Low urine osmolarity as a determinant of cisplatin-induced nephrotoxicity.

Cisplatin is widely used in the treatment of human tumors, but it is a nephrotoxic drug. Early pragmatic clinical trials have shown that cisplatin-induced renal toxicity is greatly reduced through the use of high hydration, a large NaCl supply and mannitol infusion, but the precise mechanisms of these nephroprotective measures are not fully understood. We show here an increase in the cisplatin uptake and cytotoxicity on 56/10 A1 human glomerular and HK-2 human tubular cells when the drug incubation was performed in a hypotonic phosphate-buffered saline solution or in human urine ("drag in" transport hypothesis). When 4 mg/kg cisplatin was intraperitoneally injected in rats in 20 ml of a hypotonic 4 g/l NaCl solution, the platinum accumulation increased in both the cortex and papilla but not in the subcutaneously grafted colon tumors when compared to rats injected with cisplatin in normal or hyperosmotic solutions (9 and 14 g/l NaCl, respectively). The urea and creatinine blood levels were significantly increased, and more apoptotic cells were detected by the caspase-3 cleavage and TUNEL assays in the tubular cells of rats treated with cisplatin in a hypotonic solution compared to animals that received normal or hypertonic solutions. Osmolarity was sometimes low in urine from patients receiving an intravenous hydration for a cisplatin treatment or from healthy volunteers who were given an oral hydration with a 50 g/l glucose solution. Our results show that low urine osmolarity could be a major determinant in the increase of cisplatin-induced nephrotoxicity and justify the widely used concurrent infusion of osmotically active substances during intravenous hydration.

Intrarenal detection of nitric oxide using electron spin resonance spectroscopy in hypertensive lipopolysaccharide-treated rats.

The inhibition of nitric oxide (NO) synthesis by chronic administration of NG-nitro-l-arginine methyl ester (l-NAME) in rats is responsible for systemic hypertension. However, the mechanisms involved in this hypertension remain unclear. The effects of chronic l-NAME on kidney and blood NO production were studied in rats in a state of endotoxic shock due to lipopolysaccharide (LPS). A nitric oxide spin trapping technique using electron spin resonance (ESR) spectroscopy has been used to identify and measure the production of NO in the kidney. This method is based on the trapping of nitric oxide by a metal-chelator complex consisting of N-methyl-d-glucamine dithiocarbamate (MGD) and reduced iron (Fe2+) forming a water-soluble NO-FeMGD complex detected by ESR. After LPS injection (14 mg/kg, IV, 6 h before the sacrifice) to rats pretreated with l-NAME (10 mg/kg/d over 14 days), the NO-FeMGD complex was evaluated in the kidney (arbitrary units [AU]/g of kidney) and the density of polynuclear neutrophils was counted by light microscopy. Chronic inhibition of NO synthase by l-NAME, a nonspecific inhibitor, was responsible for a decrease of the NO-FeMGD complex levels in the kidney (24.9 +/- 1.6 AU versus 13.8 +/- 1.3 AU). LPS administration was responsible for a large increase in both NO-FeMGD complex and neutrophil levels in the kidney of normotensive rats (332.6 +/- 12.8 AU versus 24.9 +/- 1.6 AU for NO-FeMGD complex and 1.36 +/- 0.41 versus 0.11 +/- 0.03 for neutrophils). Conversely, LPS administration in hypertensive, l-NAME-pretreated rats was linked to a smaller increase in the NO-FeMGD complex (85.1 +/- 7.9 AU versus 332.6 +/- 12.8 AU) and a larger increase in glomerular neutrophils (2.48 +/- 0.36 versus 1.36 +/- 0.41) compared with normotensive rats. These results are in agreement with a direct implication of NO during LPS-and l-NAME-induced kidney injuries.