Lin J D
Jpn J Physiol. 1985;35(5):817-30. doi: 10.2170/jjphysiol.35.817.
Microvessels have been prepared from the gray matter of a rat brain by a technique involving density gradient centrifugation. A suspension of these vessels, largely capillaries, was incubated in vitro in order to investigate K transport. The flux of K (as 86Rb) into and out of endothelial cells was estimated. Potassium influx was sensitive to temperature and pH of the medium, and was markedly inhibited by 1 mM ouabain (45%). Ouabain did not inhibit K efflux, as anticipated, when Na-K pumps are mainly located on the abluminal plasma membrane of the endothelial cell. The ouabain-sensitive K influx was measured at varying external concentrations of K. The Km of ouabain-sensitive K influx was 2.95 mM, which is similar to the affinity of the transport carrier of K, found in in vivo studies of K efflux from brain to the blood system. Both 1 mM furosemide and 5 mM barium chloride inhibited part of the ouabain-insensitive K influx. Potassium efflux was not influenced by furosemide, but was somewhat reduced by barium chloride. Noradrenalin (10(-3) mM) and histamine (0.1 mM) did not significantly affect the influx of K.
通过密度梯度离心技术从大鼠脑灰质中制备微血管。为了研究钾离子转运，将这些主要为毛细血管的血管悬浮液进行体外培养。估算了钾离子（以86Rb形式）进出内皮细胞的通量。钾离子内流对培养基的温度和pH敏感，并被1 mM哇巴因显著抑制（45%）。正如预期的那样，由于钠钾泵主要位于内皮细胞的基底外侧质膜上，哇巴因并未抑制钾离子外流。在不同的细胞外钾离子浓度下测量了对哇巴因敏感的钾离子内流。对哇巴因敏感的钾离子内流的米氏常数为2.95 mM，这与在脑向血液系统钾离子外流的体内研究中发现的钾离子转运载体的亲和力相似。1 mM呋塞米和5 mM氯化钡均抑制了部分对哇巴因不敏感的钾离子内流。钾离子外流不受呋塞米影响，但被氯化钡略微降低。去甲肾上腺素（10(-3) mM）和组胺（0.1 mM）对钾离子内流无显著影响。
