾小球近端小管 因为液体吸收率高而被检测到？

From the 42,000 vertebrate species only 30 produce urine without glomerular filtration. In these aglomerular species fluid secretion is recognized as a tubular transport mechanism. Fluid secretion in glomerular renal tubules, however, is thought to be negligible. Preliminary studies conducted at the Mt. Desert Island Biological Laboratory question this popular notion. Proximal tubules from the glomerular winter flounder Pseudopleuronectes americanus, isolated by microdissectiona nd bathed in Ringer's solution generate their own tubular fluid without perfusion of the lumen. Rates of fluid secretion average 27.1 pl/min per mm tubule length and depend on the presence of NaCl in the peritubular bathing medium. Primary secreted fluid (298.9 mOsm/kg H2O) is slightly hyperosmotic to the bathing medium (290.5 mOsm/Kg H2O) presumably through the secretory transport of Mg and S. The principal ions in secreted fluid are in mmoles/liter, Na (152.4), Cl (155.4), Mg (25.3), and S (9.9) as measured by electron probe (WDS) analysis. Fluid secretion is often observed to be associated with radial constrictions of the tubule and the movement of cilia in the tubule lumen. This grant application proposes the detailed study of fluid secretion: its driving forces and its mechanisms. Experiments will then focus on the mechanism of secretory Mg and S transport. All studies will be conducted on isolated proximal tubules. The results are expected to have broad implications for our understanding of 1) transepithelial volume flow in renal proximal tubules, 2) proximal tubule secretory transport of monovalent and divalent ions, 3) hypo-osmotic regulation of marine teleosts, and possibly 4) the evolution of vertebrate kidney functions. Does fluid secretion as observed in glomerular proximal tubules of the flounder represent an intermediary stage in the development of aglomerular renal functions? Or is fluid secretion a basic function of glomerular proximal tubules which in higher vertebrates has not been detected because of high fluid absorption rates?