Abstract： Objective To investigate the effect of anti-Mlllerian hormone (AMH) on hormone secretion and P450 aromatase mRNA expression from cultured human luteinized granulosa cells. Methods Human luteinized granulose cells were derived from 10 patients treated by in vitro fertilization-embryo transplantation (IVF-ET) in the Second Affiliated Hospital of Sun Yat-sen University from June to December 2006. Granulose cells were divided into group A, B, C, D, E depending on different concentration of AMH,testosterone group and blank group. 1×10-7moL/L testosterone and 1,5,10,20,50 μg/L AMH were added into the culture medium of group A,B,C,D and E. 1×10-7mol/L testosterone was added into the culture medium of testosterone group while no other ingredient was added into the medium of blank group. Estrogen levels in supernates were measured at 24,48,72 hours after cell incubation. RT-PCR was performed to detect the P450 aromatase mRNA expression in group B, C, D, E and testosterone group at 72 hours after cell incubation. Results (1) Estrogen levels in supernates of granulose cell culture at 24,48,72 hours were (8.529±0.381)×104, (10.977±0.436)×104, (13.309±0.506)×104 pmol/L in group A, (7.027±0.276)×104, (9.167±0.300)×104, (10.794±0.555)×104 pmol/L in group B, (6.039±0.226)×104,(7.585±0.548)×104, (8.797±0.518)×104 pmol/L in group C, (5.118±0.460)×104, (5.716±0.496)×104, (6.205±0.667)×104 pmol/L in group D, (4.932±0.148)×104, (5.323±0.184)×104,(5.629±0.212)×104 pmol/L in group E. When compared with blank group [(0.001±0.001)×104,(0.006±0.003)×104, (0.029±0.011)×104 pmol/L], the statistical differences were observed in group A,B,C,D,E(P<0.01) ; when compared with testosterone group [ (8.418±0.569)×104, (10.841±0.689)×104, (13.301±0.637)×104 pmol/L], the statistical differences were observed in group B,C,D and E(P<0.01) ; statistical differences were also observed in group C, D and E when compared with group B, and also group D and E when compared with group C(P<0.01). No significant difference was observed between group D and E (P>0.05). In group A, B, C, D, E and testosterone group, the estrogen levels at 24 hours after cell culture were significantly lower than those at 48 and 72 hours (P<0.01) ; statistical difference was observed between estrogen levels at 48 and 72 hours(P<0.01). No significant difference was observed among 24,48 and 72 hours in blank group (P>0.05). (2) Relative ratios of intensity of P450 aromatase/β-actin at72 hours of cell culture in group B,C,D and E were 0.6148±0.0046, 0.5156±0.0012, 0.4698±0.0027 and 0.4282±0.0017, respectively, which were statistically lower than that in testosterone group (0.8224±0.0021, P<0.01) ;statistical differences were also observed in group C, D and E when compared with group B, and also group D and E when compared with group C(P<0.01). No significant difference was observed between group D and E (P>0.05). Conclusion It is suggested that AMH might affect estrogen synthesis by inhibiting P450 aromatose activity so that lead to hyperandrogenism microenvironment in local ovary.