Yamada K, Schulz W W, Page D S, Erdös E G
Hypertension. 1981 Nov-Dec;3(6 Pt 2):II-59-64. doi: 10.1161/01.hyp.3.6_pt_2.ii-59.
Basolateral membrane (BLM) enriched fraction was isolated from homogenized rat kidney cortex by differential centrifugation. We also obtained a fraction enriched in plasma membrane (PM). The morphology of the isolated BLM fragments was studied by transmission and freeze fracture electron microscopy. The relative specific activity of Na+-K+-ATPase was enriched 7-fold, while that of marker enzymes for PM, endoplasmic reticulum, and lysosomes was lower than in the crude homogenate. There was a 10-fold difference in the ratios of activities of Na+-k+-ATPase to Mg2+-ATPase in the BLM and in the PM enriched fractions. Kallikrein activity was determined with S-2266 substrate and by radioimmunoassay of kinin released. It was low in the BLM fraction prior to adding detergent, but Triton X-100 increased the activity 12 to 16-fold. Both free trypsin and Sepharose 4B-bound insoluble trypsin increased kallikrein activity 2- to 3-fold in both the membrane-bound and soluble fractions, probably by activating a prekallikrein. The results were interpreted that the kallikrein studied originated from the distal tubular BLM.
通过差速离心从匀浆的大鼠肾皮质中分离出富含基底外侧膜（BLM）的部分。我们还获得了富含质膜（PM）的部分。通过透射电子显微镜和冷冻断裂电子显微镜研究了分离出的BLM片段的形态。Na+-K+-ATP酶的相对比活性提高了7倍，而质膜、内质网和溶酶体的标记酶的比活性低于粗匀浆。在富含BLM和PM的部分中，Na+-K+-ATP酶与Mg2+-ATP酶的活性比值相差10倍。用S-2266底物并通过放射免疫分析法测定释放的激肽来确定激肽释放酶活性。在添加去污剂之前，BLM部分的活性较低，但Triton X-100可使活性提高12至16倍。游离胰蛋白酶和结合在Sepharose 4B上的不溶性胰蛋白酶均可使膜结合部分和可溶性部分中的激肽释放酶活性提高2至3倍，可能是通过激活前激肽释放酶来实现的。结果表明，所研究的激肽释放酶起源于远端肾小管的BLM。
