DYNAMIC MONITORING OF TOTAL-BODY ABSORPTION BY F-19 NMR-SPECTROSCOPY - ONE-HOUR VENTILATION OF HFA-134A IN MALE AND FEMALE RATS

Six male and six female Sprague-Dawley rats were ventilated head-only for 1 h on a 15% atmosphere of 1,1,1,2-tetrafluoroethane (HFA-134a) in air in a magnetic resonance imaging spectrometer. Results from these dynamic F-19 NMR studies suggest that a steady-state in vivo concentra tion of HFA-134a was approached at approximately 25 min into the expos ure. Quantitative integration analysis using an external standard esti mated this plateau to be 58.3 +/- 11.9 mg of absorbed HFA-134a per rat . The HFA-134a F-19 NMR signal disappeared rapidly following removal o f the test atmosphere, with an elimination half-life of 4.6 +/- 0.6 mi n in the male rats and 4.9 +/- 1.5 min in the female rats. The data su ggest that there was no statistical difference between the sexes in am ount absorbed or in elimination half-lives.