Specific Distribution of Renin Binding Protein in Rat and Dog Kidney

Localization of renin binding protein in the renal cortex of the rat and dog was investigated. Glomeruli and tubules were separated from the renal cortex by microdissection and proteins were extracted by repeated freezing and thawing. The low-molecular weight renin (Mr:40,000) was obtained from the isolated renin granules. The molecular weight of renin was estimated by high performance liquid chromatography. The extract of isolated glomeruli contained the low-molecular-weight renin, and the molecular size of renin remained unchanged by addition of sodium tetrathionate. On the other hand, high-molecular-weight renin (Mr:60,000) was formed when the extract of isolated tubular segments was mixed with the low-molecular-weight renin, in the presence of sodium tetrathionate. These results indicate that the renin binding protein is located in the tubules of the cortex, but not in the glomeruli of the kidney.