Synergy of abdominal pressure and androgens in testicular descent.

The potential synergistic activity between intra-abdominal pressure and androgens in facilitating testicular descent was investigated in the rat. In the rat, the testis normally descends on or about the 21st day of age. If one testis is excised at 14 days of age and replaced by a silicone prosthesis, the silicone prosthesis will descend into the scrotum in approximately 11/20 (55%) of the animals by 28 days of age. If both testes are excised at 14 days of age and a solitary silicone prosthesis is then placed into the abdominal cavity, the prosthesis will descend into the scrotum in approximately 4/18 (22%) of the animals. However, if both testes are excised at 14 days of age and a silicone prosthesis is placed into the abdominal cavity but the animals are treated daily from Day 14 to Day 27 of age with 2 mg of dihydrotestosterone, the prosthesis will at 28 days of age descend into the scrotum in 10/16 (63%) of the animals treated. These data suggest that: 1) androgens do not appear to be solely responsible for testicular descent in the rat; 2) another mechanism such as intra-abdominal pressure may be operative in facilitating testicular descent in this animal species; and 3) there may be some synergism between androgens and intra-abdominal pressure in promoting testicular descent.