Abstract
After administration of testosterone to immature rats which had ovulated after treatment with PMSG and hCG, a significant increase in ovarian content of estradiol–17β was observed. Together with our previous result on the immediate decrease in ovarian 17α-hydroxylase and C-17-C-20 lyase after PMSG and hCG treatment, it is concluded that the drastic decrease in serum estradiol-173 after ovulation is caused by a shortage of supply of aromatizable androgen(s) to the ovarian aromatase, due to diminished activities of the above two enzymes.