Aminopeptidases of the rat prostatic complex and seminal vesicles: secretion and effect of castration

Aminopeptidases hydrolysing L-leucine-beta-naphthylamine (LeuNA), L-alanine-beta-naphthylamide (AlaNA) and L-arginine-beta-naphthylamide (ArgNA) were studied in tissue homogenates of various parts of the rat prostatic complex and seminal vesicles after castration as well as in their 'cellular' and 'secretory' compartments. The 'secretory' fluids were also fractionated by chromatofocusing to reveal the enzymes possibly secreted by the glands. After castration the ventral prostate showed a temporary increase of LeuNA and a continuous rise of AlaNA hydrolysis, while ArgNA hydrolysis remained unaltered. Its 'secretory' fluid contained high hydrolysis rates of the substrates and chromatofocusing revealed two activity peaks with pI values of 6.2 and 5.4. In the lateral prostate no activity changes were recorded after castration. The 'secretory' fluid contained low enzyme activities and the fractionation showed one enzyme activity with pI 5.4. The posterior prostate, coagulating glands and seminal vesicles showed high hydrolysis rates of ArgNA with a rapid decline after castration. The 'secretory' fluid of posterior prostate contained rather low activity levels and in chromatofocusing two activity peaks with pI values of 6.2 and 5.4 were found. The 'secretory' fluid of coagulating gland contained a strong hydrolysis of ArgNA and chromatofocusing gave two activities with pI values of 5.4 and 5.1. The latter seemed to hydrolyse only ArgNA. The viscous secretion of the seminal vesicles contained very low aminopeptidase activities and chromatofocusing also showed a poor result. It is concluded that the various parts of the rat prostatic complex differ in their aminopeptidase composition. Only part of these enzymes appears to be secretory and controlled by testosterone. The major contribution to the seminal plasma aminopeptidase activity seems to derive from the ventral prostate and the coagulating gland.