PROSTATE-SPECIFIC ANTIGEN IS METABOLIZED IN THE LIVER

Purpose: The site of metabolism of prostate specific antigen (PSA) was determined. Materials and Methods: In a prospective study, during cli nically indicated left and right heart catheterizations for various ca rdiac diseases in 12 men (mean age 62.5 +/- 8.3 years, standard deviat ion), selective blood samples were obtained from the infra-renal, infr a-hepatic and suprahepatic inferior vena cava, renal vein, superior ve na cava, pulmonary artery and femoral artery. Mean PSA concentration w as calculated for all vascular sites. Using a paired Student t test, t he mean difference between the afferent and efferent PSA concentration s across the renal, hepatic, pulmonary and pelvic circulation was calc ulated.Results: The hepatic gradient between the infra-hepatic and sup rahepatic inferior vena cava showed the greatest decrease (0.11 +/- 0. 16 ng/ml. or 8.3%) in PSA concentration and was statistically signific ant (p = 0.04). A smaller decrease across the pulmonary circulation wa s statistically insignificant. No decrease in the PSA concentration wa s noted across the renal circulation. The PSA concentration increased significantly (0.19 +/- 0.18 ng./ml. or 16.3%, p = 0.003) across the p elvic circulation, confirming the release of PSA from the prostate. Co nclusions: PSA is released from the prostate. The kidneys and lungs do not have a significant role in elimination of PSA, and the liver appe ars to be the most likely site of its metabolism. Although our sample size is small and the PSA range is narrow, our results strongly suppor t these conclusions.