Objective To investigate the contraceptive mechanism of combination regimen of low-dose gossypol acetic acid (GA) with steroid hormones [desogestre/ethinylestradiol/testosterone undecanote(DSG/EE/TU)]. Methods Adult male rats were randomly divided into four groups. Group GH: rats were fed orally with gossypol acetic acid (GA, 12.5mg/kg) and desogestrel (DSG, 0.125mg/kg)/ ethinylestradiol (EE, 0.025mg/kg)/testosterone undecanoate (TU, 100mg/kg per day, qd×4 weeks or 10 weeks); group G: a single dose of GA (12.5mg/kg per day, qd×4 weeks or 10 weeks); group H: the same dosage of DSG/EE/TU as in group GH; group C: rats were treated with vehicle (1% methyl cellulose) as the control. Expression of protein kinase C alpha (PKC-α) and cyclin D1 in rat testes were tested mainly by immunohistochemistry (IHC) and Western blotting. Results IHC results showed that protein PKC-α was expressed mainly in interstitial tissue of testis among seminiferous tubule. The expression of PKC-α in groups H and GH at week 10 was decreased greatly compared with that in group C. The protein cyclin D1 was expressed mainly in residual body of seminiferous tubule cavosurface and interstitial tissue among seminiferous tubule of testis. Western blotting results showed that the expression of PKC-α in groups H and GH at week 10 was decreased significantly compared with that in group C (P<0.05). The expression of cyclin D1 in groups G, H or GH at week 10 rose significantly compared with that in group C (P<0.05).Conclusion The administration of low-dose gossypol acetic acid with steroid hormones for 10 weeks can decrease the expression of PKC-α greatly. Objective To investigate the contraceptive mechanism of combination regimen of low-dose gossypol acetic acid (GA) with steroid hormones [desogestre / ethinylestradiol / testosterone undecanote (DSG / EE / TU)]. GH: rats were fed orally with gossypol acetic acid (GA, 12.5 mg / kg) and desogestrel (DSG, 0.125 mg / kg) / ethinylestradiol group G: a single dose of GA (12.5 mg / kg per day, qd × 4 weeks or 10 weeks); group H: the same dosage of DSG / EE / TU as in group GH ; Group C: rats were treated with vehicle (1% methyl cellulose) as the control. Expression of protein kinase C alpha (PKC-α) and cyclin D1 in rat testes were tested mainly by immunohistochemistry (IHC) and Western blotting. Results IHC results showed that protein PKC-α was expressed primarily in interstitial tissue of testis among seminiferous tubule. The expression of PKC-α in groups H a nd GH at week 10 was decreased greatly compared with that in group C. The protein cyclin D1 was expressed mainly in residual body of seminiferous tubule cavosurface and interstitial tissue among seminiferous tubule of testis. Western blotting results showed that the expression of PKC-α in groups H and GH at week 10 was significantly decreased compared to that in group C (P <0.05). The expression of cyclin D1 in groups G, H or GH at week 10 rose significantly compared with that in group C (P <0.05) .Conclusion The administration of low-dose gossypol acetic acid with steroid hormones for 10 weeks can decrease the expression of PKC-alpha greatly.