STUDIES ON THE ISOLATION AND PROPERTIES OF RENIN GRANULES FROM THE RAT-KIDNEY CORTEX

The present study was undertaken to isolate and investigate some physicochemical properties of renin granules from the rat kidney cortex. Two preparations of subcellular organelles were used: a primary-granule fraction, which allowed the properties of lysosomes to be compared simultaneously with those of renin granules, and a semi-purified preparation of the latter. The specific activity of renin in the primary-granule preparations was about 4-fold higher than in the original homogenate; that of the semi-purified renin-granule preparation was about 18-fold higher than in the homogenate, and consisted mainly of electron-dense granules but some mitochondria were also observed. Renin and acid phosphatase release from the primary-granule preparation was increased by lowering osmolality, by a low-molecular-weight solute (glucose) and by Triton X-100 or digitonin. Enzyme release was decreased by lowering the incubation temperature (4°C) or the presence of CaCl2. Renin release from the partially purified granule preparation was not affected by cyclic AMP, cyclic GMP and ATP.