Structure of the nephron and sites of action of hormones with special reference to hydro-mineral metabolism in the kidney of the bullfrog.

本研究旨在阐明牛蛙肾脏中各种激素沿肾单位的作用部位。这些激素分别是精氨酸催产素（AVT）、中叶催产素（MST）和甲状旁腺激素（PTH）。在此基础上，用光镜和电镜对牛蛙肾脏进行了形态学观察，并对牛蛙肾脏的连续切片进行了肾元重建。然后，我使用了一种微技术，该技术允许在含有局部小管的样品中测量激素依赖性腺苷酸环化酶的活性，这些小管是通过显微解剖从胶原酶处理的肾组织中分离出来的。每个肾元由以下部分组成：肾小体、纤毛颈段、近端小管、纤毛中间段、远端小管、连接小管、集管。早期远端小管和连接小管的细胞超微结构分别与哺乳动物的厚升肢和皮质集束小管相似。方法：在肾细胞的微解剖片段中检测细胞对激素的反应产生cAMP。(1) AVT：不同节段（肾小体、近端、远端及连接小管）cAMP基础水平无显著差异。春季的基础含量高于晚秋。当AVT （1mum）加入到培养培养基中时，AVT激活远端和连接小管中cAMP的产生，但不激活肾小体和近端小管。然而，在深秋收集的青蛙的早期远端小管中没有观察到明显的AVT反应。这些结果表明v_2型受体可能存在于牛蛙肾的远端和连接小管中。牛蛙肾单位对AVT的反应性可能存在季节差异。(2)甲状旁腺素：甲状旁腺素对两组小鼠cAMP的形成均无刺激作用。近端和远端小管。在两段小管中观察到的cAMP形成缺乏激素刺激可能反映了这些制剂中完全缺乏与cAMP生成系统相关的激素受体，它们的存在量非常小，或者本研究中使用的方法无法检测到它们。(3) MST和降钙素：由于这些激素的研究正在进行中，没有足够的数据来得出结论。少

The present study was projected to elucidate the sites of action for various hormones along the nephrons in the kidney of the bullfrog. Those hormones are arginine vasotocin (AVT), mesotocin (MST) and parathyroid hormone (PTH). On the basis of this study, morphological observation of the kidney was examined by light and electron microscopy and the reconstruction of the nephron was obtained from a serial section of the kidney of a bullfrog. Then, I used a microtechnique that allows hormone-dependent adenylate cyclase activity to be measured in samples containing a localized piece of tubules isolated by microdissection from collagenase-treated kidney tissue.1. MorphologyEach nephron consists of the following parts : renal corpuscle, ciliated neck segment, proximal tubule, ciliated intermediate segment, distal tubule, connecting tubule, and collecting duct. The cellular ultrastructures of the early distal and the connecting tubules have resemblance to those of the mammalian thick ascendin … More g limb and of the cortical collecting tubule, respectively.2. MethodologyCellular production of cAMP in response to hormone was examined in microdissected segments of the nephron.3. Effects of Hormones(1) AVT : The basal levels of cAMP were not significantly different among the segments (renal corpuscle, proximal, distal and connecting tubules). However, the basal levels were higher in spring than in late autumn. When AVT (1 muM) was added to the incubation medium, AVT activated the production of cAMP in both distal and connecting tubules but not in the renal corpuscle and proximal tubule. However, no appreciable responses to AVT were observed in the early distal tubules from frogs collected in late autumn. These results suggest that V_2-type receptors may be present in both distal and connecting tubules of the bullfrog kidney. Seasonal differences may exist with respect to the responsiveness to AVT of the nephrons of the bullfrog.(2) PTH : There was no stimulation of cAMP formation by PTH in both. the proximal and the distall tubules. The lack of hormonal stimulation of cAMP formation observed in both segments of tubules might reflect either the total absence of hormonal receptors associated either a cAMP-generating system in these preparations, their presence in only very small quantity, or the fact that they are not detectable by the methods used in this study.(3) MST and calcitonin : As study of these hormones is now being carried out, enough data to get conclusion are not available. Less