title: The influence of retinyl acetate on the postinitiation phase of preneoplastic lung nodules in rats.
abstract: The effects of retinyl acetate (RA) on the development of carcinogen-induced metaplastic lung nodules were investigated. Four mg of 3-methylcholanthrene were administered intratracheally to F344 rats maintained on a vitamin A-free diet and receiving 31.4 nmoles of RA per week by intragastric intubation. At 3, 5, and 10 weeks after intratracheal instillation of 3-methylcholanthrene, one group of 24 rats each was started on a weekly dose of 31,400 nmoles of RA; a control group was continued on the low-RA dose. Fifty-two weeks after 3-methylcholanthrene injection, the incidence of metaplastic lung nodules was found to be 3% in the combined high-RA-dose groups as compared with 42% in the low-RA-dose group. It is therefore concluded that RA has a significant effects on the postinitiation phase of preneoplastic lung nodules in rats.
mesh_terms: D000818:Animals; D001361:Avitaminosis; D004305:Dose-Response Relationship, Drug; D005260:Female; D008748:Methylcholanthrene; D009374:Neoplasms, Experimental / Q000139:chemically induced; D011230:Precancerous Conditions / Q000139:chemically induced*; D051381:Rats; D011916:Rats, Inbred F344; D014801:Vitamin A / Q000031:analogs & derivatives* / Q000494:pharmacology
chemical_list: D014801:Vitamin A; D008748:Methylcholanthrene