Appearance of plasminogen activator activity during a synchronous cycle of a rat adenocarcinoma cell line, PA-III.

A study of the appearance of plasminogen activators during the cell cycle of a rat prostate adenocarcinoma cell line, PA-III, was undertaken. After release from a hydroxyurea (HU) block, the length of the cell cycle was determined and found to be 20-25 h, with the S-G2-M portions comprising approx. 10-15 h and the G1 phase occurring over a similar 10-15-h period. Assays for tissue-like plasminogen activator (t-PA) and urokinase-like plasminogen activator (u-PA) in cell-conditioned medium revealed an increased appearance of both enzymes shortly after the S phase of the cycle. The pattern of production of these activators remained the same under differing conditions of cell synchronization.