FORMIC-ACID EXCRETION IN RATS EXPOSED TO TRICHLOROETHYLENE - A POSSIBLE EXPLANATION FOR RENAL TOXICITY IN LONG-TERM STUDIES

Rats exposed to trichloroethylene, either by gavage or by inhalation, excreted large amounts of formic acid in urine which was accompanied b y a change in urinary pH, increased excretion of ammonia, and slight i ncreases in the excretion of calcium. Following a single 6-h exposure to 500 ppm trichloroethylene, the excretion of formic acid was compara ble to that seen after a 500 mg/kg dose of formic acid itself, yet the half-life was markedly different. Formate excretion in trichloroethyl ene treated rats reached a maximum on day 2 and had a half-life of 4-5 days, whereas urinary excretion was complete within 24 h following a single dose of formic acid itself. Formic acid was shown not to be a m etabolite of trichloroethylene. When rats were exposed to 250 or 500 p pm trichloroethylene, 6 h/day, for 28 days, the only significant effec ts were increased formic acid and ammonia excretion, and a change in u rinary pH. There was no evidence of morphological liver or kidney dama ge. Long-term exposure to formic acid is known to cause kidney damage suggesting that excretion of this acid may contribute to the kidney da mage seen in the long-term studies with trichloroethylene. (C) 1998 El sevier Science Ireland Ltd. All rights reserved.