Metabolic fate and disposition of 1,1,1,2-tetrafluoroethane (HFC134a) in rat following a single exposure by inhalation

Abstract

1. The metabolic fate and disposition of [U-¹⁴C]-1,1,1,2-tetrafluoroethane ([U-¹⁴C]-HFC134a) has been determined in the male and female rat following a 1 h single exposure by inhalation to atmospheres of 10 000ppm.

2. Of the inhaled dose, approx. 1% was recovered in urine, faeces and expired air postexposure indicating that absorption of this fluorocarbon across the lung is poor. Of this 1%, approx. two-thirds were exhaled within 1 h of the cessation of exposure as unchanged HFC134a. The remaining radioactivity was exhaled as [¹⁴C]-carbon dioxide or excreted in urine and faeces as trifluoroacetic acid.

3. Carbon dioxide 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 excretion 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 postexposure 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.