Dantzler W H
Department of Physiology, College of Medicine, University of Arizona, Tucson 85724.
Am J Physiol. 1989 Nov;257(5 Pt 2):R982-8. doi: 10.1152/ajpregu.1989.257.5.R982.
Net fluid absorption (Jv), cell volume, and cell membrane area have been studied in isolated, perfused snake (Thamnophis spp.) proximal tubules. With Na+ in both perfusate and bathing medium, Jv averages approximately 0.9 nl.min-1.mm-1. When choline replaces Na+ in perfusate, Jv nearly ceases. When choline also replaces Na+ in bathing medium, so that both solutions are identical, Jv returns to the control rate. The results are the same when tetramethylammonium replaces Na+, when sucrose replaces Na+ and the equivalent amount of Cl-, and when methyl sulfate replaces Cl- alone. However, when Li+ replaces Na+ in perfusate alone or in both perfusate and bathing medium, Jv is unchanged. Jv at control rates is isosmotic and can be partially inhibited by cold and cyanide. When choline replaces Na+ in perfusate and bathing medium, cell volume doubles, and intercellular space volume nearly quintuples. The areas of the lateral and apical cell membranes also approximately double, so that the surface area-to-volume ratio remains constant. These morphological changes in the absence of Na+ occur concomitantly with maintenance of Jv, suggesting that they may play a permissive role in such maintenance.
已对分离的、灌注的蛇（束带蛇属）近端小管中的净液体吸收（Jv）、细胞体积和细胞膜面积进行了研究。当灌注液和浴液中均含有Na⁺时，Jv平均约为0.9 nl·min⁻¹·mm⁻¹。当灌注液中的Na⁺被胆碱取代时，Jv几乎停止。当胆碱也取代浴液中的Na⁺，使两种溶液相同时，Jv恢复到对照速率。当四甲基铵取代Na⁺、蔗糖取代Na⁺和等量的Cl⁻以及甲基硫酸酯单独取代Cl⁻时，结果相同。然而，当单独在灌注液中或在灌注液和浴液中Li⁺取代Na⁺时，Jv不变。对照速率下的Jv是等渗的，可被低温和氰化物部分抑制。当灌注液和浴液中的Na⁺被胆碱取代时，细胞体积加倍，细胞间隙体积几乎增加到五倍。侧面和顶端细胞膜的面积也大约加倍，因此表面积与体积比保持恒定。在没有Na⁺的情况下，这些形态学变化与Jv的维持同时发生，表明它们可能在这种维持中起允许作用。
