Reduction of prostatic binding protein-messenger ribonucleic acid sequences in rat prostate by castration

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Abstract
MRNA coding for the 3 subunits of prostatic binding protein was isolated from polysomal RNA of rat ventral prostate by oligo(dT)-cellulose affinity chromatography and purified by repeated sedimentations through sucrose gradients under denaturing conditions. The purified mRNA migrated as a 9S peak in sucrose gradient centrifugation and hybridized with its c[complementary]DNA within 2 log R0t units. In a cell-free reticulocyte lysate system, the mRNA directed the synthesis of 3 polypeptides of 12,000, 9000 and 8000 daltons. These translation products were identified as the subunits of prostatic binding protein by immunoreaction with antibodies to this protein. Quantitation of prostatic binding protein-mRNA sequences in normal and castrated rats by hybridization with the cDNA [complementary DNA] probe showed that 3-day castration reduced the prostatic binding protein-mRNA sequences to < 2% of the normal level. Similar hybridization was performed by using the cDNA to determine the level of prostatic binding protein coding sequences in polysomal poly(A) RNA following castration. The results showed a 1st-order rate constant of 3.92 x 10-2 h-1 for reduction of prostatic binding protein-mRNA sequences in polysomes. The period of castration required to reduce the level of these sequences to 50% of the normal level was calculated to be 17.6 h.