Enzymatic acetylation and sulfation of N-hydroxyarylamines in bacteria and rat livers

Abstract

In mammalian hepatic cytosol both acetyltransferase and sulfotransferase are involved in the activation of N-hydroxy derivatives of arylamines and arylamides. The role of acetyltransferase is also shown in Salmonella, whereas no rigid evidence is provided on the role of sulfotransferase in Salmonella. In Ames mutagenesis test without S9-mix, the number of revertants of Salmonella typhimurium TA98 induced was 10-fold higher with 2-hydroxyamino-3-methylimidazo[4,5-f] quinoline (N-hydroxy-IQ) than with 2-hydroxyamino-6-methyldipyrido[1,2-a:3',2'-d]imidazole (N-hydroxy-Glu-P-1). The extents of the binding to calf thymus DNA of N-hydroxy-Glu-P-1 were, however, 3.9 to 8.6-fold higher than that of N-hydroxy-IQ in both acetyl CoA- and PAPS-fortified rat hepatic cytosol systems. To understand the mechanism causing the apparent discrepancy between the results of the mutation and DNA binding, the activating capacities of cytosols of S. typhimurium TA98 and TA98/1,8-DNP6 strains on the binding of N-hydroxy-Glu-P-1 and N-hydroxy-IQ have been examined in comparison with those of rat livers. Although both N-hydroxyarylamines were activated by hepatic cytosols in the presence of PAPS, no significant DNA binding of these N-hydroxyarylamines was detected in the presence of PAPS and either one of the two strains of bacterial cytosols. In addition, both cytosols of TA98 and TA98/1,8-DNP6 strains showed no measurable activity on the sulfation of p-nitrophenol, suggesting no capacity for sulfotransferase-mediated activation of N-hydroxyarylamines in Salmonella. On the contrary, the extents of the acetyl CoA-dependent binding of N-hydroxy-IQ in cytosols of TA98, but not of TA98/1,8-DNP6, were respectively 6- and 9-fold higher than those in hepatic cytosols of male and female rats, although the extents of the binding of N-hydroxy-Glu-P-1 were rather higher in hepatic than in bacterial cytosols. In addition, the covalent binding of N-hydroxy-2-acetylaminofluorene to DNA was detected in hepatic, but not in bacterial cytosols, although the binding of N-hydroxy-2-aminofluorene was detectable in both hepatic and bacterial cytosols in the presence of acetyl CoA. These results indicate that the metabolic activating capacities of Salmonella and rat liver cytosols differ qualitatively, and the difference in the substrate specificity of acetyltransferase between Salmonella and rat livers may be involved, in part, in the difference of their DNA damage in bacteria and mammals.

Self-augmentation Effect of Male-specific Products on Sexually Differentiated Progesterone Metabolism in Adult Male Rat Liver Microsomes

“…§, the magnitudes of sexually differentiated enzyme activities in adult male rat liver, compared with the female, are as follows: CYP2C11 (Ͼ30-fold higher) (1-3, 9), CYP3A2 (Ͼ20-fold higher) (1, 9), 5␣-reductase (ϳ10-fold lower) (2, 3, 7), 3␣-hydroxysteroid dehydrogenase (2-3-fold lower) (27, 28), UDP-glucuronosyl transferase (ϳ1.5-fold higher) (29), and hydroxysteroid sulfotransferase (4 -6-fold lower) (30,31). The experimental conditions were the same as shown in Fig.…”

“…In some cases, before the above described incubation procedure, microsomal suspension (250 g of protein/1.1 ml, total volume of the reaction mixture) was preincubated with goat anti-rat NADPH P450 reductase antiserum (50 l) at 25°C for 30 Miscellaneous Methods-Other procedures are described in our previous papers (11)(12)(13). Table I.…”

Growth Hormone Activation of Stat 1, Stat 3, and Stat 5 in Rat Liver

“…Anti-Stat 3 detected tyrosinephosphorylated and nonphosphorylated Stat 3 (bands marked 3(P) and 3, respectively) as well as an additional unidentified band (*) in the intact nuclear extracts, which may correspond to the recently described Stat 3␤ (71), whereas only band 3(P) was detected following immunoprecipitation (B). Several nonspecific bands seen on the anti-Stat 5 blot were removed by immunoprecipitation (C, lanes 5-9 versus lanes [1][2][3][4]. D and E, Western blot of nuclear extracts prepared from hypophysectomized male (M) rats given the treatments indicated, analyzed either with (lanes 10 -13) or without (lanes 14 and 15) antibody 4G10 immunoprecipitation, and probed sequentially with anti-Stat 3 and anti-Stat 5, as indicated.…”

“…GH exerts both stimulatory and inhibitory effects on the expression of a wide range of liver gene products, including cytochrome P450 (1, 2), glutathione S-transferase (3), and sulfotransferase enzymes involved in steroid and drug metabolism (4), in addition to several cellsurface receptors (5,6), including GH receptor (7). Hepatic secretory products, such as insulin-like growth factor 1, serine protease inhibitor Spi 2.1 (8), and various urinary proteins (9,10), are also expressed in a GH-dependent manner.…”

Epigallocatechin Gallate (EGCG) Inhibits the Sulfation of 1-Naphthol in a Human Colon Carcinoma Cell Line, Caco-2.

“…1) Bioactivation of carcinogenic arylamine and heterocyclic amine metabolites by mammalian liver phenol sulfotransferases (P-STs) has been postulated as a key mechanism leading to aromatic carcinogenesis in humans. [2][3][4][5] To elucidate whether the anti-carcinogenic activity of green tea is related to ST activity, we previously investigated the effect of green tea on P-ST activity in the mouse intestine and in a human colon carcinoma cell line, Caco-2. We found that catechins, especially epigallocatechin gallate (EGCG), strongly inhibit in vitro P-ST activity in both types of cells.…”