Distinct Localization of Renin and Angiotensins in Separate Subcellular Fractions of the Rat Adrenal Cortex

Abstract

The subcellular localization of renin and immunoreactive angiotensins I and II was studied in rat adrenal cortical tissues. The identity of the immunoreactive angiotensins was confirmed as angiotensin I and angiotensin II by radioimmunoassay and high-performance liquid chromatography, respectively, with reference to standard compounds. By differential centrifugation of tissue homogenate in 0.25 M sucrose/30 mM Tris-HCl/1 mM EDTA, pH 7.4, specific immunoreactive renin was found to be localized principally (60%) in the mitochondrial fraction (P₂), whereas about 40% of both angiotensins I and II was contained in the soluble fraction; only 18-20% of both peptides was contained in the P₂ fraction. On Percoll density gradient centrifugation of P₂, renin was fractionated mostly in a denser band whereas angiotensins I and II were contained in a lighter density area closely corresponding to mitochondrial and lysosomal marker enzymes. These results suggest that renin and angiotensins in the cells of the rat adrenal gland reside in different subcellular compartments and argue against intracellular formation of angiotensins by renin in renin granules.