Fluoride ion toxicity in rabbit kidney thick ascending limb cells

Some halogenated agents, especially methoxyflurane, because of a higher level of fluoride production, induce a renal concentrating defect that could be related to an ascending limb impairment. We investigated the mechanisms of fluoride toxicity on an immortalized cell line.

Cells were cultured for 2, 6 or 24 h in the presence of fluoride. Toxicity evaluation was based on: cell numbers, protein content, leucine-incorporation, lactate dehydrogenase (LDH) and N-acetyl-beta-glucosaminidase (NAG) releases, Na-K-ATPase and Na-K-2Cl activities, electron microscope studies. Infrared analysis and fluoride microdetermination allowed crystal components.

At 5 mmol after 24 h, fluoride decreased cell numbers (-14%, *P < 0.05), protein content (-16%*), leucine incorporation (-54%*), Na-K-2Cl activity (-84%*), increased LDH (+145%*) and NAG release (+190%*). Na-K-ATPase was more sensitive and impaired from 1 mmol for 24h and after 2 h at 5 mmol. Crystal formation in mitochondria occurred after 6 h at 5 mmol. Infra-red analysis and fluoride microdetermination established that crystals contained sodium, phosphate and fluoride.

The results suggest that the Na-K-ATPase pump is a major target for fluoride toxicity in Henle's loop.