[Urinary excretion of phospholipids: index of aminoglycoside nephrotoxicity]

Aminoglycosides have a low molecular weight and bind weakly to proteins. They are easily filtered through the glomeruli, bind to phospholipid receptors located on the brush border of proximal tubule cells, and penetrate within the cells by endocytosis. Aminoglycosides decrease lysosomal A and C phospholipase and sphingomyelinase activities. This impairs the degradation of phospholipids, with formation of abnormal intralysosomal structures called myeloid bodies as a result. These myeloid bodies are gradually eliminated from the cells into the lumen of the tubule and excreted in the urine. We studied the urinary excretion of phospholipids following 1, 3, 5 and 10 days of treatment with gentamicin (3 mg/kg/day) or tobramycin (3 mg/kg/day) in patients with acute pyelonephritis. Infection-free, non-treated subjects were used as controls. Patients with a urinary tract infection treated by a quinolone made up a third group. Urinary N-acetyl-beta-D-glucosaminidase (NAG), an indicator of epithelial necrosis, was also evaluated. Results were expressed per ml urine, per mg creatinine and per 24 hours. Only the results expressed per mg creatinine appeared valid. No significant increase in serum creatinine or urinary NAG was found in patients under gentamicin. In the patients with a urinary tract infection not treated with an aminoglycoside, urinary phospholipid excretion on D1 was decreased as compared to controls (p less than 0.01). Urinary phospholipid excretion was never found to be increased in patients under aminoglycosides. No significant difference was found between males and females. Mistaken interpretations occurred if urinary excretion of phospholipids or NAG was not expressed per mg creatinine.(ABSTRACT TRUNCATED AT 250 WORDS)