Madsen K M, Verlander J W, Tisher C C
Laboratory of Experimental Morphology, University of Florida College of Medicine, Gainesville 32610-0224.
J Electron Microsc Tech. 1988 Jun;9(2):187-208. doi: 10.1002/jemt.1060090206.
The relationship between structure and function in the distal tubule and collecting duct has been studied with morphologic and physiologic techniques, including morphometric analysis, to identify functionally distinct cell populations. The distal tubule, including the thick ascending limb (TAL) and the distal convoluted tubule (DCT), is involved in active reabsorption of sodium chloride. It is characterized by extensive invaginations of the basolateral plasma membrane, numerous mitochondria, and high Na-K-ATPase activity, features characteristic for an epithelium involved in active transport. Between the distal tubule and the collecting duct is a transition region, the connecting segment or the connecting tubule (CNT), which exhibits species differences with respect to both structure and function. The collecting duct includes the cortical (CCD), the outer medullary (OMCD), and the inner medullary (IMCD) collecting ducts. Principal cells are present throughout the collecting duct, whereas intercalated cells are located mainly in the CCD and OMCD. Morphometric analysis combined with micropuncture and microperfusion studies has provided evidence that the CNT and principal cells are responsible for potassium secretion in the connecting segment and the CCD. The OMCD is a main site of hydrogen ion secretion, and morphometric studies have provided evidence that the intercalated cells in this segment secrete hydrogen ion at least in the rat. Two configurations of intercalated cells exist in the CCD--a type A and a type B. The A cells are similar in ultrastructure to the intercalated cells in the OMCD and are believed to be involved in hydrogen ion secretion. The function of the B cells remains to be established. The inner two-thirds of the IMCD corresponds to the papillary collecting duct, which has a high permeability to urea. The relationship between structure and function in the IMCD has not been studied in detail. This review emphasizes the role of morphometric analysis in establishing the relationship between structure and function in the distal nephron.
运用形态学和生理学技术，包括形态计量分析，研究了远端小管和集合管的结构与功能之间的关系，以识别功能不同的细胞群。远端小管包括厚壁升支（TAL）和远端曲管（DCT），参与氯化钠的主动重吸收。其特征是基底外侧质膜广泛内陷、线粒体众多以及钠钾ATP酶活性高，这些都是参与主动转运的上皮细胞的特征。在远端小管和集合管之间是一个过渡区域，即连接段或连接小管（CNT），其在结构和功能方面均存在种属差异。集合管包括皮质集合管（CCD）、外髓集合管（OMCD）和内髓集合管（IMCD）。主细胞存在于整个集合管中，而闰细胞主要位于CCD和OMCD中。形态计量分析结合微穿刺和微灌注研究提供了证据，表明CNT和主细胞负责连接段和CCD中的钾分泌。OMCD是氢离子分泌的主要部位，形态计量研究提供了证据，表明该段的闰细胞至少在大鼠中分泌氢离子。CCD中存在两种闰细胞构型——A型和B型。A型细胞的超微结构与OMCD中的闰细胞相似，被认为参与氢离子分泌。B型细胞的功能尚待确定。IMCD的内三分之二对应于乳头集合管，其对尿素具有高通透性。IMCD的结构与功能之间的关系尚未得到详细研究。本综述强调了形态计量分析在确立远端肾单位结构与功能关系中的作用。
