Proteins of the rat prostate. III. Effect of testosterone on protein synthesis by the ventral prostate of castrated rats.

Protein synthetic activities in the ventral prostate were assessed by two-dimensional electrophoresis in either four-day or seven-day castrated rats at different intervals following subcutaneous implantation of testosterone-filled silastic tubings for a period of up to four days. Prostatic tissues were cut into one to two mm. pieces and incubated in tissue culture medium containing S35-methionine (100 microCi/ml.) at 37C under 95% oxygen and 5% carbon dioxide for four hours. The incubated tissues were subjected to two-dimensional electrophoresis and radiofluorography. Analysis of protein spots detected in the fluorograms by computer-assisted densitometry revealed temporal changes in the synthesis of individual proteins by the ventral prostate of castrated rats following androgen treatment. Changes in two groups of proteins were evaluated: castration-induced proteins and androgen-dependent proteins. The level of synthesis of three castration-induced proteins (spots G, H, and I) declined rapidly upon testosterone treatment and reached a non-detectable level for spots G and H and a low level of synthesis for spot I by three days following androgen treatment. Synthesis of androgen-dependent proteins (spots D, E, and F) was activated by testosterone treatment. However, the time interval required to activate the synthesis of these proteins is different. Synthesis of protein spot D (prostatic binding protein) was detected as soon as half hour after the treatment. Synthesis of spots E and F, on the other hand, was not activated until 24 and 48 hours after the treatment, respectively. These changes in patterns of protein synthesis represent the characteristics of cellular responses to testosterone stimulation by the regressed prostate.