Ward P E, Erdös E G, Gedney C D, Dowben R M, Reynolds R C
Biochem J. 1976 Sep 1;157(3):643-50. doi: 10.1042/bj1570643.
Cortex of rat kidney was homogenized and fractions enriched in plasma membrane, endoplasmic reticulum or brush border were prepared by several techniques of differential centrifugation. The identity and homogeneity of the membrane fragments were investigated by assaying marker enzymes and by transmission and scanning electron microscopy. Kallikrein was present in both plasma-membrane- and endoplasmic-reticulum-enriched fractions isolated by two fractionation procedures. Kallikrein was highly concentrated in a plasma-membrane fraction but was absent from the brush-border membrane of proximal tubular cells. Cells of transplanted renal tumours of the rat, originating from the proximal tubule, had no kallikrein activity. Kininase activity, angiotensin I-converting enzyme (kininase II) and angiotensinase were found in a plasma-membrane-enriched fraction and especially in the fraction containing isolated brush border. It is suggested that after renal kallikrein is synthesized on endoplasmic reticulum, it is subsequently reoriented to a surface membrane for activation and release. Renal kallikrein may enter the tubular filtrate distal to the proximal tubules. The brush-border membrane of proximal tubule is the major site of inactivation of kinins and angiotensin II..
将大鼠肾皮质匀浆，通过几种差速离心技术制备富含质膜、内质网或刷状缘的组分。通过测定标记酶以及透射和扫描电子显微镜来研究膜片段的特性和均一性。通过两种分级分离程序分离得到的富含质膜和内质网的组分中均存在激肽释放酶。激肽释放酶高度浓缩在质膜组分中，但近端小管细胞的刷状缘膜中不存在。源自近端小管的大鼠移植肾肿瘤细胞没有激肽释放酶活性。在富含质膜的组分中，尤其是在含有分离刷状缘的组分中发现了激肽酶活性、血管紧张素I转换酶（激肽酶II）和血管紧张素酶。有人提出，肾激肽释放酶在内质网上合成后，随后重新定位到表面膜进行激活和释放。肾激肽释放酶可能进入近端小管远端的肾小管滤液中。近端小管的刷状缘膜是激肽和血管紧张素II失活的主要部位。
