Prostate Specific Antigen (PSA)
Prostate specific antigen (PSA) is a glycoprotein produced by prostatic acinar cells and ductal epithelium, which is normally secreted into the prostatic ductal system, where it is present in high concentrations. PSA possesses kallikrein-like serine protease activity, which dissolves seminal gel formed immediately after ejaculation. PSA is present in seminal fluid, prostate tissue, peripheral blood, and urine. Normally, very little PSA enters the general circulation. Only after a significant derangement of prostate architecture, does PSA escape from the ductal system and enter the general circulation via the lymphatics and capillaries.