Metabolism and excretion of [14C]furfural in the rat and mouse.

The fate of furfural (2-furancarboxaldehyde) was investigated in male and female Fischer 344 (F344) rats given single oral doses of 1, 10 and 60 mg/kg and male and female CD1 mice given 1, 20 and 200 mg/kg [carbonyl-14C]furfural. There was a very high recovery (more than 90% of dose) of radioactivity in all dose groups in 72 hr. The major route of elimination was by the urine, with much smaller amounts present in the faeces and exhaled as 14CO2. The residue in the carcass after 72 hr was less than 1% of the administered dose. Furoylglycine and furanacryloylglycine were identified as the major urinary metabolites by high-performance thin-layer chromatography, radio-HPLC, gas chromatography-mass spectrometry and 1H-nuclear magnetic resonance spectroscopy, by comparison with synthetic reference compounds. There were only subtle differences in the metabolic profile as a function of dose size, sex and species. An additional minor polar metabolite was excreted by male rats and mice, and the parent acids of the glycine conjugates were excreted at the higher doses. The results are discussed in terms of the participation of xenobiotics in the chain elongation reactions of fatty acid biosynthesis.

Efflux of inorganic phosphate from rat hepatocytes: lack of effect of insulin.

Efflux of Pi from rat hepatocytes suspended in phosphate free-medium was studied by chemical assay of released Pi and by monitoring the loss in radioactivity of cells pre-labelled with [32P]-Pi. The release follows first-order kinetics fairly closely with a rate constant of 7 x 10(-3) min-1 approximately. Insulin at a concentration of 10(-8) M had no effect on the rate of Pi release and it is concluded therefore, that the insulin-stimulated accumulation of Pi described in the literature is the result of hormone action on Pi uptake by liver rather than on its release.