Figure 4.

Inhibition of estradiol-stimulated gene expression by progestins in mammary gland and uterus. Ovariectomized C57BL/6 mice were treated over 3 wk with vehicle, 100 ng estradiol, or different doses of MPA or drospirenone plus 100 ng estradiol. In the mammary gland, estradiol-activated INDO expression was inhibited by increasing the dose of progestin (A and B), whereas in the uterus, estradiol-induced LTF expression (C and D) was down-regulated by both progestins. ID₅₀ values were calculated for the inhibition of estradiol-induced gene expression by MPA (A and C) and drospirenone (B and D) in the mammary gland (A and B) and uterus (C and D).