[Estradiol and progesterone receptors in DMBA-induced mammary neoplasms in rats under cyclic hormonal exposures]

Hormones in physiological doses and under cyclic regime were injected to rats with DMBA-induced mammary tumours. It is demonstrated that 17-alpha-hydroxyprogesterone capronate (HPC) alone administered once every 6 days reduces estradiol receptor (ER) and progesterone receptor (PR) levels and the frequency of R+ tumours. Under the influence of a successive use of HPC and testosterone (TS) the level of PR and the frequency of PR+ tumours were reduced. A high level of ER and PR and a high frequency of R+ tumours were observed after a successive administration of insulin, prednisolone, HPC and TS. All the variants of hormonal influences resulted in an increased life duration of animals, a reduced growth rate, and an increased degree of mammary tumour differentiation.