Metabolism of three cyclic nitrosamines in Sprague-Dawley rats

The metabolism of three cyclic nitrosamines has been studied in Sprague-Dawley rats. The compounds were nitrosopyrrolidine, nitrosohexamethyleneimine, and nitrosohepatamethyleneimine and were labeled at the alpha carbon with 14C. At low doses (2 to 4 mg/animal) the compounds were metabolized to 14CO2 to the extent of 77, 43, and 27%, respectively, after 24 hr. At doses closer to the 50% lethal dose of the compounds (70 to 160 mg/animal) the metabolism values were only 14, 4, and 8%, respectively, after 24 hr. The significance of these results is discussed.