[Effect of vitamin A and hormones on the hormonal sensitivity of DMBA-induced mammary tumors in rats].

The treatment of rats with DMBA-induced mammary tumours with vitamin A and hormones in the cyclic regime increases the lifetime of animals, decreases both the tumour growth rate and increases the degree of their differentiation. The treatment with vitamin A alone and in combination with hormones lowers the level of estradiol and progesterone receptors in the rat mammary tumours. The high frequency of receptor-positive tumours and high level of estradiol and progesterone receptors in them were observed under the influence of hormones alone in the cyclic regime.

[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.