Alterations of renal tissue structure during a 30-day gavage study with nitrilotriacetate.

Nitrilotriacetate (NTA), as the monohydrated trisodium salt, was administered by gavage to male Sprague-Dawley rats at levels of 0, 0.73 or 7.3 mmol/kg body weight/day for periods of up to 30 days. Two animals from each of the groups were killed 24 hr after dosing on day 9, 13, 16, 20, 23, 27 or 30. Cytoplasmic vacuolation and hyperplasia of the proximal convoluted tubules were the most prominent alterations observed by light microscopic examination of kidney tissue from both groups of NTA-treated rats. The number and severity of the lesions was greater in the high-dose group and in this group, erosion and hyperplasia of the pelvic transitional epithelium were also noted. The results of this study suggest that NTA-associated urinary tract lesions develop in a sequential pattern and that the rate and extent of these lesions is dose dependent.