title: Potent carcinogenicity of 2,7-dinitrofluorene, an environmental pollutant, for the mammary gland of female Sprague-Dawley rats.
abstract: Nitrofluorene compounds are environmental pollutants chiefly from incomplete combustion. This study examined carcinogenicities after one intramammary injection of 2-nitrofluorene (2-NF), 2, 7-dinitrofluorene (2,7-diNF) or dimethyl sulfoxide (DMSO) (solvent control) to 30-day-old and of 2-NF, 9-OH-2-NF, 9-oxo-2-NF, 2,7-diNF, 9-oxo-2,7-diNF, 2,5-dinitrofluorene, 9-oxo-2,4,7-trinitrofluorene, N-OH-2-acetylaminofluorene (N-OH-2-AAF) (carcinogen control) or DMSO to 50-day-old female Sprague-Dawley rats. In 30- and 50-day-old rats 6 and 8 glands/rat, respectively, were injected with 2.04 micromol of compound in 50 microliter/gland of DMSO. Whereas all compounds including DMSO yielded combined malignant and benign mammary tumor incidences of 33-87% by week 82 after injection, 2,7-diNF produced 100 and 93% incidences significantly (P < 0.001) sooner than did DMSO, i.e. by weeks 23-49 and 18-48 after treatment of 30- and 50-day-old rats, respectively. Rats treated with 2,7-diNF and 9-oxo-2,7-diNF had significantly (P < 0.0001) and marginally (P = 0. 0536) more mammary tumors, respectively, than DMSO-treated rats. In 2,7-diNF-treated rats, the ratio of malignant to benign mammary tumors was 5.4, whereas in all other groups it was <0.5. N-OH-2-AAF, a potent tumorigen when applied to the mammary gland as a solid or in suspension, did not yield the expected tumorigenicity here. The contrasting tumorigenic potencies of 2,7-diNF and N-OH-2-AAF may have been prompted by differences in their solubilities in DMSO. Thus, the poorly soluble 2,7-diNF was slowly absorbed from the injection sites since residues (up to 0.9% of the dose injected) were recovered even after 45 weeks. The data indicate prolonged exposure of the mammary gland to 2,7-diNF and suggest that contamination of the environment with 2,7-diNF, even at low levels, poses substantial carcinogenic risk.
authors.affiliation: Veterans Affairs Medical Center, Minneapolis, MN 55417, USA. malej001@maroon.tc.umn.edu
authors.forename: D
authors.initials: D
authors.lastname: Malejka-Giganti
authors.forename: G A
authors.initials: GA
authors.lastname: Niehans
authors.forename: M A
authors.initials: MA
authors.lastname: Reichert
authors.forename: K K
authors.initials: KK
authors.lastname: Bennett
authors.forename: R L
authors.initials: RL
authors.lastname: Bliss
mesh_terms: D000818:Animals; D015197:Carcinogenicity Tests; D002274:Carcinogens, Environmental / Q000633:toxicity*; D002851:Chromatography, High Pressure Liquid; D005260:Female; D005449:Fluorenes / Q000633:toxicity*; D008325:Mammary Neoplasms, Experimental / Q000139:chemically induced*; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D002274:Carcinogens, Environmental; D005449:Fluorenes; C085049:2,7-dinitrofluorene