ABSTRACT
AIM: Recent work has demonstrated that activation of the epithelial sodium channel (ENaC) by aberrantly filtered serine proteases causes sodium retention in nephrotic syndrome. The aim of this study was to elucidate a potential role of plasma kallikrein (PKLK) as a candidate serine protease in this context. METHODS: We analysed PKLK in the urine of patients with chronic kidney disease (CKD, n = 171) and investigated its ability to activate human ENaC expressed in Xenopus laevis oocytes. Moreover, we studied sodium retention in PKLK-deficient mice (klkb1-/- ) with experimental nephrotic syndrome induced by doxorubicin injection. RESULTS: In patients with CKD, we found that PKLK is excreted in the urine up to a concentration of 2 µg mL-1 which was correlated with albuminuria (r = .71) and overhydration as assessed by bioimpedance spectroscopy (r = .44). PKLK increased ENaC-mediated whole-cell currents, which was associated with the appearance of a 67 kDa γ-ENaC cleavage product at the cell surface consistent with proteolytic activation. Mutating a putative prostasin cleavage site in γ-ENaC prevented channel stimulation by PKLK. In a mouse model for nephrotic syndrome, active PKLK was present in nephrotic urine of klkb1+/+ but not of klkb1-/- mice. However, klkb1-/- mice were not protected from ENaC activation and sodium retention compared to nephrotic klkb1+/+ mice. CONCLUSION: Plasma kallikrein is detected in the urine of proteinuric patients and mice and activates ENaC in vitro involving the putative prostasin cleavage site. However, PKLK is not essential for volume retention in nephrotic mice.
Subject(s)
Epithelial Sodium Channels/metabolism , Kidney/enzymology , Natriuresis , Nephrotic Syndrome/enzymology , Plasma Kallikrein/metabolism , Water-Electrolyte Balance , Adult , Aged , Animals , Body Composition , Case-Control Studies , Disease Models, Animal , Doxorubicin , Epithelial Sodium Channels/genetics , Female , Humans , Kidney/physiopathology , Male , Membrane Potentials , Mice, Knockout , Middle Aged , Nephrotic Syndrome/genetics , Nephrotic Syndrome/physiopathology , Nephrotic Syndrome/urine , Organism Hydration Status , Plasma Kallikrein/genetics , Plasma Kallikrein/urine , Prospective Studies , Renal Elimination , Renal Insufficiency, Chronic/enzymology , Renal Insufficiency, Chronic/physiopathology , Renal Insufficiency, Chronic/urine , Xenopus laevisABSTRACT
We determined the sensitivity of computed tomography and color duplex ultrasonography in the detection and characterization of vascular complications in acute pancreatitis. The relationship of these complications with the etiology and activity of the disease was assessed. In a prospective study, 189 patients with acute pancreatitis seen in the Department of Gastroenterology. Charité Hospital in Berlin over a period of 38 months underwent color duplex ultrasonography every second day for 3 weeks and thereafter at least once a week for 2 months. Dynamic computed tomography was performed within 72 hours after admission, and follow-up computed tomography scans were obtained. In 45 patients (23%), at least temporary thromboses of portal venous vessels were demonstrated by color duplex ultrasonography. The incidence of venous thromboses was 30% in severe acute pancreatitis with fluid collections without necroses and 57% in necrotizing pancreatitis. In 27 of those 45 patients, a formation of collaterals was documented. In 13 patients, arterial pseudoaneurysms were demonstrated. Vascular complications were significantly more frequent in alcohol-induced than in gallstone-induced pancreatitis. Only 62% of all sonographically diagnosed thromboses and only 32% of all collaterals were demonstrated by computed tomography. The prevalence of vascular complications in acute pancreatitis was much higher as suspected. The risk of gastrointestinal bleeding was lower than previously reported. Color duplex sonography is the method of choice for the detection of vascular complications in acute pancreatitis.