Increased incidence of mammary tumors in rats after direct or transplacental exposure to 3-hydroxyxanthine.

ABSTRACT

Rats were exposed directly or transplacentally to the carcinogenic purine N-oxide 3-hydroxyxanthine (3-OH-X). Among female noninbred Wistar rats given 3-OH-X sc, beginning at suckling or weaning ages, there was a significantly greater proportion of mammary tumor bearers and a higher mean number of mammary tumors per rat than among controls. This effect was seen even at low doses producing no other neoplasms such as hepatic carcinomas or fibrosarcomas and fibromas at the site of injection. Noninbred Sprague-Dawley rats, treated transplacentally with 3-OH-X by ip injection into pregnant females, also also had a significantly greater incidence of mammary tumors than did controls.