Plasminogen activator in prostatic tumors of Nb rats

Using a fluorometric assay, nonspecific proteolytic activity and plasminogen activator were measured in transplantable tumors of the dorsal prostate of Nb rats. Nonspecific proteolytic activity in prostatic tumors did not differ significantly from that measured in normal dorsal prostate, whereas plasminogen activator activity, undetectable in the latter tissue, was readily measurable in the tumors. Furthermore, plasminogen activator activity in prostatic tumors characterized by hormone-insensitive growth was 8-fold higher than in tumors characterized by androgen-stimulated growth. In both typess of tumors, the plasminogen activator activity per mg protein was highest in the lysosomal fractions. The results indicate that plasminogen activator may be a useful marker for discriminating between androgen-stimulated and autonomous prostatic tumors.