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

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Abstract
Adult mongrel dogs were submitted to various endocrine manipulations. Prostate slices from these animals were then incubated in vitro in the presence of [3H]leucine or [35H]methionine. The cytosolic proteins were analyzed by polyacrylamide gel electrophoresis. In intact adult uncastrated dogs, the radioactive amino acids were incorporated into 3 major bands having respective MW of 32,000, 16,000 and 15,000 in 1-dimensional gels in the 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 5-6 major radioactive spots and the 15,000-16,000 MW proteins showed 6-7 spots by IEF. 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 wk completely abolished the synthesis of all these proteins. When castrated animals were treated with 5.alpha.-androstane-3.alpha.,17.beta.-diol (10 mg/day for 2 wk), the pattern of protein synthesis returned to the one observed in intact uncastrated animals. Testicular androgens control the synthesis of dog prostate major secretory proteins.