Assay of 1-nitropropane, 2-nitropropane, 1-azoxypropane and 2-azoxypropane for carcinogenicity by gavage in Sprague--Dawley rats

1-Nitropropane (1-NP), 2-nitropropane (2-NP), 1-azoxypropane(1-AP) and 2-azoxypropane (2-AP), were assayed for carcinogenicityby gavage in male Sprague—Dawley rats. 2-NP was givenat 1 mmol/kg three times per week for 16 weeks. 1-NP (1 mmol/kg),1-AP (0.1 mmol/kg), 2-AP (0.1 mmol/kg) or Emulphor EL-620 vehiclewas given three times per week for 16 weeks, and then once perweek for 10 weeks. In the 2-NP treated group both benign andmalignant liver tumors occurred in 100% of the animals. No treatmentrelated tumors occurred in rats receiving 1-NP. In rats treatedwith 1-AP, a high incidence of skin tumors (100%), mostly keratoacanthomas,and of tumors of the nasal cavity (59%) was observed. Rats whichwere given 2-AP also showed an increased incidence of skin keratoacanthomas(21%), but not of other tumors. These findings (i) confirm,using the oral route of administration, the results of inhalationstudies by others indicating the potent hepatocarcinogenicityof 2-NP, (ii) establish a practical model in which the mechanismof 2-NP carcinogenicity can now be more readily studied, and(iii) demonstrate that 1-AP, and probably 2-AP, like other aliphaticazoxy compounds thus far examined, are carcinogenic in rats.