Bergeron L J, Stever A J, Light D B
Department of Biology, Ripon College, Wisconsin 54971, USA.
Am J Physiol. 1996 Apr;270(4 Pt 2):R801-10. doi: 10.1152/ajpregu.1996.270.4.R801.
The cellular basis of regulatory volume decrease (RVD) by mudpuppy (Necturus maculosus) red blood cells (RBCs) was examined. Volume regulation was inhibited by replacing extracellular Na+ with K+. In contrast, addition of gramicidin (5 microM) to the extracellular medium enhanced RVD. The K(+)-channel blocker quinine (1 mM) also inhibited RVD, and this inhibition was reversed by gramicidin (5 microM). In addition, a 0 Ca(2+)-EGTA Ringer blocked RVD, whereas the Ca2+ ionophore A23187 ( microM) enhanced recovery of cell volume. The stretch-activated ion channel antagonist gadolinium (10 microM) inhibited RVD, and this effect was reversed by A23187 (2 microM). Furthermore, the calmodulin inhibitors pimozide (10 microM) and N-(6-aminohexyl)-5-chloro-1-napthalene-sulfonamide (0.1 mM) blocked RVD, and this inhibition was reversed with gramicidin (5 microM). Consistent with these findings, a K(+)-selective membrane conductance was activated by exposing RBCs to a 0.5x Ringer solution (observed with the whole cell patch clamp technique). This conductance was inhibited by quinine (1 mM), gadolinium (10 microM), and pimozide (10 microM). These results indicate that cell swelling activates a K+ conductance by a Ca(2+)-calmodulin-dependent mechanism and that this channel mediates K+ loss during RVD.
研究了泥螈（Necturus maculosus）红细胞（RBC）调节性容积减小（RVD）的细胞基础。用K⁺替代细胞外Na⁺可抑制容积调节。相反，向细胞外培养基中添加短杆菌肽（5 μM）可增强RVD。K⁺通道阻滞剂奎宁（1 mM）也可抑制RVD，而短杆菌肽（5 μM）可逆转这种抑制作用。此外，0 Ca²⁺-EGTA林格液可阻断RVD，而Ca²⁺离子载体A23187（μM）可增强细胞容积的恢复。牵张激活离子通道拮抗剂钆（10 μM）可抑制RVD，而A23187（2 μM）可逆转这种作用。此外，钙调蛋白抑制剂匹莫齐特（10 μM）和N-（6-氨基己基）-5-氯-1-萘磺酰胺（0.1 mM）可阻断RVD，而短杆菌肽（5 μM）可逆转这种抑制作用。与这些发现一致，将RBC暴露于0.5倍林格液中可激活K⁺选择性膜电导（采用全细胞膜片钳技术观察到）。这种电导可被奎宁（1 mM）、钆（10 μM）和匹莫齐特（10 μM）抑制。这些结果表明，细胞肿胀通过Ca²⁺-钙调蛋白依赖性机制激活K⁺电导，且该通道在RVD过程中介导K⁺丢失。
