Functional, biochemical, and molecular investigations of renal kallikrein-kinin system in diabetic rats

A reduction of renal kallikrein has been found in non-insulin-treated diabetic individuals, suggesting that an impaired renal kallikreinkinin system (KKS) contributes to the development of diabetic nephropathy. We analyzed relevant components of the renal KKS in non-insulin-treated streptozotocin (STZ)-induced diabetic rats. Twelve weeks after a single injection of STZ, rats were normotensive and displayed hyperglycemia, polyuria, proteinuria, and reduced glomerular filtration rate. Blood bradykinin (BK) levels and prekallikrein activity were significantly increased compared with controls. Renal kallikrein activity was reduced by 70%, whereas urinary BK levels were increased up to threefold. Renal kininases were decreased as indicated by a 3-fold reduction in renal angiotensin-converting enzyme activity and a 1.8-fold reduction in renal expression of neutral endopeptidase 24.11. Renal cortical expression of kininogen and Bg receptors was enhanced to 1.4 and 1.8-fold, respectively Our data suggest that increased urinary BK levels found in severely hyperglycemic STZ-diabetic rats are related to increased filtration of components of the plasma KKS and/or renal kininogen synthesis in combination with decreased renal kinin-degrading activity. Thus, despite reduced renal kallikrein synthesis, renal KKS is activated in the advanced stage of diabetic nephropathy.Free Univ Berlin, Klinikum Benjamin Franklin, Dept Cardiol & Pneumol, D-12200 Berlin, GermanyUniv Kiel, Inst Pharmacol, D-24105 Kiel, GermanyUniv Heidelberg, Dept Pharmacol, D-69115 Heidelberg, GermanyUniv Heidelberg, Dept Nephrol, D-69115 Heidelberg, GermanyMax Delbruck Ctr Mol Med, D-13092 Berlin, GermanyHumboldt Univ, Dept Med Cardiol, Virchow Klinikum, D-13353 Berlin, GermanyUniv Fed Sao Paulo, Dept Biophys, Sao Paulo, BrazilUniv Fed Sao Paulo, Dept Biophys, Sao Paulo, BrazilWeb of Scienc