Usefulness of the assessment of urinary enzyme leakage in monitoring acutefluoride nephrotoxicity

A single oral dose of sodium fluoride (NaF) in aqueous solution was given t o male Wister rats. Twenty-four-hour urine samples were collected and exami ned to evaluate fluoride-induced acute renal damage. The following paramete rs were measured in 24-h urine: urine volume and urinary excretion of fluor ide, N-acetyl-beta-D-glucosaminidase (NAG), alpha-glutathione-S-transferase (alpha-GST), and creatinine (CR). Fluoride exposure produced specific. dos e-dependent changes of these parameters. Significant increases of fluoride and fluoride-induced polyuria were observed. NAG as specific marker of prox imal convoluted tubule (PCT) function showed a significant increase when th e lowest dose of fluoride was administered. At this minimal dose, alpha-GST , a specific marker for the S3 segment, did not show a significant increase but presented the strongest relationship (r = 0.83) to fluoride dose. No s ignificant changes were measured for CR excretion, which showed a low corre lation coefficient (r = 0.36) to administered fluoride. The specific differ ences in the increase pattern of these parameters show that the PCT is more susceptible to damage by low-dose fluoride than the S3 segment or the glom erulus. We concluded that both NAG and alpha-GST are useful for the diagnos is of fluoride-induced acute nephrotoxicity. Proper evaluation of these uri nary indices may be of help to establish the site and extent of kidney inju ry in acute fluoride toxicity.