Effects of Sodium Intake on Urinary Excretion and Renal Content of Bradykinin and its Metabolites in Rats

Abstract

The kallikrein-kinin system (KKS) is present in the kidney and numerous studies have characterized the intrarenal distribution of its components. Kallikreins are principally found in the cortex (1). In isolated nephron of rats and rabbits, kallikreins are found in the granular portion of the cortical distal and collecting tubules (2,3,4). The distribution of the substrate was studied by Proud et al. (5), using immunofluorescent method. It was found that kininogen, probably of low molecular weight, was present all along the proximal and distal tubules of the cortex and the medulla. Since enzymes and substrate for the formation of kinins are present in the nephron, studies have been conducted to identify the site of generation of kinins in the tubules. By stop-flow analysis, Scicli et al. (6) have demonstrated the presence of kinins in the distal nephron with high concentration in the final segment. Finally, the search for the presence of receptors for kinins have been conducted in isolated nephron of the rabbit and they are present in the collecting tubules of the cortex and the medulla (7). Thus, the pattern of distribution of the various components, found mainly in the distal portion of the nephron, an important site controlling the final excretion of water and electrolytes, suggests that kinins participate to the excretory functions of the kidneys.