Presence of a low capacity androgen receptor in the gubernaculum of the pig fetus.

The aim of our study was to investigate the theory that the gubernaculum is an androgen-responsive structure responsible for fetal testicular descent. Using 3H-methyltrienolone (3H-R1881) as ligand, we performed a seven-point Scatchard analysis of androgen receptor binding in the gubernaculum, prostate, urethra and striated muscle tissue obtained from pig fetuses between 60 and 109 days of gestation. The gubernaculum demonstrated androgen receptor binding with an affinity and capacity significantly lower than that of fetal pig prostate and urethra, but not significantly different from that of striated muscle taken from both male and female fetuses. A marked increase in the size and mass of the gubernaculum of male (but not female) fetuses is known to accompany testicular descent. If the dramatic increase in the mass of the gubernaculum observed in male (but not female) fetuses were the result of androgen stimulation, it may be expected that the striated muscle mass (and therefore total body mass) of male fetuses should be greater than that of female fetuses, since the androgen receptor affinity and capacity of the gubernaculum is similar to that of striated muscle. However, we found no significant difference in total body mass between male and female pig fetuses at the same period of gestation. These findings raise doubt concerning the theory that growth of the gubernaculum during descent is the result of androgen stimulation.