ACTIVATION OF THE CARCINOGENS N-HYDROXY-N-2-FLUORENYLBENZAMIDE AND N-HYDROXY-N-2-FLUORENYLACETAMIDE VIA DEACYLATIONS AND ACETYL TRANSFERS BY RAT PERITONEAL SEROSA AND LIVER

Intraperitoneally administered N-hydroxy-N-2-fluorenylbenzamide (N-OH- 2-FBA) and N-hydroxy-N-2-fluorenylacetamide (N-OH-2-FAA) are carcinoge nic for rat peritoneum. The potential of peritoneal serosa to activate these compounds via deacylations and acyl transfers was compared to t hat of liver. N-Deacylations of N-OH-2-FBA and N-OH-2-FAA to N-2-fluor enylhydroxylamine (N-OH-2-FA) were faster by liver than serosa and by microsomes than cytosols. N-Debenzoylations of N-OH-2-FBA were 73- to 123-fold faster than N-deacetylations of N-OH-2-FAA. The esters, N-ben zoyloxy-2-FBA and N-acetoxy-2-FAA, were O- and N-deacylated to N-OH-2- FA by liver, and the benzoate by serosa. Inhibition by paraoxon of the above deacylations implicated a serine carboxylesterase. Liver and se rosa cytosols catalyzed acetyl CoA-, but not benzoyl CoA-, dependent a nd iodoacetamide (IAA)-sensitive N-acylation of N-2-fluorenamine (2-FA ), implicating an acetyltransferase. In hepatic microsomes this activi ty was IAA-insensitive and partially inhibited by paraoxon. Liver cyto sol, but not microsomes, used N-OH-2-FAA as an acyl donor and neither used N-OH-2-FBA. Liver and serosa catalyzed binding to DNA of N-OH-2-[ ring-H-3]FBA which was paraoxon-sensitive and increased by acetyl CoA, but not benzoyl CoA. Binding to DNA of N-OH-2-[ring-H-3]FAA catalyzed by cytosols was similar to 22-fold greater in liver than in serosa an d was IAA-sensitive. Microsome-catalyzed binding of this compound in b oth tissues was increased similar to 2-fold by acetyl CoA. The results support a two-step activation of N-OH-2-FBA in the liver consisting o f esterase-catalyzed N-debenzoylation to N-OH-2-FA and an acyltransfer ase-catalyzed O-acetylation to the putative electrophile N-acetoxy-2-F A. In the serosa, binding to DNA appears to be due to rapid N-debenzoy lation to N-OH-2-FA, a fraction of which is O-acetylated. Whereas acti vation of N-OH-2-FAA by liver and serosa microsomes may also involve N -OH-2-FA and/or its O-acetate, activation by the cytosols is consisten t with N,O-acetyltransfer of N-OH-2-FAA to yield N-acetoxy-2-FA. The s tudy provides first evidence for activation of N-OH-2-FBA by rat liver and of both compounds by peritoneum in vitro.