Different isotonic density gradients in separation of renin granules from rat kidney cortex.
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.
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
D003911:Dextrans; D007552:Isotonic Solutions; C016039:Percoll; D012822:Silicon Dioxide; D012083:Renin; D011205:Povidone; D008793:Metrizamide