Testosterone is prehormone of estradiol and most of it will converted to estradiol in ovary. The production of testosterone was regulated directly by luteinizing hormone and 17α-hydroxylase which is the rate-limiting enzyme in the production of testosterone.So 17α-hydroxylase and LHR gene expression reflec the response to LH of ovarian cells. In order to investigate the ovarian functions, the 17α-hydroxylase and LHR gene expression was detected simultaneously by using ribonuclease protection assay (RPA) and the sensitivity of RPA is about 8 times more compared with Northern blot.