Tissue kallikrein and kinins in renal disease

The renal kallikrein-kinin system is involved in sodium and water homeostasis, blood pressure regulation and inflammation. Tissue kallikrein and kinin levels were measured in the urine of patients with renal disease and in the urine of living related kidney donors prior to uninephrectomy who served as controls. Tissue kallikrein and kinin B1 and B2 receptors were immunolocalised by confocal microscopy in renal biopsy material from patients with renal disease and controls (fresh autopsy material and normal kidney tissue from nephrectomies for malignancy). Urinary tissue kallikrein excretion was significantly decreased in patients with mild renal disease (16.6 +/- 6.7 ng tissue kallikrein (TK)/ng protein; p < 0.05) and more markedly so (1.8 +/- 0.7 ng TK/microg protein; p < 0.01) in patients with severe renal failure requiring dialysis compared to normal controls (78.9 +/- 31.7 ng TK/microg protein). Basal kinin values were unchanged in patients with renal disease (14 +/- 0.8 ng/ml) compared to controls (13.3 +/- 0.56 ng/ml). In control kidney tissue kallikrein was immunolocalised in the distal connecting tubules and collecting ducts whereas decreased immunolabelling was observed with renal disease. Kinin B2 receptor labelling was present in the entire nephron in the normal control kidney but was reduced with renal disease. While kinin B1 receptor immunolabelling was not observed in the control kidneys, labelling of distal tubules and collecting ducts was noted in renal disease, suggesting an upregulation of B1 receptors in renal parenchymal disease.