Effect of testicular hormones on synthesis of soluble proteins by dog prostate slices

Abstract

We have submitted adult mongrel dogs to various endocrine manipulations. Prostate slices from these animals were then incubated in vitro in the presence of [3H]leucine or [35S]methionine. We have analyzed the cytosolic proteins by polyacrylamide gel electrophoresis. In intact adult uncastrated dogs, the radioactive amino acids were incorporated into three major bands having respective molecular weights (MW) of 32 000,16 000, and 15 000 in one-dimensional gels in presence of sodium dodecyl sulfate and mercaptoethanol. Two-dimensional electrophoresis revealed heterogeneity of each of these bands, both in isoelectric focussing (IEF) or nonequilibrium pH gel electrophoresis (NEpHGE) conditions. The 32 000 MW proteins showed five to six major radioactive spots and the 15 000 – 16 000 MW proteins showed six to seven spots by IEF. However, the highest incorporation of radioactivity occurred in a 16 000 MW protein seen only in NEpHGE. The lower MW proteins corresponded to some of the major proteins of dog seminal plasma as observed by immunoprecipitation of prostate proteins with antibodies against whole seminal plasma. By contrast, the 32 000 MW proteins were minor proteins of prostate cytosol and seminal plasma by Coomassie blue staining. Castration for 2 weeks completely abolished the synthesis of all these proteins. When castrated animals were treated with 5α-androstane-3α-17β-diol (10 mg/day for 2 weeks), the pattern of protein synthesis returned to the one observed in intact uncastrated animals. These observations show that testicular androgens control the synthesis of dog prostate major secretory proteins.