Aryl sulfotransferase IV deficiency in rat liver carcinogenesis initiated with diethylnitrosamine and promoted with N-2-fluorenylacetamide or its C-9-oxidized metabolites.
Down regulation of aryl sulfotransferase IV (AST IV) in promotion/progression of liver carcinogenesis by N-2-fluorenylacetamide (2-FAA) has been established. This study examined whether the C-9 oxidized metabolites of 2-FAA, which have recently been shown to promote diethylnitrosamine (DEN)-initiated liver carcinogenesis in male Sprague-Dawley rats, effect the above change. Hence, in DEN-initiated rats, the effects of promoting regimens of 9-OH-2-FAA or 9-oxo-2-FAA, 15 oral doses at 50 and 100 mumol/kg of body weight, were compared to those of 2-FAA at 50 mumol/kg of body weight and of the vehicle on the activity of N-hydroxy(OH)-2-FAA sulfotransferase (ST), an isozyme of AST IV and AST IV expression and distribution. Relative to the vehicle, treatment with the fluorenyl compounds led to decreased levels in hepatic N-OH-2-FAA ST activity and development of hepatic nodules and tumors which had still lower levels of the ST activity than the respective remnant livers. At approximately 8 months after treatment with the C-9-oxidized compounds at doses twice that of 2-FAA, the extents of decreases in the hepatic N-OH-2-FAA ST activity and cytosolic AST IV protein in tumors were comparable to those with 2-FAA. Immunocytochemical analysis showed close association of AST IV deficiency with neoplastic liver lesions. In comparison to N-OH-2-FAA, 9-OH-2-FAA had only low and 9-oxo-2-FAA lacked sulfate acceptor activity in the presence of male rat liver cytosol or AST IV. At 3.3-fold greater concentration than N-OH-2-FAA, 9-oxo-2-FAA inhibited (27%) the sulfate acceptor activity of N-OH-2-FAA in the presence of AST IV, which suggested interference by 9-oxo-2-FAA at the active site. Although the C-9-oxidized compounds do not appear to be substrates for N-OH-2-FAA ST, their ability to cause a decrease in N-OH-2-FAA ST activity and protein similar to that of 2-FAA supports their role in hepatocarcinogenesis. Whereas 9-OH-2-FAA had a 3.9-fold greater sulfate acceptor activity in the presence of female than male rat liver cytosol and inhibited dehydroepiandrosterone ST activity of female rat liver, N-OH-2-FAA and 9-oxo-2-FAA inhibited estrone ST activity of male rat liver, suggesting that the C-9-oxidized compounds as well as N-OH-2-FAA are substrates for STs other than AST IV.
Malejka-Giganti
D
D
Veterans Affairs Medical Center, Mineapolis, Minnesota 55417, USA.
Ringer
D P
DP
Vijayaraghavan
P
P
Kiehlbauch
C C
CC
Kong
J
J
D015073:2-Acetylaminofluorene / Q000031:analogs & derivatives / Q000378:metabolism / Q000633:toxicity*; D000818:Animals; D015239:Arylsulfotransferase / Q000172:deficiency* / Q000378:metabolism; D002273:Carcinogens / Q000378:metabolism / Q000633:toxicity*; D004052:Diethylnitrosamine / Q000633:toxicity*; D015536:Down-Regulation; D004357:Drug Synergism; D005260:Female; D007527:Isoenzymes / Q000172:deficiency* / Q000378:metabolism; D008099:Liver / Q000187:drug effects / Q000201:enzymology; D008113:Liver Neoplasms / Q000139:chemically induced / Q000201:enzymology*; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D013431:Sulfates / Q000378:metabolism
D002273:Carcinogens; D007527:Isoenzymes; D013431:Sulfates; D004052:Diethylnitrosamine; D015073:2-Acetylaminofluorene; D015239:Arylsulfotransferase