title: On the presence of prostatic secretion protein in rat seminal fluid.
abstract: The copulating plug collected from the tip of the penis from rats immediately after decapitation contains a protein very similar and probably identical to PSP (prostatic secretion protein); this protein has earlier been purified from rat prostatic cytosol and characterized. The protein present in the copulating plug interacts with [3H]estramustine and binds to the antibody raised against rat PSP. The concentration of the protein in the copulating plug is 400 ng/mg of total protein, when measured using the radioimmunoassay technique developed earlier for measurement of PSP in rat prostate. The [3H]estramustine-protein complex formed in a preparation of the copulating plug has an apparent molecular weight of about 50,000 and a sedimentation coefficient of about 3S when analyzed using sucrose density gradient centrifugation. The complex was retained on Concanavalin-A Sepharose indicating that the protein is a glycoprotein. Binding of the complex was also observed on hydroxylapatite and DEAE-Sephadex columns, from which it was eluted at 0.18 M KCl. Light microscope autoradiograms of rat sperms incubated with 125I-labeled PSP indicated that PSP is bound to all parts of the sperms. A macromolecule interacting with the PSP-antibodies is also present in human seminal fluid but at a concentration considerably lower than in rat seminal fluid. The present study shows that a macromolecule probably identical to prostatic secretion protein is present in the copulating plug from the rat. The biological role of this protein in normal male fertility is discussed.
mesh_terms: D000818:Animals; D002845:Chromatography; D004961:Estramustine / Q000378:metabolism; D007457:Iodine Radioisotopes; D008297:Male; D011467:Prostate / Q000032:analysis / Q000378:metabolism*; D011506:Proteins / Q000032:analysis*; D051381:Rats; D011919:Rats, Inbred Strains; D012661:Semen / Q000032:analysis* / Q000378:metabolism; D013094:Spermatozoa / Q000032:analysis; D014316:Tritium
chemical_list: D007457:Iodine Radioisotopes; D011506:Proteins; D014316:Tritium; D004961:Estramustine