Welling L W, Welling D J, Ochs T J
Am J Physiol. 1987 Aug;253(2 Pt 2):F290-8. doi: 10.1152/ajprenal.1987.253.2.F290.
Isolated, lumen-collapsed, proximal and distally occluded segments of rabbit S1 and S2 proximal tubule were equilibrated in isotonic NaCl or isosmotic raffinose medium and then exposed acutely to hypotonic or hypertonic raffinose or NaCl solution. The result was a water flux per millimeter tubule length, JVo, across the basolateral cell membranes and a consequent cell swelling or shrinkage that could be measured by a video technique in the initial 0.1 s or less after a change from steady state. The cell volume change was proportional to the applied osmolality difference, delta pi, and differed consistently with the solute employed. From the equation JVo/delta pi = sigma LpA, where sigma is the basolateral membrane reflection coefficient for the osmotic solute used and LpA is the membrane hydraulic conductivity per millimeter tubule length, and from the assumption that sigma raffinose = 1, sigma NaCl was obtained by dividing the JVo/delta pi values from the NaCl studies by those from the raffinose studies. For both S1 and S2 segments, sigma NaCl was found to be approximately 0.5. A similar value was obtained from the rate of cell shrinkage immediately after isosmolar exchange of raffinose for NaCl medium.
将兔近端小管S1和S2分离出的、管腔塌陷、近端和远端闭塞的节段，在等渗氯化钠或等渗棉子糖培养基中平衡，然后急性暴露于低渗或高渗棉子糖或氯化钠溶液中。结果是每毫米小管长度的水通量JVo，跨基底外侧细胞膜，随之而来的细胞肿胀或收缩可以在从稳态改变后的最初0.1秒或更短时间内通过视频技术测量。细胞体积变化与施加的渗透压差值Δπ成正比，并且因所用溶质的不同而始终不同。根据方程JVo/Δπ = σLpA，其中σ是所用渗透溶质的基底外侧膜反射系数，LpA是每毫米小管长度的膜水力传导率，并且假设棉子糖的σ = 1，通过将来自氯化钠研究的JVo/Δπ值除以来自棉子糖研究的JVo/Δπ值来获得氯化钠的σ。对于S1和S2节段，均发现氯化钠的σ约为0.5。在将棉子糖等渗交换为氯化钠培养基后立即从细胞收缩速率获得了类似的值。
