The concentration of zinc in the prostate gland was studied in dogs with prostatic fistulas by injecting the radioactive isotope Zn65 intravenously. The ability of the canine prostate to concentrate and secrete zinc was demonstrated. The amount of zinc stored in the gland decreased after orchiectomy and increased greatly after administration of testosterone. It was also found possible to study the concentration of zinc in the human prostate by the preoperative intravenous injecttion of 108 to 150μc of Zn65 and the subsequent examination of normal and abnormal prostatic tissue removed in such operations as radical cystectomy. The normal prostate contained more Zn65 than did any other normal tissues examined, and neoplastic prostatic tissue generally contained less than normal prostatic tissue or tissue manifesting benign hyperplasia.
Prout GR, Sierp M, Whitmore WF. RADIOACTIVE ZINC IN THE PROSTATESOME FACTORS INFLUENCING CONCENTRATIONS IN DOGS AND MEN. JAMA. 1959;169(15):1703-1710. doi:10.1001/jama.1959.03000320005002