Sodium and water excretion in nephrotic patients: effects of changes in renal haemodynamics

Role of sodium during formation of edema in children with nephrotic syndrome

BACKGROUND

The pathogenesis of edema in nephrotic syndrome is not entirely understood. The aim of this study was to contribute to the discussion on edema pathogenesis in nephrotic syndrome by following changes in volume and sodium retention for the course of the disease in children with steroid-sensitive nephrotic syndrome (SSNS).

METHODS

Forty-one children with SSNS were included in the study. The patients were divided into three groups (group I: relapse-edematous; group II: relapse-edema free; group III: remission). We investigated the value of the significance and area of sodium retention and vasoactive hormones. In addition, we measured parameters such as inferior vena cava collapsibility index, left atrium diameter, and total body water (TBW) to determine the volume load and cause of edema in children with SSNS.

RESULTS

TBW increased in the relapse-nephrotic syndrome group and the difference was statistically significant among groups (P < 0.001). However, inferior vena cava collapsibility index and left atrium diameter were not different among groups. Fractional sodium excretion was lower in children with relapse nephrotic syndrome (P < 0.05).

CONCLUSION

Although TBW increases in children with SSNS, intravascular volume is normal. In addition, hypoalbuminemia and sodium retention of the proximal tubule cause edema in children with SSNS.

Molecular pathogenetic mechanisms of nephrotic edema: progress in understanding

Molecular and pathogenetic mechanisms in sodium retention and water reabsorption of nephrotic edema are discussed. Are reported and analyzed molecular mechanisms about sodium retention in collecting duct cells regarding activation and surface expression of epithelial sodium channels (ENaC) and sodium-potassium-ATPase (Na,K-ATPase) by aldosterone, vasopressin, natriuretic peptide system (underfill theory): is necessary a better understanding about the dysregulation of ENaC and Na,K-ATPase surface expression and the resistance to natriuretic peptide system. Are also reported and analyzed molecular mechanisms of sodium retention in proximal tubule cells regarding intrinsic albumin toxicity upon type 3 sodium-hydrogen exchanger ionic pump and the activity of sodium-hydrogen exchanger regulatory factor protein (overfill theory): a better knowledge about the link between albumin, sodium-hydrogen exchanger type 3 (NHE3) ionic pump, sodium-hydrogen exchanger regulatory factor protein is necessary. Then molecular mechanisms of vasopressin free water retention through acquaporin water channels in collecting duct cells are discussed: further studies are necessary to understand vasopressin release pathway (osmotic/nonosmotic) and V2 receptor activation with cell surface expression of renal acquaporins water channel.

Regulation of the proximal tubular sodium/proton exchanger NHE3 in rats with puromycin aminonucleoside (PAN)-induced nephrotic syndrome

Excessive proteinuria due to loss of glomerular permselectivity in nephrotic syndrome can cause disturbances in renal salt and water handling with edema formation. Apart from oncotic and hydrostatic mechanisms associated with hypoalbuminemia, primary derangements in renal tubular sodium transport may contribute to the pathogenesis of nephrotic edema. Whereas there is evidence for an increase of cortical collecting duct sodium reabsorption in nephrotic rats, it remains controversial whether proximal tubule sodium transport may also be activated in this condition. The regulation of the cortical Na/H exchanger NHE3, the main pathway for Na reabsorption in the proximal tubule (PT), was investigated in rats with puromycin aminonucleoside (PAN)-induced nephrotic syndrome. PAN rats developed reduced GFR, severe proteinuria, and sodium retention within 3 d. After 10 d, immunoblots of brush border vesicles revealed a decreased abundance of NHE3 in nephrotic animals. However, the Na/H antiporter activity in the same vesicle preparations was not significantly altered. Antiporter activity normalized for NHE3 protein was increased by 88% in nephrotic animals (P = 0.025). Immunohistochemistry with the same polyclonal antibody as for immunoblots revealed a decrease of NHE3 abundance in PT. In contrast, immunoreactivity for the monoclonal antibody 2B9, which specifically recognizes the non-megalin-associated, transport-competent pool of NHE3, was higher in PAN-treated rats than in controls. In conclusion, increased sodium reabsorption might be associated with a shift of NHE3 from an inactive pool to an active pool, thus contributing to sodium retention in a state of proteinuria.

Determinants of impaired renal function with use of nonsteroidal anti-inflammatory drugs: the importance of half-life and other medications

PURPOSE

Nonsteroidal anti-inflammatory drugs (NSAIDs) may interfere with renal function, but little is known about the effects of the half-life of these agents, or the use of other medications, on renal function.

SUBJECTS AND METHODS

Medication use was assessed during a standardized interview in a cross-sectional study of 802 patients undergoing total joint replacement because of osteoarthritis. Preoperative blood samples were used to estimate creatinine clearance using a standard formula that takes age, sex, and weight into account. Impaired renal function was defined as an estimated creatinine clearance less than 60 mL/min (fifteenth percentile). Multivariable logistic regression was used to estimate the adjusted odds ratios (OR) and 95% confidence intervals (CI) for the association between NSAID use (alone or in combination with diuretics or angiotensin-converting enzyme [ACE] inhibitors) and impaired renal function.

RESULTS

NSAID use per se was only marginally associated with impaired renal function (OR = 1.4; 95% CI, 0.9 to 2.2). This association was almost exclusively the result of the use of NSAIDs with a half-life of 4 or more hours (OR = 2.6; 95% CI: 1.2 to 5.7). Patients who used diuretics with NSAIDs (OR = 3.7; 95% CI: 1.7 to 8.3) or without NSAIDs (OR = 3.5; 95% CI: 1.6 to 7.6) had a higher risk of impaired renal function than did patients using NSAIDs alone (OR = 1.6) or none of these drugs (reference). A similar but less pronounced pattern was observed for ACE inhibitors.

CONCLUSION

NSAID-associated impaired renal function seems to be mainly the result of compounds with intermediate-long half-life. We found no evidence that the adverse effects of diuretics and ACE inhibitors on renal function were greater in those who also used NSAIDs.