The inductive effects of progestogens on aromatase activity in stromal cells of human uterine endometrium

Aromatase activity for androstenedione was measured in stromal cells of human uterine endometrium throughout the menstrual cycle. The effect of progestogen on aromatase activity was also examined in the endometrial stromal cells. Aromatase activity tended to be high in the proliferative cells compared to the secretory cells. Moreover, its enzyme activity was enhanced at the concentration of 0.1 or 1.0 microM of medroxyprogesterone acetate (MPA) and norethindrone (ENT) in all phases of menstrual cycle. MPA stimulated aromatase activity in the stromal cells more strongly than did ENT. These results may suggest that although aromatase in uterine endometrium is not regarded to be so much influenced by endogenous progesterone during menstruation, the increase of aromatase activity by progestogen added lead to the more differentiated endometrium.