Dantzler W H, Brokl O H, Nagle R B, Welling D J, Welling L W
Am J Physiol. 1986 Jul;251(1 Pt 2):F150-5. doi: 10.1152/ajprenal.1986.251.1.F150.
Snake (Thamnophis spp.) proximal renal tubules were perfused and bathed in vitro either with medium containing sodium or with medium in which the sodium was replaced with choline. Net fluid absorption was measured by changes in volume marker concentration, and cell volumes and cell membrane surface areas were measured by ultrastructural morphometric methods. Net fluid absorption did not differ significantly in the presence or absence of sodium. However, during the 20-25-min perfusion in the absence of sodium, significant morphological changes took place. The volume of the cells, doubled and the volume of the intercellular spaces nearly quintupled. The areas of the lateral and apical cell membranes approximately doubled, but their surface densities remained essentially constant. Therefore the larger cells in the absence of sodium had proportionally enlarged surface areas, so that the volume-to-surface area ratio remained constant. These morphological changes occurred concomitantly with the maintenance of net fluid absorption and might play a permissive role in such maintenance in the absence of sodium.
用含钠培养基或用胆碱取代钠的培养基在体外对蛇（束带蛇属）的近端肾小管进行灌注和浸泡。通过体积标记物浓度的变化来测量净液体吸收量，并用超微结构形态计量学方法测量细胞体积和细胞膜表面积。无论有无钠存在，净液体吸收量均无显著差异。然而，在无钠的情况下进行20 - 25分钟的灌注过程中，发生了显著的形态学变化。细胞体积增加了一倍，细胞间隙的体积几乎增加了五倍。细胞侧面和顶端细胞膜的面积大约增加了一倍，但它们的表面密度基本保持不变。因此，在无钠情况下较大的细胞具有成比例增大的表面积，从而使体积与表面积之比保持恒定。这些形态学变化与净液体吸收的维持同时发生，并且可能在无钠情况下对这种维持起允许作用。
