Subcellular Localization of Renin in the Mouse Kidney

Abstract

A centrifugation study was carried out to investigate the subcellular localization of renin in the mouse kidney cortex. Renin activity was radioimmunoassayed and found mainly in the heavy mitochondrial fraction, with very little in the microsomal fraction, by differential centrifugation. Upon discontinuous sucrose density gradient centrifugation, renin granules were recovered mainly in the fraction corresponding to 1.5 м sucrose, while most of the mitochondria, lysosomes and microsomes equilibrated in the upper fractions. This renin granular fraction contained 53% of the total granular renin activity and had a specific activity 3.2 times that found in the unfractionated homogenate. After recentrifugation of the renin granular fraction, most of the renin activity was recovered in the sediment. Repeated freezing and thawing of this fraction resulted in an increase of renin activity, showing structure-linked latency. On the basis of these findings, it is assumed that renin in the mouse kidney cortex is located in granules which have a higher density than other subcellular particulates such as mitochondria, lysosomes and microsomes.