Properties of renin granules isolated from rat kidney.

Renin granules from rat kidney prepared at 25 degrees C show greater stability at 25 degrees C than at 0 degrees C when incubated in ionic medium. The sum of the renin in the supernatant fluid plus that in the pellet was the same at 25 degrees C as at 0 degrees C, thus ruling out the possibility that the extra release at 0 degrees C merely represented greater stability of free renin at 0 degrees C. In common with other secretory granules, renin granules were most stable at pH 6.0 and were osmotically sensitive. In contrast to neurosecretory and chromaffin granules, renin granules were stabilized by Mg-ATP in ionic medium. This result is similar to studies by others on lysosomes. It is concluded that the renin granules membrane shares many of the properties of other granule membranes. Some of these properties (temperature and pH lability) will have to be considered in the design of future experiments on renin storage and release.