title: Different isotonic density gradients in separation of renin granules from rat kidney cortex.
abstract: Crude renin granule preparations isolated from the rat renal cortex were further purified in isotonic conditions (300 mOsm/kg) using various density gradient materials. It was not possible to separate renin granules from other subcellular organelles using dextran, 40,000-sucrose or metrizamide-sucrose gradients at about 300 mOsm/kg. When osmolality of dextran-sucrose gradients was increased, some separation was found but both renin granules and mitochondria gained density. During a short centrifugation (4640 X g, 30 min) renin granules remained intact and appeared in two populations in Percoll-sucrose gradients. The apparently heavier (larger) particles (at 1.12-1.13 kg/l) were greatly purified from mitochondria (80 X purification vs. the whole homogenate), protein (120 X) and lysosomes (24 X). Electron micrographs demonstrated many dense core granules. The fraction containing apparently lighter (small) granules (at 1.08-1.09 kg/l) was heavily contaminated with mitochondria and lysosomes. During longer centrifugation (4640 X g, 60 min), only one major peak showing renin activity was observed at 1.12-1.13 kg/l, and other cell organelles were lighter. Hence the two renin populations evidently do not differ in density but rather in size. In the animals kept on a low-sodium diet, both types of renin granules were increased.
mesh_terms: D000818:Animals; D002458:Cell Fractionation / Q000379:methods*; D002499:Centrifugation, Density Gradient / Q000379:methods*; D003594:Cytoplasmic Granules / Q000648:ultrastructure*; D003911:Dextrans; D004039:Diet, Sodium-Restricted; D007552:Isotonic Solutions; D007672:Kidney Cortex / Q000648:ultrastructure*; D008297:Male; D008793:Metrizamide; D008854:Microscopy, Electron; D011205:Povidone; D051381:Rats; D012083:Renin / Q000378:metabolism*; D012822:Silicon Dioxide
chemical_list: D003911:Dextrans; D007552:Isotonic Solutions; C016039:Percoll; D012822:Silicon Dioxide; D012083:Renin; D011205:Povidone; D008793:Metrizamide