Observations on the Metabolism of N-2-Fluorenylacetamide in Dogs and Rats,

Summary

With colorimetric methods for comparison of the excretion of metabolites of N-2-fluorenylacetamide (2-FAA) by rats and dogs, less diazotizable material was recovered from the urine of dogs than from rats. Paper chromatography of ether extracts of β-glucuronidase and Taka-diastase-digested urine confirmed published observations that rats excrete numerous ring-hydroxylated metabolites of 2-FAA as well as N-hydroxy-2-FAA, chiefly as glucuronides. N-hydroxy-2-FAA, 7-hydroxy-2-FAA and 7-hydroxy-2-FA glucuronides, unconjugated 7-hydroxy-2-FAA, and small amounts of 2-FAA were identified in ether extracts of the urine of four dogs. Recoveries of diazotizable metabolites accounted for 55 percent of the average recovery of radioactivity from rats' urine after a single dose of 2-FAA-9-C ¹⁴. For dogs recoveries from urine by the colorimetric methods approximately equaled those reported elsewhere for radioactivity. This difference in recoveries of urinary metabolites from rats and dogs by the colorimetric methods compared with radioactivity recoveries may be explained by the fact that many of the ring-hydroxy metabolites in the rat are not measurable by the colorimetric methods, whereas the metabolites in the urine of dogs react more nearly quantitatively, provided the urine has not been subjected to hydrolysis. However, dogs' urine, unlike that of rats, after a dose of 2-FAA, contained a considerable amount of diazotizable R-salt-reacting free amines, including one or more that were unstable after digestion of the urine with ×-glucuronidase. It has been postulated that part, if not all of the unstable amine(s) may be N-hydroxy-2-FA. Acetylation of the urine or hydrochloric-acid-extracted free amines from dogs' urine revealed no metabolites of 2-FAA except N-hydroxy-2-FAA and 7-hydroxy-2-FAA.