Jack L. Radomski

Bladder cancer induction by aromatic amines: role of N-hydroxy metabolites.

Repeated installation of N-hydroxy-2 naphthylamine into dog bladders produced tumors of this organ. There is a correlation of degree of carcinogenicity of 1-naphthylamine, 2-naphthylamine, and 4-aminobiphenyl with both methemoglobin production in the blood and concentration of N-oxidation products in the urine. Thus, N-hydroxylation appears to be the key to bladder cancer production by aromatic amines.

Nitrosamine Formation in Bladder Infections and its Role in the Etiology of Bladder Cancer

Dimethylnitrosamine, a powerful carcinogen, is produced in the urine of patients with urinary tract infections of Proteus mirabilis and Escherichia coli when nitrite is present. Treatment with tetracycline antibiotics does not enhance the concentration of this carcinogen but, rather, sharply reduces it. The results emphasize the importance of proper antibiotic therapy for the infections to reduce the possibility of the subsequent development of bladder cancer.

N-Glucuronidation of N-hydroxy aromatic amines: a mechanism for their transport and bladder-specific carcinogenicity.

Abstract Glucuronide conjugates of carcinogenic N -hydroxy metabolites of the primary aromatic amines, 4-aminobiphenyl (4-ABP), 2-naphthylamine (2-NA), and 1-naphthylamine (1-NA) were isolated from the urine of dogs administered the respective primary amine and from the in vitro incubation of N -hydroxy metabolites with uridine-5′-disphosphoglucuronic acid-fortified dog liver microsomes. The urinary and microsomal conjugates were purified by several sequential chromatographic procedures, including Sephadex G-15, Amberlite XAD-2, and cellulose CF-11 chromatography for microsomal conjugates and Sephadex G-10, DEAE, and Amberlite XAD-2 chromatography for urinary conjugates. The infrared spectra of purified urinary and microsomal conjugates of these three N -hydroxy aromatic amines were identical to spectra of authentic NC glucuronides prepared by two different synthetic procedures. The urinary and microsomal conjugates comigrated with synthetic NC glucuronides in two solvent systems. These observations in conjunction with previous studies provide evidence that NC glucuronidation represents a general metabolic reaction of carcinogenic N -hydroxy aromatic amines which provides the means of transport of these compounds to their site of action in the bladder.

Synergism among oral carcinogens. I. Results of the simultaneous feeding of four tumorigens to rats.

Abstract A mixture of four substances, namely, Aramite, methoxychlor, DDT, and thiourea was fed to rats at a level of 50 ppm of each in the diet for a period of 24 months. This dietary concentration is considerably below the tumorigenic dosage of each of the individual compounds. Compared to the control rats, a somewhat increased incidence of liver tumors was observed in the males, and to a lesser extent the females, given the combination of the compounds. The incidences of tumors at other sites in the control and treated groups were not markedly different. A second experiment was performed using a larger number of rats in which the same four compounds were fed individually as well as in combination, at a higher dietary level (80 ppm). In this experiment the incidence of tumors of all types in the rats fed the mixture of four tumorigens was no higher than that in the rats fed single tumorigens. No liver tumor was observed in any rat receiving any of these compounds. Thus, it would seem that these four compounds do not exert a synergistic or additive tumorigenic effect when fed to rats at the levels employed.

Human pesticide blood levels as a measure of body burden and pesticide exposure

Abstract Studies have been conducted on the variability and utility of whole blood and plasma organochlorine pesticide concentration measurements in man. Concentrations of p,p′-DDE, dieldrin, and β-hexachlorocyclohexane are remarkably consistent throughout the day. Minor increases in p,p′-DDE and p,p′-DDT serum concentrations were observed promptly following the ingestion of the evening meal. In random autopsy specimens, good correlations were found between blood and fat concentrations of p,p′-DDE, p,p′-DDT, and β-hexachlorocyclohexane (β-HCH). The concentrations of these insecticides in plasma, when measured in 5 individuals repeatedly throughout a work week, were also remarkably consistent. Plasma pesticide measurements are preferred to whole blood measurements. Compared to United States residents, markedly elevated blood concentrations of β-HCH were observed in graduate students and postdoctoral fellows who had come from Formosa and Japan. Apparently, concentrations of organochlorine pesticides in the blood are in equilibrium with those in the tissue and measurement constitutes a highly useful and readily obtainable means of estimating body burdens and exposure.

Concentrations of nitrate in normal human urine and the effect of nitrate ingestion

Abstract A method suitable for the analysis of nitrate in human urine was developed. Normal urinary concentrations of nitrate in urine of human volunteers in Dade County, Florida, where the drinking water contains negligible amounts of nitrate, averaged 47.6 ppm of NO 3 − (SD = 17.3). On a vegetable and preserved-meat-free diet, the nitrate concentration was reduced (10 to 30 ppm of NO 3 − ), but, on nitrate-supplemented drinking water, the urinary concentration rose to a range of 34–87 ppm of NO 3 − . A high vegetable diet resulted in peak urinary nitrate concentrations of 270–425 ppm. These results indicated that nitrate in drinking water is a factor in determining urinary nitrate concentration, but that vegetable ingestion is of greater significance.

Blood levels of organochlorine pesticides in Argentina: occupationally and nonoccupationally exposed adults, children and newborn infants.

Abstract Determination of the concentration of organochlorine pesticides has been made in adults, children, newborn infants, and various groups of occupationally exposed individuals in Argentina. β-HCH levels in adults in Argentina are approximately 16 times higher, on the average, than the levels of β-HCH found in the U.S. In contrast, the concentrations of p,p′ -DDE, dieldrin, and p,p′ -DDT are closely similar to those in the U.S. Concentrations of β-HCH in children in Argentina are lower, but still higher than in adults in the U.S., and much higher than in U.S. children. Pesticide levels in workers handling HCH were extremely high, as were the levels of DDT and isomers in those occupationally exposed to this pesticide. No dieldrin was detected in these workers—a possible indication that microsomal stimulation by DDT may have been responsible for clearing the tissues. The DDE:DDT ratio appeared to be an accurate measurement of a recent exposure to DDT. Pesticides passed the placental barrier, but transmission was apparently somewhat retarded. Concentrations of p,p′ -DDE, p,p′ -DDT, dieldrin, and β-HCH in the newborn were approximately 40% of the pesticide concentration in the blood of the mother. This percentage was higher for α-HCH, and lindane.

The role of N-oxidation products of aromatic amines in the induction of bladder cancer in the dog

Highly sensitive gas chromatographic methods for the determination of the N-hydroxy and nitroso derivatives of 1- and 2-naphthylamine, and 4-amino-biphenyl in urine have been developed. Dogs given a single oral 70 mg/kg dose of 1-naphthylamine were found to excrete almost as much of these N-oxidation products as dogs given the same dose of 2-naphthylamine. However, when 5 mg/kg of 2-naphthylamine was given, a total of approximately 0.2% of the administered dose was found in the urine as N-oxidation products, while the same dose of 1-naphthylamine produced only faint traces. The N-oxidation products present were 2-naphthylhydroxylamine and 2-nitrosonaphthalene. In addition, blood methemoglobin production, a measure of the level of N-hydroxylation occurring, observed with 2-naphthylamine was much greater than with 1-naphthylamine at the 70 mg/kg dose. 4-Aminobiphenyl, the most potent carcinogen, produced even higher levels of N-oxidation products in the urine and blood methemoglobin than 2-naphthylamine. These results indicate that N-oxidation may be a key process in the production of bladder cancer by 2-naphthylamine and 4-aminobiphenyl.ZusammenfassungHochempfindliche gaschromatographische Methoden zur Bestimmung der N-Hydroxy- und -nitrosoderivate von 1- und 2-Naphthylamin und 4-Aminobiphenyl im Harn wurden entwickelt. Hunde schieden nach einer einzelnen oralen Dosis von 70 mg/kg 1-Naphthylamin ebenso viel N-Oxydationsprodukte aus wie Hunde nach der gleichen Dosis 2-Naphthylamin. Werden jedoch 5 mg/kg 2-Naphthylamin verabfolgt, findet man insgesamt ungefähr 0,2% der verabfolgten Dosis als N-Oxydationsprodukte im Harn, während die gleiche Dosis 1-Naphthylamin nur geringe Spuren erzeugt. Die gefundenen N-Oxydationsprodukte waren 2-Naphthylhydroxylamin und 2-Nitrosonaphthalm. Außerdern war die Bildung von Methämoglobin im Blut, ein Maß für die stattfindende N-Hydroxylierung, bei 2-Naphthylamin viel größer als bei 1-Naphthylamin nach der Dosis von 70 mg/kg. 4-Aminobiphenyl, das stärkste Karzinogen, erzeugte noch höhere Spiegel an N-Oxydationsprodukten im Harn und Methämoglobin im Blut als 2-Naphthylamin. Diese Ergebnisse weisen auf die N-Oxydation als einen Schlüsselprozeß bei der Erzeugung von Blasenkrebs durch 2-Naphthylamin und 4-Aminobiphenyl hin.

CHRONIC TOXICITY STUDIES ON IRRADIATED BEEF STEW AND EVAPORATED MILK.

Abstract Beef stew (C-ration) and evaporated milk, irradiated at levels of 2.79 and 5.58 megarads were fed to rats and to dogs as 35% of their diets for a period of two years. Fat-soluble vitamins were administered separately to both species. Nonirradiated beef stew and evaporated milk of similar origin were used as the controls. Simultaneously, a breeding study was carried out in which the rats fed the irradiated foods were bred through four generations. A breeding experiment was also conducted on both rats and dogs. The urine of dogs was examined for protein casts and reducing substances. After two years of feeding, all animals were sacrificed and thorough histopathologic studies were performed on 24 tissues of each animal. No indication of any toxic effect due to the feeding of either irradiated food either in the longevity or the breeding phases of these experiments was obtained.

Synthesis of the urinary glucuronic acid conjugate of N-hydroxy-4-aminobiphenyl.

The glucuronic acid conjugate of N-hydroxy-4-aminobiphenyl believed to be the carrier form responsible for transporting the active N-hydroxy compound from its site of formation in the liver to its site of carcinogenic action in the bladder has been prepared synthetically. The synthetic conjugate is identical by infrared and chromatographic analyses with the conjugate isolated from urine, thus unequivocally establishing its structure as an N--C conjugate, sodium (N,4-biphenyl-N-hydroxy-D-glucuronosylamine).