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Granules of the submaxillary gland of the white mouse contain both kallikrein and renin. The granules were separated and concentrated in sequential centrifugation procedures. They were more stable at room temperature and in hypertonic sucrose solutions than in the cold or in isotonic solution. The amylase, acid phosphatase, renin, kallikrein, and benzoyl-L-arginine ethyl ester esterase contents of the granules were determined. Kallikrein and renin showed a similar distribution pattern after fractionation. Granular renin released the equivalent of 9. Electron micrographs of the isolated granules showed various forms; some were spherical and symmetrical, and others were amorphous. ADDITIONAL KEY WORDSsubmaxillary gland bradykinin angiotensin subcellular fractions electron microscopy differential centrifugation insoluble enzyme polymers kallidin• Granules originating from the rat submaxillary gland contain large amounts of kallikrein ( 1 ) . The appearance of these particles in electron micrographs is similar to that of pancreatic zymogen granules (2). Although the presence of renin in granules has been gaining acceptance, a definite relationship between granules and renin activity has not yet been established (3,4 ) . In addition to kallikrein, renin was found in the submaxillary glands of the white mouse (5-8). Renin activity is concentrated in the striated ducts which have granulated cells. These findings led us to study the subcellular distribution of renin and its relationship to kallikrein in the submaxillary gland of the white mouse. In the present communication we deal withFrom the Departments of Pharmacology and Pathology, University of Oklahoma, School of Medicine, Oklahoma City, Oklahoma 73104.This work was supported in part by U. S. Public Health Service Grant HE 08764 from the National Institutes of Health.When this work was done Dr. Miwa was a fellow of the Oklahoma Heart Association. His permanent address is Department of Medicine, Tohoku University, Sendai, Japan.Accepted for publication August 5, 1968.the isolation of an active, granular layer that contains both kallikrein and renin.Methods White male Swiss Webster mice (A. Sutter Co.) were killed by a sudden blow on the head without using anesthesia. The mice were over 90 days old and weighed about 50 g. Fresh, minced submaxillary glands were homogenized in batches of six pairs in a Dounce hand homogenizer. In the first series of experiments, the tissues were placed in a medium of 0.25M sucrose solution buffered with 0.005M Tris, pH 7.4, in an ice bath. A 10% (w/v) homogenate was prepared and filtered through four layers of gauze. The filtered homogenate was then fractionated using isotonic sucrose solutions and a refrigerated centrifuge as previously described (1).In the second series of experiments, all procedures were done at room temperature in a 0.88M sucrose solution buffered with 0.005M Tris, pH 7.4. The unbroken cells and tissues were removed by centrifugation at 120 g for 5 minutes using a Sorvall RC-2 centrifuge. The step was rep...

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