[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.