Studies on Radiation-Induced Mammary Gland Neoplasia in the Rat: II. The Response of Castrate and Intact Male Rats to 400 r of Total-Body Irradiation

Abstract

Male Sprague-Dawley rats, both castrates and intact, had a 50% incidence of breast neoplasms 16 months after exposure to 400 r of 250-kvp total-body X-radiation delivered as a single dose on the fortieth day of age. Nonexposed intact or castrate Sprague-Dawley male rats of the same age had an incidence of 0 or 6%, respectively. Thus total-body irradiation may hasten onset of neoplasms and also induce a higher incidence of neoplasms of the breast of the male Sprague-Dawley rat. Although both male and female rats of the Sprague-Dawley strain respond to total-body irradiation by the formation of neoplasia of the breast, gonadal hormones can influence the frequency, latent period, and histological appearance of the induced neoplasms.