Mutagenic activity of carcinogenic and noncarcinogenic nitrofurans and of urine of rats fed these compounds

The nitrofurans, 2-(2-furyl)-3-(5-nitro-2-furyl)acrylamide (AF-2), N-[4-(5-nitro-2-furyl)-2-thiazolyl]formamide (FANFT), nitrofurantoin, 5-nitro-2-furoic acid, 5-nitro-2-furamidoxime, 5-nitrofurfurylidene diacetate and the urine of rats fed these compounds, were assayed for mutagenic activity in Salmonella typhimurium strains TA100 and TA100FR1. All the nitrofurans were mutagenic in the order: AF-2 and FANFT greater than nitrofurantoin greater than 5-nitro-2-furamidoxime greater than 5-nitrofurfurylidene diacetate greater than 5-nitro-2-furoic acid. Strain TA100 was more sensitive than TA100FR1 to the mutagenic influence of these nitrofurans. Only the urine of rats fed AF-2, FANFT and nitrofurantoin had mutagenic activity. Again, TA100 was more sensitive than TA100FR1. The mutagenicity of the urine was not increased by treatment with beta-glucuronidase. AF-2, 2-amino-4-(5-nitro-2-furyl)thiazole (deformylated product of FANFT) and nitrofurantoin were excreted in the urine of rats fed these compounds; whereas the other nitrofurans were not excreted.

A simple method for detection and analysis of carcinogenic nitrofuran compounds and their metabolites by combining chromatography and spot mutation tests

A simple, sensitive, and convenient method combining thin-layer chromatography and a spot test for mutagenicity of Salmonella typhimurium TA100 was utilized for the analysis of urine of rats fed N-[4-(5-nitro-2-furyl)-2-thiazolyl]-formamide (FANFT), a potent experimental urinary bladder carcinogen. Three metabolites of FANFT were detected in urine, and one of these, accounting for 33% of the urinary metabolites of FANFT, was identified as 2-amino-4-(5-nitro-2-furyl)thiazole (ANFT). ANFT was the only urinary metabolite that clearly demonstrated mutagenic activity, suggesting that ANFT may be a proximate vesical carcinogen of FANFT.

Studies with B-cell allo- and hetero-antisera: parallel reactivity and special properties

The expression of B-cell antigens on various cell populations was studied through the use of human alloantisera and with heteroantisera raised to preparations of the alloantigen bearing molecules isolated from B-cell lines. The allo-and hetero-antisera competed with each other in blocking experiments and gave closely parallel results, reacting with normal and leukemic B lymphocytes, monocytes, E-rosette-negative acute lymphatic leukemias, all acute and certain chronic myelogenous leukemias, and a minor population of cells in fetal spleen and liver. These highly immunogenic surface components appeared to comprise the dominant B- cell specific plasma membrane determinants. Neither type of antiserum reacted with any but a minor population of normal or pokeweed-mitogen-transformed T cells, fetal thymic lymphocytes, E-rosette-positive acute lymphatic leukemias, or Sezary-cell leukemia. Through the use of these antisera evidence was obtained that Fc-receptor-bearing Ig-negative lymphocytes were divisible into two groups according to the presence or absence of the B-cell antigens. Both hetero- and allo-antisera blocked binding of immune complexes or antibody-coated ox erythrocytes to Fc receptors on B cells. F(ab')2 fragments of the heteroantibodies strongly inhibited antibody-dependent cell-mediated killing.

Enhancing effect of allopurinol on the induction of bladder cancer in rats by n-[4-(5-nitro-2-furyl)-2-thiazolyl]formamide

The effects of allopurinol on the induction of bladder cancer by N-[4-(5-nitro-2-furyl)-2-thiazolyl]formamide (FANFT), excretion of urinary tryptophan metabolites, hepatic nitroreductase activity, and the acid-soluble thiol content of liver and blood in weanling female Fischer rats were investigated. Four groups of rats were given normal diet or normal diet supplemented with 0.005% allopurinol, 0.188% FANFT, or 0.005% allopurinol-0.188% FANFT. Transitional cell carcinomas appeared in 3 of 30 rats (10%) at 15 weeks and in 7 of 44 rats (16%) at 20 weeks in the FANFT-treated group; the carcinomas appeared in 14 of 35 rats (40%) at 15 weeks and in 27 of 50 rats (54%) at 20 weeks in the FANFT-allopurinol-treated group. Growth rate was not affected by allopurinol and FANFT. Allopurinol alone caused no morphological change in the epithelial cells of the urinary bladder but decreased hepatic cytosol nitroreductase activity. FANFT alone had no effect on hepatic cytosol or microsomal nitroreductase activity but increased hepatic and blood acid-soluble thiol content. FANFT increased the urinary excretion of anthranilic acid glucuronide, kynurenine, acetylkynurenine, and 3-hydroxykynurenine and decreased indican and o-aminohippurate excretion. Allopurinol did not alter the effects of FANFT on the acid-soluble thiol content of liver and blood or the excretion of urinary tryptophan metabolites.

Identification of carcinogenic tannin isolated from Bracken fern (Pteridium aquilinum)

We attempted to isolate a carcinogenic substance from bracken fern (Pteridium aquilinum), a naturally occurring toxicant responsible for the production of chronic enzootic hematuria and urinary bladder cancer of cattle and carcinogenic for various target organs of several species. Hot methanol extracts of bracken fern were solubilized in water and extracted with chloroform followed by a mixture of n-butanol-butanone (1:1). That fraction was dried and triturated with ether-methanol (4:1), n-butanol, and finally absolute ethanol. The insoluble residue was dissolved in 10% aqueous methanol and passed through Dowex 1 OH-, Dowex 50 H+, or Dowex 1 OH- and then Dowex 50 H+ ion exchange resins. A condensed tannin, isolated from one ot the fractions, was identical to that isolated from bracken fern by the caffeine procedure used for the separation of tannins from other plant constituents. Three systems were used for bioassay; induction of bladder carcinoma by implantation of cholesterol pellets containing bracken fern fractions into the bladder lumens of mice; acute toxicity by ip injection of brachen fern fraction into mice; and growth inhibition of Escherichia coli. The following fractions induced significantly greater incidences of bladder carcinoma than did cholesterol pellets only: tannin, Dowex 50 H+, residue, n-butanol, and methanol. Tiliroside, a component of bracken fern fractions into the bladder lumens of mice; acute genic acid, and quercetin were not carcinogenic. Tannin was the most toxic (mean lethal dose: 0.16 mg/g) and carcinogenic. None of the carcinogenic fractions inhibited growth of E. coli.

Mutagenicity of nitrofurans, nitrothiophenes, nitropyrroles, nitroimidazole, aminothiophenes, and aminothiazoles in Salmonella typhimurium

Thirty-two heterocyclic compounds, including 24 nitroheterocycles, 7 aminoheterocycles and derivatives, and 1 thiophene lacking a nitro group, were tested for mutagenic activity in Salmonella typhimurium TA 98 and TA 100. All the nitroheterocycles (11 new), including nitrofurans, nitrothiophenes, nitropyrroles, and 1 nitroimidazole, were mutagenic in TA 100; 13 were also mutagenic in TA 98. 5-Nitro-2-furoic acid, a noncarcinogen, was mutagenic in TA 100. Seven carcinogenic nitroheterocycles were mutagenic in both strains. Seven aminoheterocycles (4 new), aminothiophenes and aminothiazole derivatives, and 1 thiophene without a nitro group were not mutagenic. Both TA 98 and TA 100 were uvrB and lacked the ability of excision repair of DNA. Among the 24 mutagenic nitroheterocycles, only 13 compounds exhibited bacterial killing effects, suggesting that more than 1 mechanism may be involved in the interaction of nitroheterocycles with bacterial DNA.

Studies of native plants in Taiwan for lectin content

The lectin content of some native plants in Taiwan was studied. The majority of the plants possessing lectin belonged to Leguminosae. Five lectins which are readily available were further studied for their hemagglutination titers, specificity, susceptibility to heat and proteolytic enzymes. The lectins of Ricinus communis had hemagglutination titer of 1:512 which was the highest among the five tested. All lectins were heat labile, destroyed by heating at 100 degrees C for 30 min, but resistant to trypsin and pepsin. The resistance was not due to the presence of any inhibitor in the crude extract, but possibly due to the special configuration of the lectin molecule or other unknow reasons. Among the five lectins only the lectin of Phaseolus vulgaris could not be inhibited by any of the carbohydrates tested. It seems that the lectin of Phaseolus vulgaris is nonspecific, or not specific for ABO blood group, or specific for other blood groups. The inhibiting activity of carbohydrates seems to be specific. The configuration of carbohydrates at carbon atom 2 and/or 4, the type of linkage (alpha or beta), or the carbon number where the linkage is formed seem to be important to the potency of carbohydrates to inhibit the activity of lectin.

Antibacterial activity of nitropyrroles, nitrothiphenes, and aminothiophenes in vitro

The antibacterial activities of nitropyrroles, nitrothiophenes, and aminothiophenes were studied. Replacement of the nitro group with an amino group enhanced the activity of the thiophene compounds.

Metabolism and disposition of N-(4-(5-nitro-2-furyl)-(2-14-C)thiazolyl)acetamide in the rat

The metabolism of N-[4-(5-nitro-2-furyl)-2-thiazolyl]acetamide (NFTA), a carcinogen for the mouse, rat, dog, and hamster, was investigated in the rat. Radioactive NFTA administered ip to young and lactating female rats was rapidly absorbed through the peritoneum and deposited in the urine, intestinal contents, and feces. Less than 0.5% of the radioactivity was expired as CO2 during the first 24 hr. Two yellow metabolites, accounting for 5 and 27% of the radioactivity in the urine, were found by paper chromatography. One metabolite retained the 2-amino-4-(5-nitro-2-furyl)thiazole moiety. Less than 0.5% of the radioactivity in the urine was due to unchanged 14-C-NFTA. The radioactivity level in the visceral organs reached a maximum 2 hr after dosing and then gradually decreased. Liver contained considerably more radioactivity than did other visceral organs; this was mainly distributed in the cytosol and 900g pellets. Fifty per cent of the radioactivity in the liver was bound to the hot trichloroacetic acid (TCA)-insoluble fraction; that bound to the cold TCA-insoluble fraction increased gradually from 66.9% at 2 hr to 82.6% at 24 hr. The radioactivity bound to the cold and hot TCA-insoluble fractions in kidney remained at 30% and 20%, respectively. Nitroreduction of 14-C-NFTA by microsomes, as a prerequisite of the binding of metabolite to microsomal protein, was demonstrated. Addition of L-cysteine or reduced glutathione to the incubation mixture did not alter the nitroreductase activity of the microsomes; however, binding of radioactivity to protein was significantly decreased. Addition of other amino acids did not significantly decrease the nitroreductase activity or binding to protein. These results suggest that reduced NFTA binds to the protein sulfhydryl groups. Since 14-C-NFTA binds to macromolecules in vivo,nitroreductionmay be important for the metabolism of 5-nitrofurans.