COUNTERCURRENT MULTIPLICATION SYSTEM WITHOUT ACTIVE TRANSPORT IN INNER MEDULLA
COUNTERCURRENT MULTIPLICATION SYSTEM WITHOUT ACTIVE TRANSPORT IN INNER MEDULLA
复制标题
DOI：
10.1038/ki.1972.97
复制
发表时间：
1972-01-01
影响因子：
19.6
通讯作者：
RECTOR, FC
中科院分区：
文献类型：
--
作者：
KOKKO, JP;RECTOR, FC
延髓无主动转运的逆流增殖系统。本研究报告了一个模型的逆流乘法，其中的下降支的Henle（DLH）和薄的上升支的Henle（ALH）作为纯粹的被动平衡段。该模型主要是基于通过灌注离体兔肾单位段获得的运输特性。为了使这种被动平衡模型有效，应该存在以下节段性膜特征：薄的DLH，对溶质相对不渗透，但具有高渗透水渗透性（渗透水平衡使管腔内Na浓度升高至高于邻近管腔的水平）;瘦ALH，对NaCl的渗透性比尿素高，对水的渗透流相对不渗透（低渗液体可以通过允许比尿素流入更多的净NaCl扩散出来而被动地产生）;厚的ALH，相对不透水和溶质，具有主动向外NaCl转运的能力（形成低NaCl浓度的低渗液）;远端小管、皮质和外髓集合管，在存在和不存在加压素的情况下均不渗透尿素（腔内尿素通过水提取而升高至高浓度）;内髓质和乳头状集合管，尿素渗透（允许通过被动扩散向下化学浓度梯度产生高间质尿素浓度）。所提出的模型的显着特点是，由厚ALH（表示为高尿素浓度外髓CD凭借水提取）主动向外NaCl运输所产生的能量被传输到乳头（尿素扩散的方式下，其浓度梯度）。反过来，乳头状间质尿素从DLH中提取水，产生高的腔内NaCl浓度，这允许整个系统通过NaCl从薄ALH中被动扩散而运行。通过该模型，在不使质量平衡方程失效的情况下，得到了所观察到的髓内浓度梯度。这一工作决定了一种在DHL下游分支机构中逆时针方向的倍增模式，而在Henlé上游分支机构中，这一部分主要是由被动平衡段组成的。该模型扩大了兔肾孤立节段体外灌注的运输障碍特征。为了这个模特
Countercurrent multiplication system without active transport in inaer medulla. The present study reports a model for counter-current multiplication in which both the descending limb of Henle (DLH) and thin ascending limb of Henle (ALH) operate as purely passive equilibrating segments. This model is based largely on transport characteristics obtained by perfusing isolated segments of rabbit nephrons in vitro. For this passive equilibration model to be operative the following segmental membrane characteristics should be present: thin DLH, relatively impermeant to solute but having high osmotic water permeability (osmotic water equilibration raises intraluminal Na concentration to higher levels than adjacent interstitium); thin ALH, more permeant to NaC1 than urea and relatively impermeant to osmotic flow of water (hypoosmolal fluid can be generated passively by allowing more net NaC1 to diffuse out than influx of urea); thick ALH, relativly water and solute impermeable with capacity of active outward NaCi transport (hypotonic fluid with a low NaC1 concentration is developed); distal tubule, cor-tical and outer medullary collecting duct, impermeant to urea both in presence and absence of vasopressin (intraluminal urea is raised to high concentrations by virtue of water abstraction); inner medulla and papillary collecting duct, urea permeant (allows for generation of high interstitial urea concentration by passive diffusion down chemical concentration gradient). The salient feature of the proposed model is that the energy generated by active outward NaCi transport by thick ALH (expressed as high urea concentration in outer medullary CD by virtue of water abstraction) is transmitted to the papilla (by way of urea diffusing down its concentration gradient). In turn, papillary interstitial urea abstracts water out of DLH generating high intraluminal NaCi concentrations which allows the entire system to operate by passive diffusion of NaCl out of the thin ALH. By this model, the observed medullary concentration gradients are developed without invalidating the mass balance equations.Système de multiplication par contre courant sans transport actif dans la médullaire interne. Ce travail décrit un modéle de multiplication par contre courant dans lequel la branche descendante (DHL) et Ia partie gréle de la branche ascendante de l'anse de Henlé (AHL) se comportent comme des segments d'dquili-bration passive. Ce modéle est largement fondé sur les caractéristiques de transport obtenues par Ia perfusion in vitro de segments isolés de néphrons de lapin. Pour que ce modéle