Maunsbach A B, Giebisch G H, Stanton B A
Am J Physiol. 1987 Sep;253(3 Pt 2):F582-7. doi: 10.1152/ajprenal.1987.253.3.F582.
In this study we investigated the ultrastructure of the proximal tubule during alterations in fluid flow to determine whether previously observed changes in solute and water reabsorption may be related to alterations in cell ultrastructure. In each kidney, two proximal tubules (S2 segments) were perfused simultaneously at 5 and 45 nl/min. Subsequently, cell ultrastructure of control and experimental tubules was examined by electron microscopy in combination with morphometry. Changes in flow rate greatly modified the geometry of the tubule epithelium. Enhanced flow increased luminal diameter and decreased cell height. The number of microvilli per square micrometer of luminal epithelial surface area decreased with increased flow rate from a control value of 42.5 to 35.5 at high flow. However, the total number of microvilli per millimeter tubule length did not change. Thus the distance between microvilli was dependent on flow rate and was estimated to be 621, 741, and 904 A in low flow, control, and high flow tubules, respectively. We suggest that increased flow rate, perhaps by altering transepithelial hydrostatic pressure gradients, leads to an increase in the distance between the microvilli and to other alterations in cellular ultrastructure that may contribute to the augmentation of solute and water reabsorption.
在本研究中，我们研究了液体流动改变期间近端小管的超微结构，以确定先前观察到的溶质和水重吸收变化是否可能与细胞超微结构的改变有关。在每个肾脏中，以5和45 nl/min的流速同时灌注两条近端小管（S2段）。随后，通过电子显微镜结合形态计量学检查对照小管和实验小管的细胞超微结构。流速的变化极大地改变了小管上皮的几何形状。流速增加使管腔直径增大，细胞高度降低。每平方微米管腔上皮表面积的微绒毛数量随着流速增加而减少，从对照值42.5降至高流速时的35.5。然而，每毫米小管长度的微绒毛总数没有变化。因此，微绒毛之间的距离取决于流速，在低流速、对照和高流速小管中分别估计为621、741和904埃。我们认为，流速增加可能通过改变跨上皮静水压力梯度，导致微绒毛之间的距离增加以及细胞超微结构的其他改变，这可能有助于溶质和水重吸收的增强。
