EFFECT OF OVARIECTOMY ON THE IN-VITRO AND IN-VIVO ACTIVATION OF CARCINOGENIC N-2-FLUORENYLHYDROXAMIC ACIDS BY RAT MAMMARY-GLAND AND LIVER

N-Hydroxy-N-2-fluorenylacetamide (N-OH-2-FAA) and its benzamide analog ue N-OH-2-FBA are mammary gland carcinogens in the female Sprague-Dawl ey rat. Ovariectomy inhibits tumorigenicity of topically applied N-OH- 2-FAA suggesting modulation of carcinogen-activating enzymes in the gl and. This study concerned the activation of N-OH-2-FAA and N-OH-2-FBA by the mammary gland and liver, a chief site of metabolism, from 50-da y-old female rats and effects on the activation of ovariectomy perform ed at 22 days of age. The levels of N-debenzolyation of N-OH-2-FBA to N-hydroxy-N-2-fluorenamine (N-OH-2-FA), catalyzed by microsomal carbox yl-esterases in mammary gland and liver were similar and increased 1.5 - and 1.7-fold, respectively, by ovariectomy. N-Debenzoylating activit y in cytosols of both tissues appeared to be partially of microsomal o rigin, Mammary gland cytosol contained N-, O- and N,O-acyltransferase activities at levels 40-50% those of liver, N-Acyltransferase activity was determined via acetyl coenzyme A (AcCoA)-dependent acetylation of 2-FA and a new assay, N-OH-2-FAA-dependent acetylation of 9-oxo-2-FA. The latter activity was decreased in mammary gland by ovariectomy, Mi crosomal N-acyltransferase activities were <36% those of cytosols, AcC oA-dependent binding of N-OH-2-[ring-H-3]FBA to DNA, catalyzed by cyto sol, was consistent with a two-step activation of N-OH-2-FBA involving esterase-catalyzed N-debenzoylation to N-OH-2-FA and its O-acyltransf erase-catalyzed acetylation to the electrophilic N-acetoxy-2-FA. O-Ace tyltransfer by mammary gland appeared to be rate-limiting since ovarie ctomy-dependent increases in N-debenzoylation did not increase binding with S9 fraction. Little or no sulfotransferase-catalyzed binding of N-OH-2-[ring-H-3]FBA-derived N-OH-2-[ring-H-3]FA was detected in the l iver or mammary gland cytosol, respectively. The level of binding of N -OH-2-[ring-H-3]FAA to DNA catalyzed by cytosolic N,O-acyltransferase was decreased similar to 23% in mammary gland and increased 1.2-fold i n liver by ovariectomy, P-32-Postlabeling analyses indicated a single adduct N-(deoxyguanosin-8-yl)-2-fluorenamine in DNA of both tissues 24 h after one intraperitoneal injection of N-OH-2-FBA or N-OH-2-FAA. Re spective levels were 3.6- and 5.5-fold greater in liver than mammary g land, After ovariectomy, the adduct levels from N-OH-2-FBA increased 1 .8-fold in mammary gland and from N-OH-2-FAA decreased similar to 50% in both tissues, Thus, the ovariectomy-dependent changes in levels of enzymes activating N-OH-2-FBA and N-OH-2-FAA were consistent with in v ivo DNA adduct levels in the target mammary gland, but not in the live r.