Distribution of renin in subcellular fractions from the rabbit kidney

Subcellular localization of renin in the rabbit kidney cortex was investigated using two centrifugation techniques. Renin was indirectly assayed on the basis of pressor activity and the reference enzymes such as succinic dehydrogenase, acid phosphatase and D-glucose-6-phosphatase for the other subcellular particulates were biochemically determined. Renin activity was found mainly in the mitochondrial fraction with very little in the microsomal fraction by a differential centrifugation. By a discontinuous sucrose density gradient centrifugation, renin granules were mainly recovered in the fraction corresponding to 1.5 M sucrose, while most of mitochondria, lysosomes and microsome equilibrated in the upper fractions. This renin granular fraction contained approximately 50% of total granular renin activity having a specific activity about six times that seen in the homogenate. After recentrifugation of the renin granular fraction, most of renin activity was recovered in the sediment. Repeated freezing and thawing of this fraction resulted in an increase of renin activity. On the basis of these experimental data it is assumed that renin located in the different subcellular particulates from mitochondria, lysosomes and microsomes in the rabbit kidney cortex.