DNA adduct formation in Salmonella typhimurium, cultured liver cells and in Fischer 344 rats treated with o-tolyl phosphates and their metabolites

2-Phenoxy-4H-1,3,2-benzodioxaphosphorin 2-oxide is an electrophilicand a neurotoxic metabolite of o-tolyl phosphates. In a previouspaper we reported that 2-phenoxy-4H-1,3,2-benzodioxaphosphorin2-oxide is mutagenic in Salmonella typhimurium TA100 and formsDNA adducts in incubations with nucleotides, nucleosides andisolated DNA. In the present study we compare DNA adduct formationusing ³²P-post-labelling assays in 2-phenoxy-4H-1,3,2-benzodioxaphosphorin2-oxide-treated bacteria (S.typhimurium TA100) and hepatomacells with DNA adducts formed in liver, kidney, lung and heartof tri-o-tolyl phosphate-exposed Fischer 344 male rats. In bothbacteria and hepatoma cells two DNA adducts could be detectedafter treatment with 2-phenoxy-4H-1,3,2-benzodioxaphosphorin2-oxide. The minor adduct co-chromatographed with syntheticN³-(o-hydroxy-benzyl)deoxyuridine 3' monophosphate after postlabelling.The major DNA adduct was a cytidine adduct, most likely N³-(o-hydroxybenzyl)deoxycytidine3' monophosphate. Male Fischer 344 rats were treated orallyfor 10 days with tri-o-tolyl phosphate (50 mg/kg/day) and DNAwas isolated from liver, kidney, lung, heart, brain and testes1,4,7 and 28 days after giving the last dose. Analysis by ³²P-postlabellingrevealed that two adducts were present in the DNA isolated fromliver, kidney, lung and heart on the first day after givingthe last dose; DNA adducts were not detected in the brain andtestes. The adduct pattern after in vivo treatment with tri-o-tolylphosphate was identical with that found in bacteria and hepatomacells treated with 2-phenoxy-4H-1,3,2-benzo-dioxaphosphorin2-oxide, the major adduct being N³-(o-hydroxybenzyl)deoxycytidine3' monophosphate and the minor N³-(o-hydroxybenzyl)deoxyuridine3' monophosphate. Both DNA adducts persisted in the lungs forthe entire observation period, whereas in the kidney only thecytidine adduct could be detected 28 days after the last doseof tri-o-tolyl phosphate. In liver and heart the adducts weredetectable only on the first day after completion of the treatment.The results indicate that in addition to the well establishedneurotoxicity, some o-tolyl phosphates may have a carcinogenicpotential.     

Einführung

Ohne Zusammenfassung

---

Introduction

     

Trichloroethylene exposure and trichloroethylene metabolites in urine and blood

After trichloroethylene (Tri) inhalation the metabolite trichloroethanol (TCE) is excreted rapidly in the urine, while trichloroacetic acid (TCA) accumulates in the organism due to a high plasma protein binding rate. After exposure of 5 volunteers to 50 ppm Tri for 6 h, 50 g/ml TCA is found in the plasma at the end of the 5th exposure day, the amount of TCE present in the blood amounting to not more than 2.3 g/ml. Instead of the previously used control of TCE + TCA in the urine, it is suggested to determine the metabolites in the blood by means of a gas Chromatographic micro technique which provides a reliable criterion of the preceding Tri exposure.The described study was supported by the Deutsche Forschungsgemeinschaft.     

Wirkung von Trispuffer (THAM) und Natriumbicarbonat auf die metabolische Acidose bei der Methanolvergiftung des Hundes

Zusammenfassung Die aus der Oxydation von Methanol im Organismus anfallende Ameisensäure akkumuliert und führt zur metabolischen Acidose. Tris-puffer (THAM) und Natriumbicarbonat, i.v. infundiert, normalisieren in Versuchen an Hunden prompt, aber nur kurzfristig den Säure-Basen-Status. Dabei wird durch vermehrte Dissoziation der Anteil an freier Säure, der die Zelltoxicität trägt, vermindert, ohne daß die Gesamtkonzentration an Ameisensäure im Plasma verändert wird. Die Wirkung von THAM ist zur Hauptsache auf eine intracelluläre Alkalisierung, die von Natriumbicarbonat auf eine Verminderung der Ameisensäurekonzentration in der Zelle zurückzuführen.Der med.-techn. Assistentin Fräulein J.Ahamer danken wir für die wertvolle Mitarbeit.     

Die Diffusionskapazität der Lunge als Maß der Wirkung geringer Reizgaskonzentrationen

Ohne Zusammenfassung     

Modulation of benzo[a]pyrene-induced morphological transformation of Syrian hamster embryo cells by butylated hydroxytoluene and butylated hydroxyanisole

The Syrian hamster embryo cell transformation assay has been used to investigate the effect of two synthetic antioxidants on morphological transformation induced by the initiator benzo[a]pyrene (BP). A two-stage protocol was employed with an initiation phase of 2 days and a subsequent promotion phase of 5 days. When 10 microM butylated hydroxytoluene (BHT) were present in the promotion phase instead of the solvent the transformation frequency at 0.1 micrograms BP/ml increased from 0.27% to 0.55%; at 100 microM of BHT the transformation frequency was 0.77%. Butylated hydroxyanisole (BHA) also enhanced the percentage of transformed colonies from 0.40% (10 microM) to 0.49% (100 microM), respectively. No significant initiating activity was detected for both antioxidants when tested in the initiation phase instead of BP; when the antioxidants were applied simultaneously with BP (1 microgram/ml) during the initiation phase the transformation frequency was decreased from 0.64% to 0.15% (100 microM BHT) and to 0.17% (100 microM BHA), respectively. These results show that the dual action of phenolic antioxidants on chemical carcinogenesis, which depends on the administration schedule, can be imitated in an in vitro test system. In addition to their anti-initiation effect, BHT and BHA, while devoid of intrinsic initiator potency, exert a moderate promotional activity on hamster embryo cell cultures. Their ability to enhance tumorigenesis by various carcinogens in vivo is likely to be at least partially related to such promotion-like effects on cell growth and morphology.     

Lungenkrebs durch nitrose Gase?

Ohne Zusammenfassung     

Zur Frage einer cancerogenen Wirkung inhalierter Stickstoffoxyde

Zusammenfassung Zur Überprüfung der von anderer Seite erörterten Möglichkeit, ob nitrose Gase über die Bildung von Nitrosaminen mit gewebseigenen Aminen Lungenkrebs erzeugen können, werden Mäuse bis zu 1 1/2 Jahren mit 40 ppm Stickstoffdioxyd begast. In den Lungen werden keine Carcinome gefunden. Die Häufigkeit der gutartigen, als Spontantumoren bekannten Lungenadenome nimmt mit der Gesamtdosis an inhaliertem NO₂ ab, sie steigt aber mit der Länge der Pausen zwischen den Begasungen an; parallel dazu geht die Intensität von Proliferaten an den terminalen Bronchiolen. Insgesamt übt die alle 10 Tage vorgenommene Exposition in 40 ppm NO₂ über 48 Std eine Hemmwirkung auf die Ausbildung von Lungenadenomen wie auf die von Fibroadenomen der Haut aus, was möglicherweise auf einen durch den dauernden entzündlichen Reiz auf das Lungenparenchym ausgelösten humoralen Hemmechanismus zurückzuführen ist. Stickstoffdioxyd wirkt demnach selbst in der höchsten, eben noch verträglichen Dosierung an der Maus nicht carcinogen. Auf das Fehlen einer carcinogenen Wirkung nitroser Gase ist auch aus gewerbetoxikologischer Erfahrung heraus zu schließen.

---

Summary The possible formation of nitrosamines by the reaction of nitrous fumes with tissue amines was discussed by others as a cause of lung cancer. To test this hypothesis, mice are exposed to 40 ppm nitrogen dioxide for periods up to 1 1/2 years. No carcinomas are found in the lungs of these animals. Benign adenomas of the lung, known as spontaneous tumours in the mouse, are encountered in rates decreasing with raising total dose of inhaled NO₂. However, the rate increases with the length of intervals between the inhalation periods; in parallel, the intensity of proliferative alterations at the terminal bronchioles increases with the length of intervals. In comparison with controls, there is slight inhibition of the formation of lung adenomas and of spontaneous skin fibroadenomas by intermittent exposure to 40 ppm NO₂, for 48 hours every tenth day; a humoral mechanism of inhibition, triggered by the permanent inflammatory irritation of lung parenchyma, is discussed. Thus, nitrogen dioxide in the highest dose tolerated is not carcinogenic in the mouse. The failure of a carcinogenic effect of nitrous fumes in animals is substantiated by experiences in humans exposed to nitrogen oxides in the workplace.

---

---

Vorläufige Mitteilungen: Naturwissenschaften 50, 503 (1963). — Naunyn-Schmiedebergs Arch. exp. Path. Pharmak. 250, 256 (1964).