title: Inhibition of benz[a]pyrene-induced mammary carcinogenesis by retinyl acetate.
abstract: The administration of a 250-ppm retinyl acetate dietary supplement for various periods relative to intragastric administration of 50 mg benzo[a]pyrene (BP) significantly inhibited the induction of mammary cancers in virgin female inbred LEW/Mai rats. with day of BP administration taken as time 0, groups receiving the retinoid from weeks -2 to +1, +1 to +90, +20 to +90, and -2 to +90 showed a significant reduction in tumor response as compared to controls. The inhibition of carcinogenesis achieved by a +1 to +20 administration schedule was temporary; the tumor yield was suppressed initially but returned to control levels by week 60. Autoradiographic analysis of mammary glands from 50-day-old rats indicated that a 2-week exposure to supplemental retinyl acetate significantly reduced the mammary gland parenchymal cell labeling index in ductal, alveolar, and terminal end bud structures. Beginning the retinyl acetate supplement 1 week after the administration of BP significantly reduced the number of terminal ductal hyperplasias. The inhibition of carcinogenesis achieved by a short period of retinyl acetate administration before and during the period of carcinogen availability as well as the inhibition achieved by long-term postcarcinogen retinoid exposure may involve an antiproliferative effect on the rat mammary gland.
mesh_terms: D000818:Animals; D001580:Benzopyrenes / Q000008:administration & dosage / Q000037:antagonists & inhibitors*; D001835:Body Weight / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects; D004032:Diet; D004224:Diterpenes; D005260:Female; D006965:Hyperplasia; D007441:Intubation, Gastrointestinal; D008321:Mammary Glands, Animal / Q000473:pathology; D008325:Mammary Neoplasms, Experimental / Q000139:chemically induced* / Q000473:pathology; D011230:Precancerous Conditions / Q000139:chemically induced; D051381:Rats; D011917:Rats, Inbred Lew; D000084562:Retinyl Esters; D014801:Vitamin A / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000494:pharmacology
chemical_list: D001580:Benzopyrenes; D004224:Diterpenes; D000084562:Retinyl Esters; D014801:Vitamin A; C009166:retinol acetate