Chemical Research in Toxicology 1989-01-01

Enzymatic defluorination and metabolism of fluoroacetate, fluoroacetamide, fluoroethanol, and (-)-erythro-fluorocitrate in rats and mice examined by 19F and 13C NMR.

B Tecle, J E Casida

Index: Chem. Res. Toxicol. 2(6) , 429-35, (1989)

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Abstract

Fluoroacetate administered intraperitoneally (ip) to rats and mice is defluorinated to give fluoride ion evident in urine and kidney by 19F NMR. The use of [2-13C]-, [1,2-13C]-, and [1,2-14C]fluoroacetate, prepared from isotopically labeled glycine, combined with 13C NMR and TLC radioautography, respectively, reveals a complex mixture of urinary metabolites including an S-(carboxymethyl) conjugate complex in rats and mice and sulfoxidation products thereof in rats. Direct 13C NMR examination of the bile following treatment with [2-13C]fluoroacetate shows the presence of S-(carboxymethyl)glutathione or a related conjugate and an O-conjugate of fluoroacetate. Incubation of [13C]fluoroacetate with rat and mouse liver cytosol involves formation of S-[( 13C]carboxymethyl)glutathione and fluoride ion. Fluorocitrate is also detected by 19F NMR examination of fluoroacetate incubations with mouse liver cytosol. Fluoroacetamide administered ip to rats and mice yields urinary fluoride ion formed via fluoroacetate which is liberated on hydrolysis by an organophosphate-sensitive amidase. 19F NMR chemical shifts of other metabolites of fluoroacetamide are consistent with fluoroacetohydroxamic acid in the liver of mice and fluorocitrate in the urine of rats. Fluoroethanol gives urinary fluoroacetate and fluoride ion in rats and mice and is converted to fluoroacetaldehyde by mouse and rat liver microsomes. (-)- and (+)-erythro-fluorocitrates administered ip to rats yield mostly the parent compounds in urine at 6 h with increasing amounts of fluoride ion thereafter. 19F NMR establishes that rat and mouse liver cytosols defluorinate (-)- but not (+)-erythro-fluorocitrate and pig heart aconitase also defluorinates (-)-erythro-fluorocitrate.(ABSTRACT TRUNCATED AT 250 WORDS)