The prolonged treatment of castrated and ovariectomized rats with testosterone propionate

found that the activity of testosterone on male sexual organs was greatly increased by esterification. Of the various esters prepared the propionate, as judged by short-duration experiments, proved to be the most effective. It brought about a greater increase in the size of the male sexual organs in castrated rats and also a longer duration of the effect than was obtained with other esters; e.g. after a single injection of 2 mg. of testosterone propionate, dissolved in 2 ml. of sesame oil, or after two injections of 1 mg. in 1 ml. of sesame oil with a 5-day interval, the maximum effect was obtained on about the 11th day after the first injection, the activity lasting at least 2-4 weeks. With testosterone the activity had disappeared by the 11th day, the maximum effect being observed a few days after the injection. Parkes [1936] also confirmed the results quoted above in short-duration experiments on the prostate and seminal vesicles.