Objectives: To study the effects of gonadotropin on the expression of growth differentiation factor-9 (GDF-9) and -9B (GDF-9B) in mouse ovary.
Methods: We chose follicles of mature mice cultured in vitro and mature BALB/c mice as our animal models. (1) In vivo experiment. Twenty mice were divided into two groups (groups A and B) randomly with ten mice in each group. Each mouse was injected with 10 IU pregnant mare's serum gonadotropin in group A and saline of the same volume was given to the other group. Twenty-four hours later we obtained ovarian tissue and immunohistochemistry and in situ hybridization were performed to detect the expression of GDF-9 and GDF-9B. (2) In vitro experiment. Fifty-eight separated follicles were divided into two groups (groups C and D) randomly and cultured in vitro. Thirty-two follicles in group C were cultured in medium with follicular stimulating hormone (FSH) for 72 hours while 26 were cultured without FSH. Immunohistochemistry was performed to detect the expression of GDF-9 in both groups.
Results: We abserved 370 follicles by immunohistochemistry. The weak positive (+ or ++) rate was 22.0% and 46.2% while the strong positive (+++ or ++++) rate was 22.6% and 9.1% in 186 follicles of group A. The weak positive (+ or ++) rate in group B was 42.4% and 42.9% while the strong positive (+++ or ++++) rate was 14.1% and 0.5%. The expression of GDF-9 was higher in group A than that of group B. The weak positive rate, positive rate and strong positive rate in group C was 28.1%, 53.1% and 18.8% while that in group D was 61.5%, 30.8% and 7.7%, respectively. The expression of GDF-9 was higher in group C than that of group D. We observed 362 follicles by in situ hybridization. The weak positive (+ or ++) rate was 31.5% and 46.2% while the strong positive (+++ or ++++) rate was 21.2% and 1.1% in 184 follicles of group A. The weak positive (+ or ++) rate in group B was 39.9% and 41.6% while the strong positive (+++ or ++++) rate was 15.7% and 2.8%. There were no differences in the expression of GDF-9B between groups A and B.
Conclusion: Gonadotropin increases the expression of GDF-9 in vivo while FSH increases GDF-9 in vitro. Gonadotropin has no effects on the expression of GDF-9B.