The aim of the present study was to determine whether acute sodium overload could trigger an inflammatory reaction in the tubulointerstitial (TI) compartment in normal rats. Four groups of Sprague-Dawley rats received increasing NaCl concentrations by intravenous infusion. Control (C): Na+ 0.15 M; G1: Na+ 0.5 M; G2: Na+ 1.0 M; and G3: Na+ 1.5 M. Creatinine clearance, mean arterial pressure (MAP), renal blood flow (RBF), and sodium fractional excretion were determined. Transforming growth factor beta1 (TGF-beta1), alpha-smooth muscle actin (alpha-SMA), RANTES, transcription factor nuclear factor-kappa B (NF-kappaB), and angiotensin II (ANG II) were evaluated in kidneys by immunohistochemistry. Animals with NaCl overload showed normal glomerular function without MAP and RBF modifications and exhibited a concentration-dependent natriuretic response. Plasmatic sodium increased in G2 (P < 0.01) and G3 (P < 0.001). Light microscopy did not show renal morphological damage. Immunohistochemistry revealed an increased number of ANG II-positive tubular cells in G2 and G3, and positive immunostaining for NF-kappaB only in G3 (P < 0.01). Increased staining of alpha-SMA in the interstitium (P < 0.01), TGF-beta1 in tubular cells (P < 0.01), and a significant percentage (P < 0.01) of positive immunostaining for RANTES in tubular epithelium and in glomerular and peritubular endothelium were detected in G3 > G2 > C group. These results suggest that an acute sodium overload is able 'per se' to initiate TI endothelial inflammatory reaction (glomerular and peritubular) and incipient fibrosis in normal rats, independently of hemodynamic modifications. Furthermore, these findings are consistent with the possibility that activation of NF-kappaB and local ANG II may be involved in the pathway of this inflammatory process.

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The aim of this work was to study the role of local intrarenal angiotensin II (Ang II) and the oxidative stress in the up-regulation of pro-inflammatory cytokines expression observed in rats submitted to an acute sodium overload. Sprague-Dawley rats were infused for 2 h with isotonic saline solution (Control group) and with hypertonic saline solution alone (Na group), plus the AT1 receptor antagonist losartan (10 mg kg(-1) in bolus) (Na-Los group), or plus the superoxide dismutase mimetic tempol (0.5 mg min(-1) kg(-1)) (Na-Temp group). Mean arterial pressure, glomerular filtration rate, and fractional sodium excretion (FE(Na)) were measured. Ang II, NF-kappaB, hypoxia inducible factor-1 alpha (HIF-1 alpha), transforming growth factor beta1 (TGF-beta1), smooth muscle actin (alpha-SMA), endothelial nitric oxide synthase (eNOS), and RANTES renal expression was evaluated by immunohistochemistry. Ang II, NF-kappaB, and TGF-beta1 and RANTES early inflammatory markers were overexpressed in Na group, accompanied by enhanced HIF-1 alpha immunostaining, lower eNOS expression, and unmodified alpha-SMA. Losartan and tempol increased FE(Na) in sodium overload group. Although losartan reduced Ang II and NF-kappaB staining and increased eNOS expression, it did not restore HIF-1 alpha expression and did not prevent inflammation. Conversely, tempol increased eNOS and natriuresis, restored HIF-1 alpha expression, and prevented inflammation. Early inflammatory markers observed in rats with acute sodium overload is associated with the imbalance between HIF-1 alpha and eNOS expression. While both losartan and tempol increased natriuresis and eNOS expression, only tempol was effective in restoring HIF-1 alpha expression and down-regulating TGF-beta1 and RANTES expression. The protective role of tempol, but not of losartan, in the inflammatory response may be associated with its greater antioxidant effects.

The aim of this study was to demonstrate the effects of atrial natriuretic peptide (ANP) on organic cation transporters (OCTs) expression and activity, and its consequences on dopamine urinary levels, Na+, K+-ATPase activity and renal function. Male Sprague Dawley rats were infused with isotonic saline solution during 120 minutes and randomized in nine different groups: control, pargyline plus tolcapone (P+T), ANP, dopamine (DA), D-22, DA+D-22, ANP+D-22, ANP+DA and ANP+DA+D-22. Renal functional parameters were determined and urinary dopamine concentration was quantified by HPLC. Expression of OCTs and D1-receptor in membrane preparations from renal cortex tissues were determined by western blot and Na+, K+-ATPase activity was determined using in vitro enzyme assay. 3H-DA renal uptake was determined in vitro. Compared to P+T group, ANP and dopamine infusion increased diuresis, urinary sodium and dopamine excretion significantly. These effects were more pronounced in ANP+DA group and reversed by OCTs blockade by D-22, demonstrating that OCTs are implied in ANP stimulated-DA uptake and transport in renal tissues. The activity of Na+, K+-ATPase exhibited a similar fashion when it was measured in the same experimental groups. Although OCTs and D1-receptor protein expression were not modified by ANP, OCTs-dependent-dopamine tubular uptake was increased by ANP through activation of NPR-A receptor and protein kinase G as signaling pathway. This effect was reflected by an increase in urinary dopamine excretion, natriuresis, diuresis and decreased Na+, K+-ATPase activity. OCTs represent a novel target that links the activity of ANP and dopamine together in a common mechanism to enhance their natriuretic and diuretic effects.