Cellular organization of urinary acidification.
Cellular organization of urinary acidification.
复制标题
尿液酸化的细胞组织。
DOI：
10.1152/ajprenal.1986.251.2.f173
复制
发表时间：
1986
期刊：
影响因子：
--
通讯作者：
Steinmetz,PR
中科院分区：
文献类型：
--
作者：
Steinmetz,PR
海龟膀胱含有活性钠吸收、产电质子分泌和碳酸氢盐分泌（与氯化物吸收耦合）的转运系统，这些系统在功能上是独立的，并发生在专门的上皮细胞中。改变细胞内酸碱状态的操作，如PCO 2的变化，通过添加或检索膜囊泡引起α型碳酸酐酶（CA）细胞顶膜面积的显著变化，但对转运钠的颗粒细胞没有影响。α-CA细胞的顶端细胞膜通过冷冻断裂含有特征性的杆状膜内颗粒（RSP），并且在其细胞质侧上被栓钉包被。CA细胞（β型）的亚群，其特征是顶端微绒毛，未能表现出顶端对CO2刺激的反应，并且在其顶端膜上没有显示RSPs或螺柱;相反，这些元素可以在基底外侧膜上显示。这些元素极性的逆转以及生理学证据表明，β型细胞负责碳酸氢盐的分泌。CO2刺激α-CA细胞分泌H+的结构-功能研究表明，分泌速率（JH）与顶膜面积和RSPs数量相关。RSPs代表跨膜通道阵列和螺柱代表H+泵的催化单元的观点得到定量考虑的支持，但仍有待证明。尿酸化不仅受H+泵数量变化的调节，还受H+泵本身固有特性的调节。对于给定的泵群体，JH由跨主动转运途径的Δ microH密切控制。
The turtle bladder contains transport systems for active sodium absorption, electrogenic proton secretion, and bicarbonate secretion (coupled to chloride absorption) that are functionally separate and occur in specialized epithelial cells. Maneuvers that alter the intracellular acid-base state, such as changes in PCO2, cause marked changes in the apical membrane area of alpha-type carbonic anhydrase (CA) cells by addition or retrieval of membrane vesicles but have no effect on the granular cells that transport sodium. The apical cell membrane of alpha-CA cells contains characteristic rod-shaped intramembrane particles (RSP) by freeze fracture and is coated on its cytoplasmic side with studs. A subpopulation of CA cells (beta-type), which is characterized by apical microvilli, fails to exhibit an apical response to CO2 stimulation and does not reveal RSPs or studs at its apical membranes; instead, these elements can be demonstrated at the basolateral membrane. The reversal in the polarity of these elements as well as physiological evidence suggest that beta-type cells are responsible for bicarbonate secretion. Structure-function studies of CO2 stimulation of H+ secretion by alpha-CA cells indicate that the secretion rate (JH) correlates with apical membrane area and numbers of RSPs. The view that RSPs represent arrays of transmembrane channels and that studs represent catalytic units of H+ pumps is supported by quantitative considerations but remains to be proven. Urinary acidification is regulated not only by changes in the number of H+ pumps but also by the intrinsic properties of the H+ pump itself. For a given pump population, JH is closely controlled by the delta microH across the active transport pathway.