Testicular blood flow, vascular permeability, and testosterone production after stimulation of unilaterally cryptorchid adult rats with human chorionic gonadotropin.

Testicular blood flow, testosterone production, and the formation of testicular interstitial fluid (IF) were studied in unilaterally cryptorchid rats, basally, 8 h and 24 h after treatment with 200 IU human CG (hCG). Testicular blood flow was lower in the abdominal testis in both control rats and hCG-treated rats than in the scrotal testis within the same treatment group. The scrotal testicular blood flow increased significantly 24 h after hCG treatment, but not after 8 h. In the abdominal testis, there was a significant increase of blood flow 8 h after hCG, but not 24 h after. The formation of IF was subnormal in the abdominal testes of control rats, but this was corrected in hCG-treated rats, where there was a significant increase of IF in both abdominal and scrotal testes. The total endothelial surface of small blood vessels was decreased in abdominal testes. Testosterone concentration in the spermatic vein was significantly lower on the abdominal side than on the scrotal side in both control and hCG-treated rats. The concentration of testosterone was lower in IF on the abdominal side in control rats, but after hCG the testosterone concentration was similar in both scrotal and abdominal testes, indicating a trapping of testosterone in the abdominal testis. The outflow of testosterone in the spermatic vein was significantly increased at both 8 and 24 h after hCG from both the scrotal and abdominal testes, although it was always smaller from the abdominal testis. The lower secretion of testosterone from the abdominal testis after hCG was mainly due to reduced blood flow and not to any disability of the Leydig cells of abdominal testes to produce testosterone.