Increased concentration of prostatic inhibin following orchidectomy in rat

Inhibin, a predominant secretory protein of prostate has been shown earlier to increase in proliferative prostatic diseases. Since the prostate gland is under the profound influence of androgens, it's withdrawal by orchidectomy is many a time included in the therapy to prostate cancer. Hence it was interesting to study the reflection of long term orchidectomy on prostatic inhibin. With this aim two groups of bilaterally orchidectomised male Sprague-Dawley rats were sacrificed 15 days and 30 days after castration respectively. Another group of rats was administered with testosterone enanthate after 30 days of castration. As protein concentration and weight showed a significant decrease after orchidectomy, inhibin concentrations (estimated by RIA) were expressed per gland. The inhibin concentration was increased to a 5-6 fold higher value after 15 days of castration. While a remarkable 10-15 fold elevation of inhibin concentration was observed in 30 day castrated prostates. Concurrently the circulating inhibin levels were also found to be heightened. All these effects of orchidectomy were almost reversed on androgen administration. Thus in contrast to the decrease in the weight and concentration of other prostatic proteins after orchidectomy, the increase in inhibin appears to be striking.