METABOLIC-FATE AND DISPOSITION OF 1,1,1,2-TETRAFLUOROETHANE (HFC134A)IN RAT FOLLOWING A SINGLE EXPOSURE BY INHALATION

1. The metabolic fate and disposition of [U-C-14]-1,1,1,2-tetrafluoroe thane ([U-C-14]-HFC134a) has been determined in the male and female ra t following a 1 h single exposure by inhalation to atmospheres of 10 0 00 ppm. 2. Of the inhaled dose, approx. 1% was recovered in urine, fae ces and expired air postexposure indicating that absorption of this fl uorocarbon across the lung is poor. Of this 1%, approx. two-thirds wer e exhaled within 1 h of the cessation of exposure as unchanged HFC134a . The remaining radioactivity was exhaled as [C-14]-carbon dioxide or excreted in urine and faeces as trifluoroacetic acid. 3. Carbon dioxid e was the major metabolite of HFC134a accounting for 0.22 and 0.27% of the inhaled dose in the male and female rat, respectively. Urinary ex cretion accounted for 0.09% of the dose and faecal excretion 0.04% of the dose by both sexes. 4. Total metabolism measured as the sum of the radioactivities in urine, faeces and as carbon dioxide amounted to 0. 34 and 0.40% of the inhaled dose in male and female, respectively. 5. There were no major sex differences in the rates, routes or amounts of radiolabel excreted. Analysis of a range of tissues at 5 days postexp osure showed a relatively uniform distribution of radioactivity. There was no evidence for a specific uptake of HFC134a or a metabolite into any organ or tissue analysed, including fat.