Onuchic L F, Arenstein I R, Lopes A G
Department of Physiology, Faculdade de Medicina, Universidade de São Paulo, Brazil.
Am J Physiol. 1992 Sep;263(3 Pt 2):F353-62. doi: 10.1152/ajprenal.1992.263.3.F353.
Thin ascending limb cells of Henle's loop from Wistar rats were studied with in vitro microperfusion and video-optical techniques to investigate their ability in regulating cell volume during osmotic shock and to identify mechanisms of ion transport involved in the process. These cells showed a clear volume regulatory decrease (VRD) response in hyposmotic medium, but no volume regulatory increase in hyperosmotic medium. The presence of barium in the bath abolished VRD. Removal of K+ from bath and perfusate also inhibited the VRD response. Reintroduction of K+ in hyposmotic conditions reestablished cell volume regulation. Introduction of anthracene-9-COOH to the basolateral medium blocked cell volume regulatory response. Cl- removal from perfusate and bath solutions also inhibited VRD, probably because of a significant intracellular Cl- depletion. Exposure of cells to ethylene glycol-bis(beta-aminoethyl ether)-N,N,N'N'-tetraacetic acid in perfusate and bath solutions reduced significantly Ca2+ concentration and impaired VRD. Reintroduction of Ca2+ in hyposmotic conditions restored volume regulation. The presence of ouabain in basolateral medium also inhibited VRD. These data suggest that the following mechanisms in the basolateral membrane are involved in VRD response: K+ and Cl- conductive pathways, which might be Ca2+ dependent for activation, and an Na(+)-K(+)-adenosinetriphosphatase.
利用体外微灌注和视频光学技术对Wistar大鼠髓袢细段升支细胞进行了研究，以探讨其在渗透休克期间调节细胞体积的能力，并确定该过程中涉及的离子转运机制。这些细胞在低渗培养基中表现出明显的体积调节性减小（VRD）反应，但在高渗培养基中没有体积调节性增加。浴液中加入钡可消除VRD。从浴液和灌注液中去除K+也会抑制VRD反应。在低渗条件下重新加入K+可恢复细胞体积调节。向基底外侧培养基中加入蒽-9-羧酸可阻断细胞体积调节反应。从灌注液和浴液中去除Cl-也会抑制VRD，这可能是由于细胞内Cl-显著减少。将细胞暴露于灌注液和浴液中的乙二醇双（β-氨基乙醚）-N,N,N',N'-四乙酸中会显著降低Ca2+浓度并损害VRD。在低渗条件下重新加入Ca2+可恢复体积调节。基底外侧培养基中存在哇巴因也会抑制VRD。这些数据表明，基底外侧膜中的以下机制参与了VRD反应：K+和Cl-传导途径，其激活可能依赖于Ca2+，以及Na(+)-K(+)-三磷酸腺苷酶。
