Activity Rhythm and Breast Cancer in Pituitary-Isografted C and D8 Mice; Effect of Hypothalamus.

Abstract

Multiple pituitary isografts induce or enhance carcinogenesis in virgin female mice of the D8 and C stocks, respectively. Number of implants and mammary tumor agent are significant but not critical variables in this type of carcinogenesis. Insertion of the hypothalamus at the time of pituitary implantation delays mammary carcinogenesis by unknown mechanisms. A light-dark synchronized activity rhythm persists in pituitary-isografted C mice, suggesting persistence of adrenal cycle in these mice with a significantly altered estrous cycle.