Binding characteristics of inhibin in rat ventral prostate

Homogeneous preparation of human seminal plasma inhibin (molecular weight 13,500) was iodinated with 125I to a specific activity of about 40-45 microCi/micrograms and tested for binding to a rat prostate crude membrane preparation. The binding of inhibin was a saturable process as well as time and temperature dependent. This binding was displaceable in a dose-dependent manner by unlabelled inhibin. Other hormones such as LH, FSH, Prl, and TSH from rat or human origin did not influence the binding of labelled inhibin to rat prostate membrane. Of various age groups of rats studied, the maximum binding was observed in 75-day-old rats. The radiolabelled inhibin also showed specific binding to rat pituitary. The preliminary studies regarding involvement of steroids in the control of inhibin receptors in prostate and pituitary indicated that testosterone activates the inhibin receptors at the prostatic level whereas estradiol did not have any effect. However, estradiol increases the pituitary receptors for inhibin as compared to testosterone.