EFFECT OF OVARIECTOMY ON HORMONE RECEPTORS AND GROWTH OF N-NITROSOMETHYLUREA-INDUCED MAMMARY-TUMORS IN THE RAT

Abstract

Estrogen receptor(s) (ER), progesterone receptor(s) (PGR), androgen receptor(s) (ANR) and prolactin receptor(s) (PRLR) were measured in N-nitrosomethylurea-induced mammary tumors in intact female Sprague-Dawley rats, and in rats 9 days after ovariectomy. Following ovariectomy, 12 of 15 tumors regressed to 47.7 .+-. 5.5% of the original size (hormone-dependent tumors), while the remaining 3 had arrest of growth reaching 88.8 .+-. 7.3% of their original sizes. The majority of N-nitrosomethylurea-induced rat mammary tumors are hormone dependent. ER, PGR and PRLR were abundantly present in the majority of these tumors, while ANR was present in only 4 of 13 tumors. The levels of ER and PGR were significantly lower following ovariectomy, while PRLR was not significantly changed.