Activities of cathepsin D in rat prostate during castration induced involution.

The possibility that an intracellular proteolytic process is activated during castration induced prostatic regression warrants consideration and investigation. We investigated the activities of cathepsin D, a lysosomal proteolytic enzyme, in the prostate of rats at different intervals following castration. The enzyme activity was noted to increase during the period of rapid prostatic involution. Administration of exogenous testosterone in varying doses to castrated rats prevented or retarded prostatic weight loss as well as the increase in cathepsin D activity in a dose related manner. Administration of actinomycin D to castrated rats also retarded ventral prostate regression and decreased cathepsin D activity. These observations suggest that cathepsin D is actively synthesized in the regressing prostate and that the enzyme may play an important role in castration induced prostatic regression.