Lin J D
Department of Biology, National Cheng Kung University, Tainan, Taiwan, R.O.C.
Life Sci. 1988;43(4):325-33. doi: 10.1016/0024-3205(88)90110-5.
Potassium transport in microvessels isolated from rat brain by a technique involving density gradient centrifugation was studied in HEPES buffer solutions of varying osmolarity from 200 to 420 mosmols, containing different concentration of sodium chloride, choline chloride, or sodium nitrate. The flux of 86Rb (as a tracer for K) into and out of the endothelial cells was estimated. Potassium influx was very sensitive to the osmolarity of the medium. Ouabain-insensitive K-component was reduced in hypotonic medium and was increased in medium made hypertonic with sodium chloride or mannitol. Choline chloride replacement caused a large reduction in K influx. Potassium influx was significant decrease when nitrate is substituted for chloride ion in isotonic and hypertonic media, whereas a slight decrease was found in hypotonic medium. The decrease of K influx in the ion-replacement medium is due to a decrement of the ouabain-insensitive component. Potassium efflux was unchanged in hypotonic medium but was somewhat reduced in hypertonic medium. The marked effect of medium osmolarity on K fluxes suggests that these fluxes may be responsible for the volume regulatory K movements. The possible mechanism of changes of K flux under anisotonic media is also discussed.
通过密度梯度离心技术从大鼠脑部分离出微血管，在渗透压从200至420毫渗量、含有不同浓度氯化钠、氯化胆碱或硝酸钠的HEPES缓冲溶液中，研究钾离子转运。估算了86Rb（作为钾的示踪剂）进出内皮细胞的通量。钾离子内流对培养基的渗透压非常敏感。哇巴因不敏感的钾成分在低渗培养基中减少，在以氯化钠或甘露醇制成的高渗培养基中增加。用氯化胆碱替代会导致钾离子内流大幅减少。在等渗和高渗培养基中用硝酸根替代氯离子时，钾离子内流显著降低，而在低渗培养基中则略有降低。离子替代培养基中钾离子内流的减少是由于哇巴因不敏感成分的减少。钾离子外流在低渗培养基中不变，但在高渗培养基中有所减少。培养基渗透压对钾通量的显著影响表明，这些通量可能与钾的体积调节运动有关。还讨论了在非等渗培养基下钾通量变化的可能机制。
